喷射成形AlSiCuMg合金的热变形组织演变及再结晶行为

Microstructure Evolution and Recrystallization Behavior During Hot Deformation of Spray Formed AlSiCuMg Alloy

采用热压缩实验、SEM、TEM以及EBSD技术研究了喷射成形Al25Si4Cu1Mg(质量分数,%)合金的热变形组织演变规律及动态再结晶形核机制。结果表明:喷射态组织主要由等轴α-Al相、粗大块状Si相、AlSiCuMg相和不同尺度的Al_(2)Cu相构成。在623~723 K和0.001~5 s^(-1)条件下,细小的Al_(2)Cu相随形变温度的升高而逐渐回溶。高应变速率(5 s^(-1))热压缩时,位错塞积在粗大不溶初生相前沿产生应力集中,导致部分脆性初生相开裂,同时在初生相与α-Al相界面处出现局部裂纹。α-Al相则发生了完全动态再结晶。再结晶晶粒尺寸随着变形温度的下降和应变速率的提高而降低,晶粒内部的残留位错和形变亚结构随形变温度的升高而逐渐减少。随机织构表明,喷射成形Al25Si4Cu1Mg合金的动态再结晶机制为“粒子激发形核(PSN)”机制。

Wrought Al-Si alloy has partially replaced the traditional wear-resistant alloy for structural weight reduction owing to the excellent comprehensive properties,such as wear resistance,low coefficient of thermal expansion,and high specific strength.The deformation aluminum alloy based on Al-Si bi-nary alloy is widely used in aerospace and automotive industries.The hot compression test,SEM,TEM,and EBSD technologies were used to investigate the microstructure evolution and dynamic recrystallization nucleation mechanism of spray formed Al25Si4Cu1Mg(mass fraction,%)alloy.The results show that the as-sprayed microstructure consists of equiaxedα-Al,coarse Si phase,AlSiCuMg phase,and Al_(2)Cu phase with different scales.Under 623-723 K and 0.001-5 s^(−1),the fine Al_(2)Cu phases gradually dissolve with the increase in deformation temperature.During high strain rate(5 s^(−1))compression,dislocation accumulation causes a high degree of stress concentration in front of the coarse and insoluble primary phases,resulting in the cracking of some brittle primary phases.Local cracks also appear at the interfaces betweenα-Al and primary phases.Theα-Al phase undergoes complete dynamic recrystallization.The recrystallized grain size decreases with the increase and decrease in strain rate and deformation temperature,respectively.The residual dislocation and deformation substructure in the grain decrease with the increase in deformation temperature.The random texture demonstrates that the dynamic recrystallization mechanism of spray formed Al25Si4Cu1Mg alloy is“particle stimulated nucleation(PSN)”.