The Experts below are selected from a list of 1611 Experts worldwide ranked by ideXlab platform

Wenbin Hu - One of the best experts on this subject based on the ideXlab platform.

  • microstructure modification and improving corrosion resistance of laser surface quenched nickel Aluminum Bronze alloy
    Corrosion Science, 2020
    Co-Authors: Yiwen Zhang, Yuting Lv, Zhong Wu, Wenbin Hu
    Abstract:

    Abstract Laser surface quenching technology was utilized to modify the surface microstructure of as-cast nickel-Aluminum Bronze. A supersaturated solid solution layer with a fine-grained size of 30∼50 μm was formed, and its corrosion behavior was studied by electrochemical measurements and long-term immersion corrosion test. It was found that laser surface quenching homogenized the distribution of elements in the constituent phases and eliminated the selective phase corrosion. Due to the formation of a more protective film on laser quenched NAB alloy, the corrosion rate reduced about 42.6 % compared with that of as-cast NAB alloy.

  • microstructure design to improve the corrosion and cavitation corrosion resistance of a nickel Aluminum Bronze
    Corrosion Science, 2018
    Co-Authors: Qi Zhang, Zhong Wu, Bin Shen, Wenbin Hu
    Abstract:

    Abstract Microstructure evolution of the nickel-Aluminum Bronze alloy was studied by heat treatment, including annealing, normalizing, quenching and aging. The microstructure was refined and homogenized after quenching or quenching/aging at 450 ℃, which can eliminate selective phase corrosion effectively. Compared with the current production process, static corrosion rate reduced about 50%, due to the rapid formation of a protective film. In addition, cavitation corrosion rate reduced by a factor of 4.9 and 7.9 for the quenched and quenched/aged at 450 ℃ samples, respectively. This can be attributed to the improved hardness and weakened synergy between corrosion and mechanical attack.

  • the corrosion behavior of ni cu gradient layer on the nickel Aluminum Bronze nab alloy
    Corrosion Science, 2018
    Co-Authors: Zhong Wu, Wenbin Hu, Bin Shen
    Abstract:

    Abstract The gradient Ni-Cu layer on nickel Aluminum-Bronze alloy was obtained by the thermal diffusion process. The corrosion resistance was improved due to the formation of protective film, consisted of Ni(OH)2 and Cu2O. Although the Ni-Cu layer exhibited local corrosion with uniform corrosion and pitting corrosion simultaneously during the immersion test, the pitting growth was depressed because of the gradient distribution of Ni and Cu. The relieving driving force for galvanic corrosion between outer passive layer and bare Ni-Cu in the pitting was the main factor, which was caused by the decreasing interface potential drop.

  • the synergistic effect of cavitation erosion and corrosion of nickel Aluminum copper surface layer on nickel Aluminum Bronze alloy
    Journal of Alloys and Compounds, 2018
    Co-Authors: Qi Zhang, Zhong Wu, Wenbin Hu, Bin Shen
    Abstract:

    Abstract A completely nickel-Aluminum-copper (Ni-Al-Cu) layer was obtained through thermal diffusion process on a nickel-Aluminum-Bronze (NAB) substrate. The cumulative mass loss of the NAB alloy during the cavitation erosion tests was about 6.4 times and 5.5 times as large as that of the Ni-Al-Cu layer in distilled water and 3.5 wt% sodium chloride (NaCl), respectively. Electrochemical measurements under quiescence and cavitation erosion conditions were conducted to investigate the synergistic effects of cavitation erosion and corrosion. The results showed that the synergism had measurable effect on the cavitation erosion-corrosion process for both the NAB alloy and the Ni-Al-Cu layer. The total contribution of the cavitation erosion component including WE and WCIE was more than 80% and WE occupied the largest percentage. Thus, the improved cavitation erosion resistance of the Ni-Al-Cu layer was mainly due to mechanical factors, which implied a homogeneous and refined microstructure and the formation of hardened Ni3Al phase.

  • surface modification of nickel Aluminum Bronze alloy with gradient ni cu solid solution coating via thermal diffusion
    Surface & Coatings Technology, 2017
    Co-Authors: Zhong Wu, Wenbin Hu
    Abstract:

    Abstract The surface modification of nickel-Aluminum Bronze (NAB) alloy was developed by thermal diffusion of Ni coating and the alloy matrix. A multilayer coating was designed with the gradient outer layer of the Ni-Cu solid solution and the inner layer of the Ni-Al-Cu intermetallic layer. The evolution of the multilayer was a diffusion controlled model. The enhanced corrosion resistance of the Ni-Cu layer could be found in the salt spray test, which exhibited uniform corrosion behavior compared with severe selective phase corrosion of the NAB alloy. Besides the gradient distribution of the components, it was also attributed to the formation of protective film, which mainly consisted of Ni(OH) 2 and Cu 2 O. It has been confirmed by electrochemical impedance spectroscopy (EIS) test and X-ray photoelectron spectroscopy (XPS) results.

Mohsen Mohammadi - One of the best experts on this subject based on the ideXlab platform.

  • atom probe tomography study of κ phases in additively manufactured nickel Aluminum Bronze in as built and heat treated conditions
    Materials & Design, 2021
    Co-Authors: C Dharmendra, Babak Shalchi Amirkhiz, K P Rice, Mohsen Mohammadi
    Abstract:

    Abstract The distribution, morphology, and chemical composition of various κ-phases present in the wire-arc additive manufactured (WAAM) nickel Aluminum Bronze (NAB) of nominal composition Cu-9Al-4Ni-4Fe-1Mn (wt%) was investigated in the as-built and three different heat-treated conditions (350 °C for 2 h, 550 °C for 4 h, and 675 °C for 6 h). The precipitation of intermetallic κ-phases plays a crucial role in determining the mechanical and corrosion properties. The microstructural changes were analyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM) with energy dispersive spectroscopy (EDS), and complemented with atom probe tomography (APT) at the nano-scale. The as-built microstructure consists of copper-rich α, κII (globular Fe3Al) and κIII (lamellar NiAl) phases in the interdendritic regions, and nano-scale Fe-rich κIV particles (5–10 nm) in the Cu-matrix. Heat-treatment at 350 °C for 2 h (HT-1) has not produced any significant microstructural changes. When heat-treated at 550 °C for 4 h (HT-2), a new-phase needle-like κv (NiAl based) was formed, which differs from other κ-phases in morphology. After HT-2, globular κII was coarsened, lamellar κIII was partially spheroidized, and κIV precipitation in the matrix was reduced. Under conditions of 675 °C for 6 h (HT-3), globular κII and needle-like κv were coarsened, lamellar κIII was completely spheroidized, and the amount of κIV was significantly reduced.

  • wire arc additive manufactured nickel Aluminum Bronze with enhanced mechanical properties using heat treatments cycles
    Additive manufacturing, 2020
    Co-Authors: Chalasani Dharmendra, Babak Shalchi Amirkhiz, A Lloyd, G Janaki D Ram, Mohsen Mohammadi
    Abstract:

    Abstract Wire-arc additive manufacturing (WAAM) technique was used to develop nickel Aluminum Bronze (NAB) components for naval applications. The microstructural changes were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) with energy dispersive spectroscopy (EDS). As-built WAAM-NAB consists of κII (globular Fe3Al) and κIII (lamellar NiAl) phases in the interdendritic regions and fine Fe-rich κIV particles in the Cu-matrix. Along the build direction, the WAAM-NAB flat samples exhibited yield and ultimate tensile strength values of 380 and 708 MPa, respectively, and 34 % elongation. Furthermore, three different heat-treatments were performed on the samples in a view to evaluating their effect on mechanical properties. When heat-treated to 350 °C for 2 h (HT-1), there are no significant microstructural changes, and tensile properties along the build direction are similar to the as-built WAAM-NAB. Heat-treatment at 550 °C for 4 h (HT-2) produced a new needle-like κv phase in the α-matrix, coarsening of globular κII, partial spheroidization of lamellar κIII, and reduced amount of κIV precipitation. As compared to the WAAM-NAB, HT-2 samples exhibited a significant increase in yield strength (∼90 MPa), and ultimate tensile strength (∼60 MPa); however, tensile ductility was observed to drop by 20 %. After heat-treatment at 675 °C for 6 h (HT-3), globular κII and needle-like κv were coarsened, lamellar κIII was completely spheroidized, and the amount of κIV was significantly reduced. HT-3 samples showed better tensile strength (∼37 MPa) than the WAAM-NAB with marginal loss (6%) in the ductility.

  • wire arc additive manufacturing of nickel Aluminum Bronze stainless steel hybrid parts interfacial characterization prospects and problems
    Materialia, 2020
    Co-Authors: C Dharmendra, G Janaki D Ram, Sajad Shakerin, Mohsen Mohammadi
    Abstract:

    Abstract Hybrid parts of nickel Aluminum Bronze (NAB) and 316L stainless steel were fabricated using a commercially available wire-arc additive manufacturing (WAAM) technology to evaluate the feasibility and cracking tendency. Focused Ion beam (FIB) based Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Electron Backscatter Diffraction (EBSD), and Transmission Electron Microscopy (TEM) were used to characterize the built (NAB)-substrate (SS) interfacial characteristics. FIB extracted a selected region of the interface, and the spatial distribution of the interface across several sections was characterized by using the state-of-the-art technique for 3D EBSD mapping. A metallurgically bonded interface without any pores and cracks, with the inter-diffusion region in a thickness of 2 μm, was formed, which was further confirmed by a video with the results of 3D reconstructed EBSD maps. The interface did not exhibit any strong texture orientation owing to the control of the thermal gradient as NAB is more conductive than 316L. EDS elemental mapping confirmed that Fe3Al intermetallic was formed at the NAB/SS bimetallic-joint interface. Occasional liquation cracks on the grain boundaries in the heat-affected zone (HAZ) of 316L substrate were observed. Fe-Al based intermetallic formation, along with the penetration of copper along the HAZ cracks, was noticed. The problems associated were highlighted, and remedial measures were suggested to open up the possibilities of additive manufacturing to fabricate NAB-Stainless steel hybrid parts for industrial repair and maintenance applications.

  • micromechanical characterization of wire arc additive manufactured and cast nickel Aluminum Bronze ambient and intermediate temperatures
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2020
    Co-Authors: S I Shakil, Chalasani Dharmendra, Babak Shalchi Amirkhiz, D. Verma, Mohsen Mohammadi, Mahdiar Haghshenas
    Abstract:

    Abstract Instrumented indentation is a semi-destructive and robust technique to assess micromechanical characteristics (e.g., local properties) of metallic materials at ambient and elevated temperatures. In the present study, the instrumented indentation is employed to assess and compare the micromechanical response and fundamental mechanisms of plastic deformation (e.g., rate-controlling plasticity) in wire-arc additively manufactured (WAAM) and cast nickel Aluminum Bronze (Cu–9Al–4Fe–4Ni–1Mn) at ambient and intermediate temperatures. Two separate sets of indentation-based test schedules are employed to investigate these mechanisms. In the first set of experiments, load-controlled (peak load of 500 mN) indentation tests are performed under various loading rates (5–50 mN/s) at a constant (25 °C) temperature. In the second set of experiments, load-controlled indentation tests (peak load of 200 mN) at various temperatures of 25, 200, and 300 °C are performed under a constant loading rate. Indentation load versus indentation depth and time data are analyzed to collect a wealth of information including indentation stress, indentation strain rate, size effect, dislocation activation energy, and activation volume to assess fundamentals of governing mechanisms of plastic deformation. Optical, scanning, and transmission electron microscopy are utilized to provide microstructural evidence for the proposed micromechanical mechanisms of plastic deformation based on dislocation activities and interactions. The nanoindentation hardness results show that the strength of the WAAM alloy is higher than the cast counterpart. However, neither cast nor WAAM-NAB materials are rate-sensitive at ambient (room) temperature. When the temperature is raised, both alloys become softer, and the indentation size effect becomes less pronounced. The activation volume and the activation energy data show that a steady-state microstructure does not necessarily exist around the indentations, and the nature of rate-limiting obstacles (against dislocation activities) may vary in the course of the indentation.

  • microstructural evolution and mechanical behavior of nickel Aluminum Bronze cu 9al 4fe 4ni 1mn fabricated through wire arc additive manufacturing
    Additive manufacturing, 2019
    Co-Authors: Chalasani Dharmendra, Amir Hadadzadeh, Babak Shalchi Amirkhiz, Mohsen Mohammadi
    Abstract:

    Abstract As a step forward toward the development of the next generation of nickel Aluminum Bronze (NAB) components using wire-arc additive manufacturing (WAAM), square bars were printed in the vertical direction. The as-built microstructure was characterized using multi-scale electron microscopy techniques, where the differences in phase formation were compared to the reference cast-NAB based on the solidification characteristics. The as-cast microstructure typically consists of Cu-rich α-matrix, and four types of intermetallic particles referred to as κ-phases. In the WAAM-NAB, the formation of κI was suppressed due to high cooling rates. The microstructure was finer and the volume fraction of intermetallic particles was significantly lower than that of the cast-NAB. Based on energy dispersive spectroscopy (EDS) technique and diffraction pattern analysis using transmission electron microscopy (TEM), the phases formed in the interdendritic regions were identified as κII (globular Fe3Al) and κIII (lamellar NiAl), whereas numerous fine (5–10 nm) Fe-rich κIV particles were precipitated uniformly within the α-matrix. Electron backscatter diffraction analysis revealed weak texture on both parallel and perpendicular planes to the building direction with (100) poles rotated away from the build direction. The WAAM-NAB sample exhibited considerably higher yield strength (˜88 MPa) and elongation (˜10%) than the cast-NAB, but the gain in the ultimate tensile strength was marginal.

Babak Shalchi Amirkhiz - One of the best experts on this subject based on the ideXlab platform.

  • atom probe tomography study of κ phases in additively manufactured nickel Aluminum Bronze in as built and heat treated conditions
    Materials & Design, 2021
    Co-Authors: C Dharmendra, Babak Shalchi Amirkhiz, K P Rice, Mohsen Mohammadi
    Abstract:

    Abstract The distribution, morphology, and chemical composition of various κ-phases present in the wire-arc additive manufactured (WAAM) nickel Aluminum Bronze (NAB) of nominal composition Cu-9Al-4Ni-4Fe-1Mn (wt%) was investigated in the as-built and three different heat-treated conditions (350 °C for 2 h, 550 °C for 4 h, and 675 °C for 6 h). The precipitation of intermetallic κ-phases plays a crucial role in determining the mechanical and corrosion properties. The microstructural changes were analyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM) with energy dispersive spectroscopy (EDS), and complemented with atom probe tomography (APT) at the nano-scale. The as-built microstructure consists of copper-rich α, κII (globular Fe3Al) and κIII (lamellar NiAl) phases in the interdendritic regions, and nano-scale Fe-rich κIV particles (5–10 nm) in the Cu-matrix. Heat-treatment at 350 °C for 2 h (HT-1) has not produced any significant microstructural changes. When heat-treated at 550 °C for 4 h (HT-2), a new-phase needle-like κv (NiAl based) was formed, which differs from other κ-phases in morphology. After HT-2, globular κII was coarsened, lamellar κIII was partially spheroidized, and κIV precipitation in the matrix was reduced. Under conditions of 675 °C for 6 h (HT-3), globular κII and needle-like κv were coarsened, lamellar κIII was completely spheroidized, and the amount of κIV was significantly reduced.

  • wire arc additive manufactured nickel Aluminum Bronze with enhanced mechanical properties using heat treatments cycles
    Additive manufacturing, 2020
    Co-Authors: Chalasani Dharmendra, Babak Shalchi Amirkhiz, A Lloyd, G Janaki D Ram, Mohsen Mohammadi
    Abstract:

    Abstract Wire-arc additive manufacturing (WAAM) technique was used to develop nickel Aluminum Bronze (NAB) components for naval applications. The microstructural changes were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) with energy dispersive spectroscopy (EDS). As-built WAAM-NAB consists of κII (globular Fe3Al) and κIII (lamellar NiAl) phases in the interdendritic regions and fine Fe-rich κIV particles in the Cu-matrix. Along the build direction, the WAAM-NAB flat samples exhibited yield and ultimate tensile strength values of 380 and 708 MPa, respectively, and 34 % elongation. Furthermore, three different heat-treatments were performed on the samples in a view to evaluating their effect on mechanical properties. When heat-treated to 350 °C for 2 h (HT-1), there are no significant microstructural changes, and tensile properties along the build direction are similar to the as-built WAAM-NAB. Heat-treatment at 550 °C for 4 h (HT-2) produced a new needle-like κv phase in the α-matrix, coarsening of globular κII, partial spheroidization of lamellar κIII, and reduced amount of κIV precipitation. As compared to the WAAM-NAB, HT-2 samples exhibited a significant increase in yield strength (∼90 MPa), and ultimate tensile strength (∼60 MPa); however, tensile ductility was observed to drop by 20 %. After heat-treatment at 675 °C for 6 h (HT-3), globular κII and needle-like κv were coarsened, lamellar κIII was completely spheroidized, and the amount of κIV was significantly reduced. HT-3 samples showed better tensile strength (∼37 MPa) than the WAAM-NAB with marginal loss (6%) in the ductility.

  • micromechanical characterization of wire arc additive manufactured and cast nickel Aluminum Bronze ambient and intermediate temperatures
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2020
    Co-Authors: S I Shakil, Chalasani Dharmendra, Babak Shalchi Amirkhiz, D. Verma, Mohsen Mohammadi, Mahdiar Haghshenas
    Abstract:

    Abstract Instrumented indentation is a semi-destructive and robust technique to assess micromechanical characteristics (e.g., local properties) of metallic materials at ambient and elevated temperatures. In the present study, the instrumented indentation is employed to assess and compare the micromechanical response and fundamental mechanisms of plastic deformation (e.g., rate-controlling plasticity) in wire-arc additively manufactured (WAAM) and cast nickel Aluminum Bronze (Cu–9Al–4Fe–4Ni–1Mn) at ambient and intermediate temperatures. Two separate sets of indentation-based test schedules are employed to investigate these mechanisms. In the first set of experiments, load-controlled (peak load of 500 mN) indentation tests are performed under various loading rates (5–50 mN/s) at a constant (25 °C) temperature. In the second set of experiments, load-controlled indentation tests (peak load of 200 mN) at various temperatures of 25, 200, and 300 °C are performed under a constant loading rate. Indentation load versus indentation depth and time data are analyzed to collect a wealth of information including indentation stress, indentation strain rate, size effect, dislocation activation energy, and activation volume to assess fundamentals of governing mechanisms of plastic deformation. Optical, scanning, and transmission electron microscopy are utilized to provide microstructural evidence for the proposed micromechanical mechanisms of plastic deformation based on dislocation activities and interactions. The nanoindentation hardness results show that the strength of the WAAM alloy is higher than the cast counterpart. However, neither cast nor WAAM-NAB materials are rate-sensitive at ambient (room) temperature. When the temperature is raised, both alloys become softer, and the indentation size effect becomes less pronounced. The activation volume and the activation energy data show that a steady-state microstructure does not necessarily exist around the indentations, and the nature of rate-limiting obstacles (against dislocation activities) may vary in the course of the indentation.

  • microstructural evolution and mechanical behavior of nickel Aluminum Bronze cu 9al 4fe 4ni 1mn fabricated through wire arc additive manufacturing
    Additive manufacturing, 2019
    Co-Authors: Chalasani Dharmendra, Amir Hadadzadeh, Babak Shalchi Amirkhiz, Mohsen Mohammadi
    Abstract:

    Abstract As a step forward toward the development of the next generation of nickel Aluminum Bronze (NAB) components using wire-arc additive manufacturing (WAAM), square bars were printed in the vertical direction. The as-built microstructure was characterized using multi-scale electron microscopy techniques, where the differences in phase formation were compared to the reference cast-NAB based on the solidification characteristics. The as-cast microstructure typically consists of Cu-rich α-matrix, and four types of intermetallic particles referred to as κ-phases. In the WAAM-NAB, the formation of κI was suppressed due to high cooling rates. The microstructure was finer and the volume fraction of intermetallic particles was significantly lower than that of the cast-NAB. Based on energy dispersive spectroscopy (EDS) technique and diffraction pattern analysis using transmission electron microscopy (TEM), the phases formed in the interdendritic regions were identified as κII (globular Fe3Al) and κIII (lamellar NiAl), whereas numerous fine (5–10 nm) Fe-rich κIV particles were precipitated uniformly within the α-matrix. Electron backscatter diffraction analysis revealed weak texture on both parallel and perpendicular planes to the building direction with (100) poles rotated away from the build direction. The WAAM-NAB sample exhibited considerably higher yield strength (˜88 MPa) and elongation (˜10%) than the cast-NAB, but the gain in the ultimate tensile strength was marginal.

  • the morphology crystallography and chemistry of phases in wire arc additively manufactured nickel Aluminum Bronze
    2019
    Co-Authors: Chalasani Dharmendra, Amir Hadadzadeh, Babak Shalchi Amirkhiz, Mohsen Mohammadi
    Abstract:

    A new Wire-Arc Additive Manufacturing (WAAM) technique is used to produce Nickel Aluminum Bronze (NAB) components for marine applications in view to mitigate the problems that typically arise in a cast microstructure. In cast condition, the alloy typically exhibits microstructure that consists of an FCC Cu-rich solid solution (or α-phase), some retained β-phase, and several intermetallic phases collectively referred to as κ-phase. This study aims to characterize the crystal structures of the various κ-phases or precipitates, their distribution, morphology, orientation relationships with the α-matrix, and their chemical compositions in WAAM-NAB alloy using electron microscopy. The precipitation of κ-phase differs in morphology and chemical composition to those present in a cast NAB. In addition, some uniaxial tensile coupons were machined out of the WAAM-NAB samples, where tensile mechanical properties are superior to those of cast NAB. The effects of microstructural differences in both alloys on the mechanical properties are correlated.

Zhong Wu - One of the best experts on this subject based on the ideXlab platform.

  • microstructure modification and improving corrosion resistance of laser surface quenched nickel Aluminum Bronze alloy
    Corrosion Science, 2020
    Co-Authors: Yiwen Zhang, Yuting Lv, Zhong Wu, Wenbin Hu
    Abstract:

    Abstract Laser surface quenching technology was utilized to modify the surface microstructure of as-cast nickel-Aluminum Bronze. A supersaturated solid solution layer with a fine-grained size of 30∼50 μm was formed, and its corrosion behavior was studied by electrochemical measurements and long-term immersion corrosion test. It was found that laser surface quenching homogenized the distribution of elements in the constituent phases and eliminated the selective phase corrosion. Due to the formation of a more protective film on laser quenched NAB alloy, the corrosion rate reduced about 42.6 % compared with that of as-cast NAB alloy.

  • evolution of the corrosion product film on nickel Aluminum Bronze and its corrosion behavior in 3 5 wt nacl solution
    Materials, 2019
    Co-Authors: Yang Ding, Rong Zhao, Zhong Wu, Liqiang Wang, Weijie Lu
    Abstract:

    The in-situ studies of the corrosion product film on nickel-Aluminum Bronze are significant for explaining the mechanism of its corrosion resistance. In this paper, the corrosion behavior of nickel-Aluminum Bronze and the formation process of the protective film in 3.5 wt % NaCl solution are systematically investigated. The results of scanning electron microscope analysis and electrochemical tests indicate that the corrosion resistance of nickel-Aluminum Bronze is improved due to the formation of the corrosion product film. The change of local electrochemical property on the corrosion product film during the immersion time is evaluated via in-situ scanning vibrating electrode technique, and it reveals the evolution rules of ionic flux in real time. The formation process of the protective film on different phases in nickel-Aluminum Bronze is observed directly by in-situ atomic force microscopy as height change measurements. The α phases at different locations present different corrosion behaviors, and the lamellar α phase within the α + κIII eutectoid structure gets more serious corrosion attack. The κ phases establish a stable and dense protective film in short time, preventing the corrosion attack effectively. The β′ phase, however, suffers the most serious corrosion damage until a protective film is formed after 150 min of immersion.

  • microstructure design to improve the corrosion and cavitation corrosion resistance of a nickel Aluminum Bronze
    Corrosion Science, 2018
    Co-Authors: Qi Zhang, Zhong Wu, Bin Shen, Wenbin Hu
    Abstract:

    Abstract Microstructure evolution of the nickel-Aluminum Bronze alloy was studied by heat treatment, including annealing, normalizing, quenching and aging. The microstructure was refined and homogenized after quenching or quenching/aging at 450 ℃, which can eliminate selective phase corrosion effectively. Compared with the current production process, static corrosion rate reduced about 50%, due to the rapid formation of a protective film. In addition, cavitation corrosion rate reduced by a factor of 4.9 and 7.9 for the quenched and quenched/aged at 450 ℃ samples, respectively. This can be attributed to the improved hardness and weakened synergy between corrosion and mechanical attack.

  • the corrosion behavior of ni cu gradient layer on the nickel Aluminum Bronze nab alloy
    Corrosion Science, 2018
    Co-Authors: Zhong Wu, Wenbin Hu, Bin Shen
    Abstract:

    Abstract The gradient Ni-Cu layer on nickel Aluminum-Bronze alloy was obtained by the thermal diffusion process. The corrosion resistance was improved due to the formation of protective film, consisted of Ni(OH)2 and Cu2O. Although the Ni-Cu layer exhibited local corrosion with uniform corrosion and pitting corrosion simultaneously during the immersion test, the pitting growth was depressed because of the gradient distribution of Ni and Cu. The relieving driving force for galvanic corrosion between outer passive layer and bare Ni-Cu in the pitting was the main factor, which was caused by the decreasing interface potential drop.

  • the synergistic effect of cavitation erosion and corrosion of nickel Aluminum copper surface layer on nickel Aluminum Bronze alloy
    Journal of Alloys and Compounds, 2018
    Co-Authors: Qi Zhang, Zhong Wu, Wenbin Hu, Bin Shen
    Abstract:

    Abstract A completely nickel-Aluminum-copper (Ni-Al-Cu) layer was obtained through thermal diffusion process on a nickel-Aluminum-Bronze (NAB) substrate. The cumulative mass loss of the NAB alloy during the cavitation erosion tests was about 6.4 times and 5.5 times as large as that of the Ni-Al-Cu layer in distilled water and 3.5 wt% sodium chloride (NaCl), respectively. Electrochemical measurements under quiescence and cavitation erosion conditions were conducted to investigate the synergistic effects of cavitation erosion and corrosion. The results showed that the synergism had measurable effect on the cavitation erosion-corrosion process for both the NAB alloy and the Ni-Al-Cu layer. The total contribution of the cavitation erosion component including WE and WCIE was more than 80% and WE occupied the largest percentage. Thus, the improved cavitation erosion resistance of the Ni-Al-Cu layer was mainly due to mechanical factors, which implied a homogeneous and refined microstructure and the formation of hardened Ni3Al phase.

Chalasani Dharmendra - One of the best experts on this subject based on the ideXlab platform.

  • wire arc additive manufactured nickel Aluminum Bronze with enhanced mechanical properties using heat treatments cycles
    Additive manufacturing, 2020
    Co-Authors: Chalasani Dharmendra, Babak Shalchi Amirkhiz, A Lloyd, G Janaki D Ram, Mohsen Mohammadi
    Abstract:

    Abstract Wire-arc additive manufacturing (WAAM) technique was used to develop nickel Aluminum Bronze (NAB) components for naval applications. The microstructural changes were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) with energy dispersive spectroscopy (EDS). As-built WAAM-NAB consists of κII (globular Fe3Al) and κIII (lamellar NiAl) phases in the interdendritic regions and fine Fe-rich κIV particles in the Cu-matrix. Along the build direction, the WAAM-NAB flat samples exhibited yield and ultimate tensile strength values of 380 and 708 MPa, respectively, and 34 % elongation. Furthermore, three different heat-treatments were performed on the samples in a view to evaluating their effect on mechanical properties. When heat-treated to 350 °C for 2 h (HT-1), there are no significant microstructural changes, and tensile properties along the build direction are similar to the as-built WAAM-NAB. Heat-treatment at 550 °C for 4 h (HT-2) produced a new needle-like κv phase in the α-matrix, coarsening of globular κII, partial spheroidization of lamellar κIII, and reduced amount of κIV precipitation. As compared to the WAAM-NAB, HT-2 samples exhibited a significant increase in yield strength (∼90 MPa), and ultimate tensile strength (∼60 MPa); however, tensile ductility was observed to drop by 20 %. After heat-treatment at 675 °C for 6 h (HT-3), globular κII and needle-like κv were coarsened, lamellar κIII was completely spheroidized, and the amount of κIV was significantly reduced. HT-3 samples showed better tensile strength (∼37 MPa) than the WAAM-NAB with marginal loss (6%) in the ductility.

  • micromechanical characterization of wire arc additive manufactured and cast nickel Aluminum Bronze ambient and intermediate temperatures
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2020
    Co-Authors: S I Shakil, Chalasani Dharmendra, Babak Shalchi Amirkhiz, D. Verma, Mohsen Mohammadi, Mahdiar Haghshenas
    Abstract:

    Abstract Instrumented indentation is a semi-destructive and robust technique to assess micromechanical characteristics (e.g., local properties) of metallic materials at ambient and elevated temperatures. In the present study, the instrumented indentation is employed to assess and compare the micromechanical response and fundamental mechanisms of plastic deformation (e.g., rate-controlling plasticity) in wire-arc additively manufactured (WAAM) and cast nickel Aluminum Bronze (Cu–9Al–4Fe–4Ni–1Mn) at ambient and intermediate temperatures. Two separate sets of indentation-based test schedules are employed to investigate these mechanisms. In the first set of experiments, load-controlled (peak load of 500 mN) indentation tests are performed under various loading rates (5–50 mN/s) at a constant (25 °C) temperature. In the second set of experiments, load-controlled indentation tests (peak load of 200 mN) at various temperatures of 25, 200, and 300 °C are performed under a constant loading rate. Indentation load versus indentation depth and time data are analyzed to collect a wealth of information including indentation stress, indentation strain rate, size effect, dislocation activation energy, and activation volume to assess fundamentals of governing mechanisms of plastic deformation. Optical, scanning, and transmission electron microscopy are utilized to provide microstructural evidence for the proposed micromechanical mechanisms of plastic deformation based on dislocation activities and interactions. The nanoindentation hardness results show that the strength of the WAAM alloy is higher than the cast counterpart. However, neither cast nor WAAM-NAB materials are rate-sensitive at ambient (room) temperature. When the temperature is raised, both alloys become softer, and the indentation size effect becomes less pronounced. The activation volume and the activation energy data show that a steady-state microstructure does not necessarily exist around the indentations, and the nature of rate-limiting obstacles (against dislocation activities) may vary in the course of the indentation.

  • microstructural evolution and mechanical behavior of nickel Aluminum Bronze cu 9al 4fe 4ni 1mn fabricated through wire arc additive manufacturing
    Additive manufacturing, 2019
    Co-Authors: Chalasani Dharmendra, Amir Hadadzadeh, Babak Shalchi Amirkhiz, Mohsen Mohammadi
    Abstract:

    Abstract As a step forward toward the development of the next generation of nickel Aluminum Bronze (NAB) components using wire-arc additive manufacturing (WAAM), square bars were printed in the vertical direction. The as-built microstructure was characterized using multi-scale electron microscopy techniques, where the differences in phase formation were compared to the reference cast-NAB based on the solidification characteristics. The as-cast microstructure typically consists of Cu-rich α-matrix, and four types of intermetallic particles referred to as κ-phases. In the WAAM-NAB, the formation of κI was suppressed due to high cooling rates. The microstructure was finer and the volume fraction of intermetallic particles was significantly lower than that of the cast-NAB. Based on energy dispersive spectroscopy (EDS) technique and diffraction pattern analysis using transmission electron microscopy (TEM), the phases formed in the interdendritic regions were identified as κII (globular Fe3Al) and κIII (lamellar NiAl), whereas numerous fine (5–10 nm) Fe-rich κIV particles were precipitated uniformly within the α-matrix. Electron backscatter diffraction analysis revealed weak texture on both parallel and perpendicular planes to the building direction with (100) poles rotated away from the build direction. The WAAM-NAB sample exhibited considerably higher yield strength (˜88 MPa) and elongation (˜10%) than the cast-NAB, but the gain in the ultimate tensile strength was marginal.

  • the morphology crystallography and chemistry of phases in wire arc additively manufactured nickel Aluminum Bronze
    2019
    Co-Authors: Chalasani Dharmendra, Amir Hadadzadeh, Babak Shalchi Amirkhiz, Mohsen Mohammadi
    Abstract:

    A new Wire-Arc Additive Manufacturing (WAAM) technique is used to produce Nickel Aluminum Bronze (NAB) components for marine applications in view to mitigate the problems that typically arise in a cast microstructure. In cast condition, the alloy typically exhibits microstructure that consists of an FCC Cu-rich solid solution (or α-phase), some retained β-phase, and several intermetallic phases collectively referred to as κ-phase. This study aims to characterize the crystal structures of the various κ-phases or precipitates, their distribution, morphology, orientation relationships with the α-matrix, and their chemical compositions in WAAM-NAB alloy using electron microscopy. The precipitation of κ-phase differs in morphology and chemical composition to those present in a cast NAB. In addition, some uniaxial tensile coupons were machined out of the WAAM-NAB samples, where tensile mechanical properties are superior to those of cast NAB. The effects of microstructural differences in both alloys on the mechanical properties are correlated.