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Ruishan Xin - One of the best experts on this subject based on the ideXlab platform.
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effect of deformation modes and heat treatment on microstructure and impact property restoration of Internal Crack healing in sa 508 steel
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2020Co-Authors: Yao Qiu, Ruishan Xin, Jianbin LuoAbstract:Abstract In this study, the effects of deformation modes and quenching and tempering (Q&T) process on the Crack healing and percentage recovery of impact properties were studied. The microstructure, Charpy impact properties and fracture surface morphology of the Crack zones at different healing stages were evaluated. When the healing temperatures was 950 °C and 1050 °C, percentage recovery of impact properties of the Internal Crack healing by multi-pass thermal deformation (twice upsetting and once drawing) was lower than that by uniaxial compression. After deformed by twice upsetting and once drawing at 1150 °C, the ‘Z type’ newly formed grain belt was observed in the Crack healing zone, which showed high resistance to the dynamic load. After Q&T process, the microstructure was evolved into the tempered bainite, and residual austenite decomposed gradually to carbides, precipitating out mainly along the grain boundaries. After Q&T process, the impact toughness of the Crack healing zones were improved, but the percentage recovery decreased, it is because that in the Crack healing zone, the carbides aggregated in the line, which has a lower resistance to applied force than the matrix.
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effects of heat treatment method on microstructure and mechanical properties of Internal Crack healing in sa 508 3 steel
2020Co-Authors: Yao Qiu, Ruishan Xin, Jianbin LuoAbstract:The mechanical property is an important index to evaluate the recovery degree of the Internal Crack zone. This work presents interfacial characteristics and Charpy impact properties of Crack healing zones in SA 508-3 steel, healing by hot compression and different healing treatment methods. When the holding time increased, the hardness of the matrix and Crack healing zone decreased. The hardness of the matrix was usually higher than the Crack healing zone, but the value of differences decreased with the increasing holding time. The percentage recovery of impact property increased when the holding time increased from 0 to 10 h. After holding for more than 10 h, the impact property decreased due to the mixed crystal structure. With the same total holding time, the recovery rate of Crack healing slowed down with the increment of heating times. The results show that for specimens with Internal Cracks, the method of healing at 950 °C and holding for 10 h was enough for Crack healing without sacrificing impact property.
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Effect of Parameters on Internal Crack Healing in 30Cr2Ni4MoV Steel for 600-Ton Ultra-Super Ingots
Metals, 2017Co-Authors: Ruishan Xin, Jianbin LuoAbstract:The effect of parameters on Internal Crack healing in 30Cr2Ni4MoV steel for 600-ton ultra-super ingots was systematically investigated. The results show that the degree of Crack healing increases with increasing healing temperature, holding time, reduction ratio, and hot pressure, and with decreasing strain rate. Internal Crack healing in 30Cr2Ni4MoV steel should be conducted at less than 1200 °C to avoid grain coarsening. Hot pressure, in the high-temperature elastic zone and perpendicular to the Crack faces, not only promotes the rapid Crack healing, but also prevents grain coarsening of the matrix.
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Restoration of impact properties of Internal Crack healing in a low carbon steel
Materials Science and Engineering: A, 2017Co-Authors: Ruishan Xin, Dongdong GuoAbstract:Abstract In this paper, a new model of Internal Crack presetting was presented via a butt-joint and compression method. Restoration of impact properties of Internal Crack healing in a low carbon steel was investigated using a 300 J pendulum impact testing machine. The results show that impact properties of Crack healing zone dramatically increase from 900 ℃ to 1000 ℃. Recrystallization in the Crack healing zone promotes the rapid restoration of impact properties of Internal Crack healing. Percentage recovery of impact properties after Crack healing treatment increases with increasing healing temperature and holding time in the temperature range 900–1100 ℃, while impact properties deteriorate at 1200 ℃ due to the formation of reticular ferrite and grain coarsening near the Crack healing zone. Additionally, a new phenomenon is discovered: when Internal Cracks are disappeared completely, tensile properties of Crack healing zones can be restored completely but their impact properties are only partially achieved. Post-fracture analysis indicates that in the initial healing stage the Charpy fracture exhibits massive brittle dimples and unhealed regions, and the ultimate fracture mode of the center region presents cleavage and ductile dimple mixed fracture.
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Effect of Heat Treatment on Microstructure and Hardness of Internal Crack Healing in a Low Carbon Steel
Key Engineering Materials, 2017Co-Authors: Ruishan Xin, Qing XianAbstract:The effect of heat treatment on microstructure and hardness of Internal Crack healing in a low carbon steel was studied. The Internal Cracks were produced into the samples by a drilling and compression method. The microstructure of Crack healing zone was examined using optical microscopy (OM) and scanning electron microscopy (SEM). The hardness of Crack healing zone was measured using a Vickers micro-hardness testing machine (FM-800). The results show that healing temperature plays a more significant role in Internal Crack healing than holding time. Compared as-quenched samples with as-normalized samples under the same healing parameters, it is found that cooling speed is also an important factor for Internal Crack healing. The migration and enrichment of iron atoms provide material source for recrystallization and grain growth of Crack healing zone. The existence of micro-voids leads to the hardness of the ferrite in the Crack healing zone lower than that in the matrix.
Jianbin Luo - One of the best experts on this subject based on the ideXlab platform.
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effect of deformation modes and heat treatment on microstructure and impact property restoration of Internal Crack healing in sa 508 steel
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2020Co-Authors: Yao Qiu, Ruishan Xin, Jianbin LuoAbstract:Abstract In this study, the effects of deformation modes and quenching and tempering (Q&T) process on the Crack healing and percentage recovery of impact properties were studied. The microstructure, Charpy impact properties and fracture surface morphology of the Crack zones at different healing stages were evaluated. When the healing temperatures was 950 °C and 1050 °C, percentage recovery of impact properties of the Internal Crack healing by multi-pass thermal deformation (twice upsetting and once drawing) was lower than that by uniaxial compression. After deformed by twice upsetting and once drawing at 1150 °C, the ‘Z type’ newly formed grain belt was observed in the Crack healing zone, which showed high resistance to the dynamic load. After Q&T process, the microstructure was evolved into the tempered bainite, and residual austenite decomposed gradually to carbides, precipitating out mainly along the grain boundaries. After Q&T process, the impact toughness of the Crack healing zones were improved, but the percentage recovery decreased, it is because that in the Crack healing zone, the carbides aggregated in the line, which has a lower resistance to applied force than the matrix.
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effects of heat treatment method on microstructure and mechanical properties of Internal Crack healing in sa 508 3 steel
2020Co-Authors: Yao Qiu, Ruishan Xin, Jianbin LuoAbstract:The mechanical property is an important index to evaluate the recovery degree of the Internal Crack zone. This work presents interfacial characteristics and Charpy impact properties of Crack healing zones in SA 508-3 steel, healing by hot compression and different healing treatment methods. When the holding time increased, the hardness of the matrix and Crack healing zone decreased. The hardness of the matrix was usually higher than the Crack healing zone, but the value of differences decreased with the increasing holding time. The percentage recovery of impact property increased when the holding time increased from 0 to 10 h. After holding for more than 10 h, the impact property decreased due to the mixed crystal structure. With the same total holding time, the recovery rate of Crack healing slowed down with the increment of heating times. The results show that for specimens with Internal Cracks, the method of healing at 950 °C and holding for 10 h was enough for Crack healing without sacrificing impact property.
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Effect of Parameters on Internal Crack Healing in 30Cr2Ni4MoV Steel for 600-Ton Ultra-Super Ingots
Metals, 2017Co-Authors: Ruishan Xin, Jianbin LuoAbstract:The effect of parameters on Internal Crack healing in 30Cr2Ni4MoV steel for 600-ton ultra-super ingots was systematically investigated. The results show that the degree of Crack healing increases with increasing healing temperature, holding time, reduction ratio, and hot pressure, and with decreasing strain rate. Internal Crack healing in 30Cr2Ni4MoV steel should be conducted at less than 1200 °C to avoid grain coarsening. Hot pressure, in the high-temperature elastic zone and perpendicular to the Crack faces, not only promotes the rapid Crack healing, but also prevents grain coarsening of the matrix.
Z G Wang - One of the best experts on this subject based on the ideXlab platform.
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effect of microstructure on ultra high cycle fatigue behavior of ti 6al 4v
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: Z G WangAbstract:The fatigue behavior of Ti-6Al-4V alloy with the bimodal and basketweave microstructures has been investigated. The results show that the S-N curves of Ti-6Al-4V with both microstructures continuously decrease with increasing the number of cycles to failure and have no horizontal asymptote in the regime of 10(5) to 10(9) cycles. SEM observation of fracture surface indicates that the Crack initiation sites abruptly shift from surface to interior of the specimen with decreasing the stress amplitude. It is found that the surface Crack initiation mainly results from the machining traces. Nevertheless, most of the Internal fatigue Cracks initiate in the border region of primary alpha-grains in bimodal microstructure or at alpha-beta interfaces in basketweave microstructure, which induced by inhomogeneity of microstructures and incompatibility of deformation between two phases. The size of the Internal Crack initiation site was evaluated and the dependence of the fatigue life on the location and size of the initiation sites is discussed. (C) 2007 Elsevier B.V. All rights reserved.
Oscar R Batic - One of the best experts on this subject based on the ideXlab platform.
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mechanical behavior of concretes damaged by alkali silica reaction
Cement and Concrete Research, 2008Co-Authors: Graciela Marta Giaccio, Raul Luis Zerbino, Jose Manuel Ponce, Oscar R BaticAbstract:Abstract Alkali-silica reaction (ASR) can induce the premature distress and loss in serviceability of concrete structures. The Internal Crack pattern produced by ASR affects both transport and mechanical properties. Usually linear expansions are considered as indicative of the grade of damage into the material (Internal Crack pattern), nevertheless as diverse types of ASR have been recognized (rapid or slow reactive aggregates, fine or coarse aggregates) the effects on strength and rheological properties could be different for a same expansion. This paper compares the mechanical response of a reference concrete (without reactive aggregates) and concretes prepared with three different types of reactive aggregates, with the same mixture proportions. The first concrete incorporated 10% of a highly reactive siliceous orthoquartzite as a part of the coarse aggregate, the second included a highly reactive sand, and the third prepared with a slow reactive granitic migmatite as coarse aggregate. Concretes were moist cured at 38 °C. When linear expansions ranging between 0.11 and 0.18% took place, the stress strain behavior in compression and the load-displacement response in flexure were measured. The same tests were performed on reference concrete at different ages, between 75 and 745 days. Microscopic observations were performed on polished and thin sections in order to analyze concrete microstructure. It appears that the failure mechanism of concrete in compression is clearly affected by ASR, the shape of the stress–strain curves reflects the presence of Internal fissures, showing that the capability of controlling Crack propagation decreases. Differences in the Crack pattern are also reflected in the shape of the load-deflection curves in tension, damaged concretes show an increased non-linearity and a more gradual softening. However, it was found that the modifications in the mechanical properties cannot be directly associated with a level of expansion, as the behavior depends on the component materials and mechanisms involved in the reaction.
Youshi Hong - One of the best experts on this subject based on the ideXlab platform.
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the mechanism of Internal fatigue Crack initiation and early growth in a titanium alloy with lamellar and equiaxed microstructure
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2020Co-Authors: Xiangnan Pan, Alexander Nikitin, Andrey Shanyavskiy, Guian Qian, Thierry Palinluc, Youshi HongAbstract:Abstract Traditionally, equiaxed α grains rather than lamellar microstructure (LM) domains in titanium alloys are regarded as potential Internal Crack origins in high-cycle fatigue (HCF) and very-high-cycle fatigue (VHCF) regimes. Here, we found that the fatigue Crack is prone to initiate from a large LM domain in a titanium alloy with the composition of LM and equiaxed microstructure (EM) of fine α grains. Then, the mechanisms of Internal Crack initiation and early growth for the cases of HCF and VHCF under stress ratio R = −1, 0.1 and 0.5 were addressed and a mechanism chart was constructed to illustrate the Internal Cracking behavior, especially showing that the numerous cyclic pressing process dominates the related microstructure evolution with grain size refinement and nanograin formation underneath the fracture surfaces in the region of Crack initiation and early growth.
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further investigation on microstructure refinement of Internal Crack initiation region in vhcf regime of high strength steels
Frattura ed Integrità Strutturale, 2019Co-Authors: Yukun Chang, Xiangnan Pan, Liang Zheng, Youshi HongAbstract:The profile samples prepared by focused ion beam (FIB) in Crack initiation region (CIR) and fish-eye (FiE) region of failed specimens subjected to rotary bending (RB) and ultrasonic axial (UL) fatigue testing with various stress ratios (R) were observed by transmission electron microscopy (TEM) with selected area electron diffraction (SAD) detection for two high-strength steels. The grain size and the thickness of nanograin layer along the Crack growth path in CIR underneath fine-granular-area (FGA) were measured for the cases of R 0 and the FiE region outside CIR for either negative or positive stress ratio cases, which suggests that the formation of nanograin layer in the FGA region is due to the numerous cyclic pressing (NCP) process and the plastic deformation ahead of the Crack tip may cause certain extent of microstructure deformation but is insufficient to form nanograin layer on Crack surfaces.