The microstructure of an Al-4Cu-Mg alloy during isothermal heat treatment in the Strain Induced Melt Activation （SIMA） process was investigated and the kinetics of grain growth was analyzed, The grain growth during ...The microstructure of an Al-4Cu-Mg alloy during isothermal heat treatment in the Strain Induced Melt Activation （SIMA） process was investigated and the kinetics of grain growth was analyzed, The grain growth during isothermal heat treatment of the Al-4Cu-Mg alloy coincided with the Ostwald ripening theory. During isothermal heat treatment, both grain shape and the high volume fraction of solid phase have significant effects on grain growth. Therefore, a new grain growth model based on the Ostwald ripening theory was proposed taking into consideration the grain shape and the volume fraction of solid phase. By comparing the calculated results with the experimental results, it was confirmed that the present model could be applied to grain growth during isothermal heat treatment of the Al-4Cu-Mg alloy in the SIMA process.展开更多
The introduction of compressive residual stress is an effective way to reduce fretting fatigue and fretting wear between a spinal implant rod and its holding fixture. The objective of this paper is to demonstrate that...The introduction of compressive residual stress is an effective way to reduce fretting fatigue and fretting wear between a spinal implant rod and its holding fixture. The objective of this paper is to demonstrate that cavitation peening can introduce compressive residual stress into the surface of a spinal implant rod manufactured from medical grade titanium alloy Ti-6Al-4V, which has already been processed by glass shot peening. In order to apply the cavitation peening for the small rod, whose diameter is only 5.5 mm, the cavitating region was concentrated by increasing the ambient pressure. The depth profiles of the resulting residual stress were evaluated by X-ray diffraction following layer removal by electropolishing. The results show that cavitation peening creates compressive residual stress deeper into the rod, even though the stress value at the near surface is saturated due to initial processing using glass shot peening. The depth of the compressive residual stress continuously increases from 44 μm to 230 μm with an increase in the cavitation peening processing time. In addition, the full width at half maximum value of the X-ray diffraction profile, which is closely related to the micro-strain, decreases by up to 32% following the application of cavitation peening.展开更多
The objective of this study is to investigate the possibility of continuous extrusion forming (Conform process) and microstructural evolution the of Cu-Mg alloy. The results indicate that Conform process can break as-...The objective of this study is to investigate the possibility of continuous extrusion forming (Conform process) and microstructural evolution the of Cu-Mg alloy. The results indicate that Conform process can break as-cast grains and refine the structure, meanwhile. This process can improve the degree of the structure homogeneity. The TEM and EBSD techniques were used to investigate the morphology, grain size and misorientation of the samples at cavity entrance and cavity export. Refined structures after shear deformation include broken grains and subgrains formed by dislocation reconstruction. Due to the relatively high deformation temperature, dynamic recrystallization occurred during deformation. The subgrain rotation nucleation took place, and grain boundary migration resulted in grain growth. However, the coarse grains were refined by anneal twins.展开更多
The variety,inner quality and surface quality of low-alloy spring steel wire rod for domestic automobile is summarized in detail.And according to commercial low-alloy spring steel wire rod variety, product quality lev...The variety,inner quality and surface quality of low-alloy spring steel wire rod for domestic automobile is summarized in detail.And according to commercial low-alloy spring steel wire rod variety, product quality level and its actual application situation on automobile supplied by present industrially developed country metallurgy enterprises,it is pointed that the variety of low-alloy spring steel wire rod for domestic automobile can't satisfy the requirements of automobile industry development,compare with overseas advanced technology,product quality has the following gaps:the first is that steel purity is low,the control level of non-metallic inclusions is not steady,there is often large grain difficult deforming non-deformation inclusions existing,the control level of steel purity has big difference,the level of large steel factory is high,but its steady has a large gap compare with foreign advanced level,not to mention small steel factory which research and development powder is low.The second is surface complete decarburization can' t be avoided completely.The third is that surface defects are more.The fourth is that composition segregation and structure segregation are not steady,steel wire can't be drawn normally when the segregation is serious. In all,the segregation of 55SiCrA is superior to 60Si2MnA obviously.The industrialization of domestic high level low-alloy spring steel wire rod can't seek quick success and instant benefits,independent innovation perseveringly must be adopted,the success may be reached after master core technologies and adopt the science way of step by step.展开更多
By adopting the alloy wire of Ni 80 Cr 20 as the welding core and adding the alloy elements of B, Si, Mo and W into the outer plating covering, a new type of wear resistant overlay welding rod of Ni Cr B Si was develo...By adopting the alloy wire of Ni 80 Cr 20 as the welding core and adding the alloy elements of B, Si, Mo and W into the outer plating covering, a new type of wear resistant overlay welding rod of Ni Cr B Si was developed. This overlay welding rod has several properties such as low melting point and good fluidity. With low content of W and Mo, the wearability and crack resistance of the overlay welding rod can be increased, and the hardness can be increased to about HRC64. This kind of overlay rod has been applied to the overlay of wearable workpieces, such as the valves of high temperature, high pressure and the side plates of floor boarding brick die.展开更多
Present study focuses on the terminal penetration of tungsten heavy alloy(WHA) long rod penetrator impacted against armour steel at an impact velocity of 1600 m/s. The residual penetrator and armour steel target recov...Present study focuses on the terminal penetration of tungsten heavy alloy(WHA) long rod penetrator impacted against armour steel at an impact velocity of 1600 m/s. The residual penetrator and armour steel target recovered after the ballistic test have been characterized using optical microscope, scanning electron microscope(SEM) and electron probe micro analyzer(EPMA). Metallurgical changes in target steel and WHA remnant have been analysed. Large shear stresses and shear localization have resulted in local failure and formation of erosion products. Severe plastic deformation acts as precursor for formation of adiabatic shear band(ASB) induced cracks in target steel. Recovered WHA penetrator remnant also exhibits severe plastic deformation forming localized shear bands, ASB induced cracks and shock induced cracks.展开更多
基金financially supported by the Doctorate Creation Foundation of Northwestern Polytechnical University (No.200210)
文摘The microstructure of an Al-4Cu-Mg alloy during isothermal heat treatment in the Strain Induced Melt Activation （SIMA） process was investigated and the kinetics of grain growth was analyzed, The grain growth during isothermal heat treatment of the Al-4Cu-Mg alloy coincided with the Ostwald ripening theory. During isothermal heat treatment, both grain shape and the high volume fraction of solid phase have significant effects on grain growth. Therefore, a new grain growth model based on the Ostwald ripening theory was proposed taking into consideration the grain shape and the volume fraction of solid phase. By comparing the calculated results with the experimental results, it was confirmed that the present model could be applied to grain growth during isothermal heat treatment of the Al-4Cu-Mg alloy in the SIMA process.
文摘The introduction of compressive residual stress is an effective way to reduce fretting fatigue and fretting wear between a spinal implant rod and its holding fixture. The objective of this paper is to demonstrate that cavitation peening can introduce compressive residual stress into the surface of a spinal implant rod manufactured from medical grade titanium alloy Ti-6Al-4V, which has already been processed by glass shot peening. In order to apply the cavitation peening for the small rod, whose diameter is only 5.5 mm, the cavitating region was concentrated by increasing the ambient pressure. The depth profiles of the resulting residual stress were evaluated by X-ray diffraction following layer removal by electropolishing. The results show that cavitation peening creates compressive residual stress deeper into the rod, even though the stress value at the near surface is saturated due to initial processing using glass shot peening. The depth of the compressive residual stress continuously increases from 44 μm to 230 μm with an increase in the cavitation peening processing time. In addition, the full width at half maximum value of the X-ray diffraction profile, which is closely related to the micro-strain, decreases by up to 32% following the application of cavitation peening.
文摘The objective of this study is to investigate the possibility of continuous extrusion forming (Conform process) and microstructural evolution the of Cu-Mg alloy. The results indicate that Conform process can break as-cast grains and refine the structure, meanwhile. This process can improve the degree of the structure homogeneity. The TEM and EBSD techniques were used to investigate the morphology, grain size and misorientation of the samples at cavity entrance and cavity export. Refined structures after shear deformation include broken grains and subgrains formed by dislocation reconstruction. Due to the relatively high deformation temperature, dynamic recrystallization occurred during deformation. The subgrain rotation nucleation took place, and grain boundary migration resulted in grain growth. However, the coarse grains were refined by anneal twins.
文摘The variety,inner quality and surface quality of low-alloy spring steel wire rod for domestic automobile is summarized in detail.And according to commercial low-alloy spring steel wire rod variety, product quality level and its actual application situation on automobile supplied by present industrially developed country metallurgy enterprises,it is pointed that the variety of low-alloy spring steel wire rod for domestic automobile can't satisfy the requirements of automobile industry development,compare with overseas advanced technology,product quality has the following gaps:the first is that steel purity is low,the control level of non-metallic inclusions is not steady,there is often large grain difficult deforming non-deformation inclusions existing,the control level of steel purity has big difference,the level of large steel factory is high,but its steady has a large gap compare with foreign advanced level,not to mention small steel factory which research and development powder is low.The second is surface complete decarburization can' t be avoided completely.The third is that surface defects are more.The fourth is that composition segregation and structure segregation are not steady,steel wire can't be drawn normally when the segregation is serious. In all,the segregation of 55SiCrA is superior to 60Si2MnA obviously.The industrialization of domestic high level low-alloy spring steel wire rod can't seek quick success and instant benefits,independent innovation perseveringly must be adopted,the success may be reached after master core technologies and adopt the science way of step by step.
文摘By adopting the alloy wire of Ni 80 Cr 20 as the welding core and adding the alloy elements of B, Si, Mo and W into the outer plating covering, a new type of wear resistant overlay welding rod of Ni Cr B Si was developed. This overlay welding rod has several properties such as low melting point and good fluidity. With low content of W and Mo, the wearability and crack resistance of the overlay welding rod can be increased, and the hardness can be increased to about HRC64. This kind of overlay rod has been applied to the overlay of wearable workpieces, such as the valves of high temperature, high pressure and the side plates of floor boarding brick die.
基金Defence Research Development Organization(DRDO)for financial support to carry out this work at Defence Metallurgical Research Laboratory
文摘Present study focuses on the terminal penetration of tungsten heavy alloy(WHA) long rod penetrator impacted against armour steel at an impact velocity of 1600 m/s. The residual penetrator and armour steel target recovered after the ballistic test have been characterized using optical microscope, scanning electron microscope(SEM) and electron probe micro analyzer(EPMA). Metallurgical changes in target steel and WHA remnant have been analysed. Large shear stresses and shear localization have resulted in local failure and formation of erosion products. Severe plastic deformation acts as precursor for formation of adiabatic shear band(ASB) induced cracks in target steel. Recovered WHA penetrator remnant also exhibits severe plastic deformation forming localized shear bands, ASB induced cracks and shock induced cracks.
