The Experts below are selected from a list of 13149 Experts worldwide ranked by ideXlab platform

R D K Misra - One of the best experts on this subject based on the ideXlab platform.

  • hydrogen diffusivity in different microstructural components in martensite matrix with retained austenite
    International Journal of Hydrogen Energy, 2020
    Co-Authors: Xiuhua Gao, Liangyun Lan, R D K Misra
    Abstract:

    Abstract We elucidate the hydrogen diffusivity in martensite matrix with retained austenite (RA). Two aspects are focused: effect of microstructure on hydrogen diffusion behavior; hydrogen diffusivity calculation for different microstructural components. Quenched martensite (QM) had the Highest effective hydrogen diffusion coefficient because of High Dislocation Density. Effective hydrogen diffusion coefficient decreased with the increase of intercritical annealing temperature because of decrease in Dislocation Density and increase of RA. According to the principle of Maxwell-Garnett equation, the hydrogen diffusion coefficient for grain boundary (GB) was 7.99 × 10−8 m2/s and hydrogen diffusion coefficient of tempered martensite (TM) was 7.84 × 10−11 m2/s.

  • microstructure mechanical property relationship and austenite stability in medium mn trip steels the effect of austenite reverted transformation and quenching tempering treatments
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2017
    Co-Authors: Z C Li, H. Ding, R D K Misra
    Abstract:

    Abstract In the present study, we fundamentally explore the reasons underlying differences in mechanical properties in hot-rolled 0.2C-1.6Al-6.1Mn-Fe TRIP steels subjected to different heat treatments. Comparing with austenite reverted transformation annealing (ART) process, quenching and tempering (QT [ART (UTS: 885–945MPa, TEL: 13–28%)]. In the ART process, long time annealing led to excessive C and Mn enrichment in austenite, which rendered austenite too stable and deteriorated TRIP effect. Furthermore, long time annealing reduced Dislocation Density and led to low work-hardening rate. The Q&T process enabled appropriate enrichment of elements and hence desired stability for significant TRIP effect to be observed. Thus, the steel quenched from 625 °C exhibited best combination of mechanical properties (UTS: 1038 MPa, TEL: 42%, UTS×TEL: 43.6 GPa%) because of significant contribution of TRIP effect and High Dislocation Density in austenite.

  • ultrafine grained al 0 2sc 0 1zr alloy the mechanistic contribution of nano sized precipitates on grain refinement during the novel process of accumulative continuous extrusion
    Acta Materialia, 2015
    Co-Authors: Yongfeng F Shen, Renguo Guan, Z Y Zhao, R D K Misra
    Abstract:

    Abstract We elucidate the potential significance of nanosized, Al 3 (Sc, Zr), precipitates in obtaining ultrafine-grained structure in an Al–0.2Sc–0.1Zr alloy during the novel process, referred as accumulative continuous extrusion forming (ACEF). The grain size of the alloy was dramatically refined from 100 μm to 800 nm through continuous dynamic recrystallization (CDRX). The effectiveness of nanosized precipitates on CDRX was pronounced with increase in the ratio of the volume fraction ( F v ) to the diameter ( d ) of the Al 3 (Sc, Zr) precipitates. Nanosized Al 3 (Sc, Zr), precipitates promoted grain refinement through three mechanisms: (i) the precipitates facilitated retention of High Dislocation Density in the alloy by promoting the generation of Dislocation and pinning Dislocation slip, which increased the driving force for CDRX, (ii) promoted the formation of deformation bands, providing sites for activation of CDRX, and (iii) activated CDRX near the grain boundary.

  • microstructure and properties of low manganese and niobium containing hic pipeline steel
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008
    Co-Authors: S S Nayak, R D K Misra, J E Hartmann, Fulvio Siciliano, J M Gray
    Abstract:

    Abstract The paper describes the concept of using low manganese content in pipeline steels for hydrogen-induced cracking (HIC) applications. The microstructure of thermomechanically processed pipeline steel primarily consisted of polygonal ferrite and low fraction of pearlite. The cleanliness of the steel was evident as was the absence of centerline segregation. The microstructure contained High Dislocation Density, sub-boundaries and Dislocation substructures. Fine-scale precipitation of niobium carbides occurred on parallel array of Dislocations and on random Dislocations that followed [0 0 1] NbC //[0 0 1] α-Fe relationship with the ferrite matrix.

M X Huang - One of the best experts on this subject based on the ideXlab platform.

  • the role of interstitial carbon atoms on the strain hardening rate of twinning induced plasticity steels
    Scripta Materialia, 2020
    Co-Authors: Z C Luo, M X Huang
    Abstract:

    Abstract Synchrotron X-ray diffraction was applied to measure the Dislocation Density of two twinning-induced plasticity (TWIP) steels with different carbon content but comparable stacking fault energy (SFE). We found that the Dislocation Density of the carbon-alloyed TWIP is much Higher than that of the carbon-free TWIP steel, though these two steels possess similar twin volume fraction. It indicates that the excellent tensile and strain-hardening properties of the carbon-alloyed TWIP steels are mainly caused by the High Dislocation Density induced by the carbon-Dislocation interaction. Carbon-free TWIP steels are conventional low SFE fcc alloys similar to 316L stainless steel.

  • revisit the role of deformation twins on the work hardening behaviour of twinning induced plasticity steels
    Scripta Materialia, 2018
    Co-Authors: Z C Luo, M X Huang
    Abstract:

    Abstract The present study found that the work-hardening rate and Dislocation Density in a twinning-induced plasticity (TWIP) steel deformed at 373 K and 473 K are comparable to that deformed at 298 K, but deformation twins are considerably prohibited at 373 and 473 K. High Dislocation Density induced by dynamic strain aging (DSA) is the dominant mechanism responsible for the High work-hardening rate of TWIP steels at 373 and 473 K. It indicates that TWIP steels can also achieve High working-hardening rate without the formation of deformation twins.

  • High Dislocation Density induced large ductility in deformed and partitioned steels
    Science, 2017
    Co-Authors: Hungwei Yen, G Cheng, Zuankai Wang, Haiwen Luo, M X Huang
    Abstract:

    A wide variety of industrial applications require materials with High strength and ductility. Unfortunately, the strategies for increasing material strength, such as processing to create line defects (Dislocations), tend to decrease ductility. We developed a strategy to circumvent this in inexpensive, medium manganese steel. Cold rolling followed by low-temperature tempering developed steel with metastable austenite grains embedded in a Highly dislocated martensite matrix. This deformed and partitioned (D and P) process produced Dislocation hardening but retained High ductility, both through the glide of intensive mobile Dislocations and by allowing us to control martensitic transformation. The D and P strategy should apply to any other alloy with deformation-induced martensitic transformation and provides a pathway for the development of High-strength, High-ductility materials.

Jamie J Kruzic - One of the best experts on this subject based on the ideXlab platform.

  • the effect of microstructure and welding induced plasticity on the strength of ni mo cr alloy welds
    Materialia, 2021
    Co-Authors: A E Danon, Ondrej Muransky, Hanliang Zhu, Tao Wei, Emmanuel Alejandro Floresjohnson, Jamie J Kruzic
    Abstract:

    Abstract The mechanical performance of a Ni–Mo–Cr (GH3535) alloy weldment, produced using a matching filler metal, was assessed and compared to the surrounding parent metal. Ambient-temperature mechanical characterisation included hardness testing, small punch testing and uniaxial tensile testing, while a crystal plasticity finite element model was used to assess the impact of crystallographic texture on the mechanical properties. Despite the similar chemical composition, the weld metal exhibited superior strength and ductility to that of the parent metal. The Higher strength was primarily attributed to the High Dislocation Density in the weld metal imbued by the welding-induced thermo-mechanical loading. In contrast, the ductility difference was attributed to M6C carbide stringers in the parent metal that initiated fracture at lower strains when compared to the weld metal, with the latter containing finer, well-dispersed M6C carbides.

  • the effect of microstructure and welding induced plasticity on the strength of ni mo cr alloy welds
    Social Science Research Network, 2020
    Co-Authors: A E Danon, Ondrej Muransky, Hanliang Zhu, Tao Wei, Emmanuel Alejandro Floresjohnson, Jamie J Kruzic
    Abstract:

    The mechanical performance of a Ni–Mo–Cr (GH3535) alloy weldment, produced using a matching filler metal, was assessed and compared to the surrounding parent metal. Ambient-temperature mechanical characterisation included hardness testing, small punch testing and uniaxial tensile testing, while a crystal plasticity finite element model was used to assess the impact of crystallographic texture on the mechanical properties. Despite the similar chemical composition, the weld metal exhibited superior strength and ductility to that of the parent metal. The Higher strength was primarily attributed to the High Dislocation Density in the weld metal imbued by the welding-induced thermo-mechanical loading. In contrast, the ductility difference was attributed to M6C carbide stringers in the parent metal that initiated fracture at lower strains than for the weld metal, with the latter containing much finer, well-dispersed M6C carbides.

R Z Valiev - One of the best experts on this subject based on the ideXlab platform.

  • microstructure and martensitic transformation of an ultrafine grained tininb shape memory alloy processed by equal channel angular pressing
    Intermetallics, 2014
    Co-Authors: Y X Tong, P C Jiang, F Chen, B Tian, Li Li, Yufeng Zheng, D V Gunderov, R Z Valiev
    Abstract:

    Microstructure, martensitic transformation and mechanical properties of an ultrafine-grained Ti44Ni47Nb9 shape memory alloy processed by equal channel angular pressing were investigated. The as-ECAP processed sample is characterized by an inhomogeneous and refined microstructure. In b-Nb phase-rich region, the grains of matrix are elongated with High Density Dislocations. In b-Nb phase-free region, the microstructure is partial recovery and characterized by near-equiaxed grains. The heterogeneous microstructure is attributed to presence of b-Nb phase. Martensitic transformation behavior of the as-ECAP processed sample is characterized by a single-stage transformation. The thermal cycling stability of transformation and the mechanical properties are considerably improved due to a strengthening effect resulting from refined grain size and High Dislocation Density.

  • processing nanocrystalline ti and its nanocomposites from micrometer sized ti powder using High pressure torsion
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2000
    Co-Authors: V V Stolyarov, T C Lowe, R K Islamgaliev, R Z Valiev
    Abstract:

    Abstract Nanocrystalline Ti and Ti–TiO 2 nanocomposites were produced by High pressure torsion (HPT) of precompacts of Ti powder (21 μm) and its mixture with TiO 2 powder (36 nm). Effects of processing temperature and pressure on material Density and microhardness were systematically studied. The HPT process simultaneously consolidated the Ti and Ti–TiO 2 powders and refined the grains to nanometer size. The microstructure of as-processed samples contained High Dislocation Density, High internal stress, High angle, non-equilibrium grain boundaries, and texture. Mechanical properties such as microhardness increased with increasing Density. Tensile testing showed that the as-processed materials were very brittle. High pressure torsion was found to be a promising technique for producing nanocrystalline materials from micrometer-sized metallic powders.

A E Danon - One of the best experts on this subject based on the ideXlab platform.

  • the effect of microstructure and welding induced plasticity on the strength of ni mo cr alloy welds
    Materialia, 2021
    Co-Authors: A E Danon, Ondrej Muransky, Hanliang Zhu, Tao Wei, Emmanuel Alejandro Floresjohnson, Jamie J Kruzic
    Abstract:

    Abstract The mechanical performance of a Ni–Mo–Cr (GH3535) alloy weldment, produced using a matching filler metal, was assessed and compared to the surrounding parent metal. Ambient-temperature mechanical characterisation included hardness testing, small punch testing and uniaxial tensile testing, while a crystal plasticity finite element model was used to assess the impact of crystallographic texture on the mechanical properties. Despite the similar chemical composition, the weld metal exhibited superior strength and ductility to that of the parent metal. The Higher strength was primarily attributed to the High Dislocation Density in the weld metal imbued by the welding-induced thermo-mechanical loading. In contrast, the ductility difference was attributed to M6C carbide stringers in the parent metal that initiated fracture at lower strains when compared to the weld metal, with the latter containing finer, well-dispersed M6C carbides.

  • the effect of microstructure and welding induced plasticity on the strength of ni mo cr alloy welds
    Social Science Research Network, 2020
    Co-Authors: A E Danon, Ondrej Muransky, Hanliang Zhu, Tao Wei, Emmanuel Alejandro Floresjohnson, Jamie J Kruzic
    Abstract:

    The mechanical performance of a Ni–Mo–Cr (GH3535) alloy weldment, produced using a matching filler metal, was assessed and compared to the surrounding parent metal. Ambient-temperature mechanical characterisation included hardness testing, small punch testing and uniaxial tensile testing, while a crystal plasticity finite element model was used to assess the impact of crystallographic texture on the mechanical properties. Despite the similar chemical composition, the weld metal exhibited superior strength and ductility to that of the parent metal. The Higher strength was primarily attributed to the High Dislocation Density in the weld metal imbued by the welding-induced thermo-mechanical loading. In contrast, the ductility difference was attributed to M6C carbide stringers in the parent metal that initiated fracture at lower strains than for the weld metal, with the latter containing much finer, well-dispersed M6C carbides.