通过显微维氏硬度计、电子背散射衍射和透射电子显微镜等分析手段研究了不同电流密度对单晶铜棒材电化学冷拉拔过程中拉拔力、硬度、晶体取向及位错的影响。结果表明,当电流密度为6.7 m A·cm^(-2)时,激活的滑移系数量最多,拉拔力最...通过显微维氏硬度计、电子背散射衍射和透射电子显微镜等分析手段研究了不同电流密度对单晶铜棒材电化学冷拉拔过程中拉拔力、硬度、晶体取向及位错的影响。结果表明,当电流密度为6.7 m A·cm^(-2)时,激活的滑移系数量最多,拉拔力最小,且拉拔后棒材的表面硬度也最小。不同的电流密度使单晶铜棒材的塑化程度不同,其主要原因是由于晶体内滑移系激活数量不同引起,导致位错易于运动,使得位错缠结减少。而在更高的电流密度下,由于表面腐蚀层厚度的增加,激活的滑移系数量减少,继而摩擦力增大,位错密度增大,使得拉拔力再次增大。展开更多
The effects of grain refining parameters on microstructure of AM60B magnesium alloy with MgCO3 were investigated and then a refining technique was developed.Simultaneously,the corresponding mechanisms were discussed.T...The effects of grain refining parameters on microstructure of AM60B magnesium alloy with MgCO3 were investigated and then a refining technique was developed.Simultaneously,the corresponding mechanisms were discussed.The results indicate that increasing addition temperature of MgCO3 or pouring temperature is beneficial for obtaining fine grains.There is an optimal addition amount of 1.2%at the addition temperature of 790°C.Prolonging holding time at 790°C will increase grain size.The grain refining technique that 1.2%MgCO3 is added at 790°C followed by holding for 10 min and pouring can decrease the grain size from 348μm of the un-refined alloy to 69μm.The nucleation substrates are actually the Al4C3 particles formed from reactions between the MgCO3 and alloying elements in the melt.Besides the heterogeneous nucleation regime,growth restriction of the Al4C3 particles agglomerated at growing front is the other mechanism.展开更多
The microstructures and crystal growth directions of permanent mould casting（PMC） and directionally solidified（DS） Al-Cu alloys with different contents of Cu were investigated. Simultaneously, the effects of pouri...The microstructures and crystal growth directions of permanent mould casting（PMC） and directionally solidified（DS） Al-Cu alloys with different contents of Cu were investigated. Simultaneously, the effects of pouring temperature on the microstructure and crystal growth direction of permanent mould casting pure Al were also discussed. The results indicate that the α（Al） crystals in the pure Al do not always keep common columnar grains, but change from the columnar grains to columnar dendrites with developed arms as the pouring temperature rises. The growth direction also varies with the change of pouring temperature. Cu element has similar effects on the microstructures of the PMC and DS casting Al-Cu alloys and the α（Al） crystals gradually change from columnar crystals in turn to columnar dendrites and developed equiaxed dendrites as the Cu content increases. The crystal growth direction in the PMC alloys gradually approaches （110） orientation with increasing Cu content. But the resulting crystals with growth direction of （110） do not belong to feathery grains. There are also no feathery grains to form in all of the DS Al-Cu alloys.展开更多
文摘通过显微维氏硬度计、电子背散射衍射和透射电子显微镜等分析手段研究了不同电流密度对单晶铜棒材电化学冷拉拔过程中拉拔力、硬度、晶体取向及位错的影响。结果表明,当电流密度为6.7 m A·cm^(-2)时,激活的滑移系数量最多,拉拔力最小,且拉拔后棒材的表面硬度也最小。不同的电流密度使单晶铜棒材的塑化程度不同,其主要原因是由于晶体内滑移系激活数量不同引起,导致位错易于运动,使得位错缠结减少。而在更高的电流密度下,由于表面腐蚀层厚度的增加,激活的滑移系数量减少,继而摩擦力增大,位错密度增大,使得拉拔力再次增大。
基金Project(G2010CB635106)supported by the National Basic Research Program of ChinaProject(NCET-10-0023) supported by the Program for New Century Excellent Talents in University of China
文摘The effects of grain refining parameters on microstructure of AM60B magnesium alloy with MgCO3 were investigated and then a refining technique was developed.Simultaneously,the corresponding mechanisms were discussed.The results indicate that increasing addition temperature of MgCO3 or pouring temperature is beneficial for obtaining fine grains.There is an optimal addition amount of 1.2%at the addition temperature of 790°C.Prolonging holding time at 790°C will increase grain size.The grain refining technique that 1.2%MgCO3 is added at 790°C followed by holding for 10 min and pouring can decrease the grain size from 348μm of the un-refined alloy to 69μm.The nucleation substrates are actually the Al4C3 particles formed from reactions between the MgCO3 and alloying elements in the melt.Besides the heterogeneous nucleation regime,growth restriction of the Al4C3 particles agglomerated at growing front is the other mechanism.
基金Project(51061010)supported by the National Natural Science Foundation of ChinaProject(NCET-10-0023)supported by the Program for New Century Excellent Talents in University of ChinaProject(J201103)supported by the Program for Hongliu Outstanding Talents of Lanzhou University of Technology,China
文摘The microstructures and crystal growth directions of permanent mould casting（PMC） and directionally solidified（DS） Al-Cu alloys with different contents of Cu were investigated. Simultaneously, the effects of pouring temperature on the microstructure and crystal growth direction of permanent mould casting pure Al were also discussed. The results indicate that the α（Al） crystals in the pure Al do not always keep common columnar grains, but change from the columnar grains to columnar dendrites with developed arms as the pouring temperature rises. The growth direction also varies with the change of pouring temperature. Cu element has similar effects on the microstructures of the PMC and DS casting Al-Cu alloys and the α（Al） crystals gradually change from columnar crystals in turn to columnar dendrites and developed equiaxed dendrites as the Cu content increases. The crystal growth direction in the PMC alloys gradually approaches （110） orientation with increasing Cu content. But the resulting crystals with growth direction of （110） do not belong to feathery grains. There are also no feathery grains to form in all of the DS Al-Cu alloys.
