初始晶粒尺寸对2024铝合金热变形行为和组织的影响

利用永磁搅拌近液相线铸造和普通铸造方法制备不同晶粒尺寸的2024铝合金铸锭,利用Gleeble-1500热模拟试验机研究初始晶粒尺寸对不同压缩变形条件下2024铝合金的热变形行为和变形后显微组织的影响。研究表明:2024铝合金的热变形行为依赖于变形条件和初始组织。初始晶粒尺寸对流变应力的影响是:当应变速率小于0.1 s~(-1)时,流变应力随晶粒尺寸减小而减少;当应变速率为10 s~(-1)时,流变应力随晶粒尺寸减小而增大。降低变形温度会弱化晶粒尺寸对流变应力的影响。热压缩流变应力随应变速率增大而增大,随变形温度升高而减小。应变速率为10 s~(-1)时,热压缩应力应变曲线呈现周期性波动;只在粗晶2024铝合金中发现变形剪切带。

Effects of initial grain size on hot deformation behavior and microstructure of 2024 aluminum alloy

Various grain sizes of 2024 aluminum alloy were made by permanent magnetic stirring-low superheat pouring and traditional casting. The effects of initial grain size on flow stress behavior and the deformation microstructure during hot compression deformation were studied by using Gleeble-1500 thermal simulation machine. The results show that the hot deformation behavior of Al material was sensitive to deformation condition and initial microstructure. The flow stress decreases as the initial grain size decreases when strain rate is lower than 0.1 s?1. This procedure is reversed at strain rate of 10 s?1. The influence of initial grain size on flow stress is less effective when deformation temperature decreases. The results also indicate that the flow stress and peak stress increase with increasing strain rate, and decrease with increasing deformation temperature in both fine and coarse grain aluminum. The flow stress curve shows the waveform character when the strain rate is 10 s?1. The shear bands are found only in coarse-grained 2024 aluminum alloy.