AA6061铝合金铸坯平面压缩本构模型及组织演变

Constitutive model and microstructure evolution of AA6061 aluminum alloy casting blank in plain compression

利用Gleeble-3500热力模拟实验机研究AA6061铝合金铸坯平面压缩变形行为,分析其流变应力和组织演变规律。结果表明:平面压缩过程中流变应力随着变形温度的升高和应变速率的减小而逐渐降低;低温和低应变速率下(573 K/0.01 s-1),随着应变量增大,达到峰值应力后应力软化程度较大。同时,建立了描述AA6061铝合金铸坯平面压缩变形行为的双曲正弦型本构关系模型。大变形区的晶粒呈扁长的板条状,其晶界处有大量的第2相析出,晶粒的长径比随温度升高而减小,随应变速率增大而增大,小变形区晶粒组织形貌主要为椭圆形等轴状晶;高温下(723 K),部分第2相溶入晶粒内部,热变形组织演变机理主要为动态回复。

The plain compression deformation behaviors of AA6061 aluminum alloy casting blank were studied by Gleeble-3500 thermal simulator, and the rheological stress and microstructure evolution were analyzed. The results show that the rheological stress decreases with the increasing of deformation temperature and the decreasing of strain rate during the plain compression process, and at a low temperature and low strain rate(573 K/0.01 s-1), with the increasing of strain, the stress softening degree becomes larger after reaching the peak stress. At the same time, the hyperbolic-sine type constitutive model is developed to describe the plain compression deformation behaviors of AA6061 aluminum alloy casting blank. Therefore, the grains in the large deformation areas are characterized by the elongated lath-shape, and the second phases are precipitated in the grain boundaries. Furthermore, the length-diameter ratio of grain decreases with the increasing of temperature and increases with the increasing of strain rate, the microstructures in the small deformation areas are described by oval equiaxial grains, and the second phase dissolves into the grain at the higher temperature(723 K). Thus, the mechanism of the microstructure evolution in thermal deformation is mainly dynamic recovery.