汽车用6005A-T6铝合金动态力学性能研究

Dynamic Mechanical Property of 6005A-T6 Aluminum Alloy for Automotive Use

通过对6005A-T6铝合金进行准静态拉伸试验和动态拉伸试验,研究了应变速率对6005A-T6铝合金准静态和动态力学性能及断裂行为的影响。结果表明:6005A-T6铝合金的强度随着应变速率提高而增大,当拉伸应变速率达到200s^(-1)时,抗拉强度、屈服强度分别较准静态拉伸提高30MPa、25MPa,其中以准静态到应变速率10 s^(-1)的过程中,材料的抗拉强度、屈服强度上升最为明显;试样应变速率与流变应力的关系符合Johnson-Cook本构模型,其拟合得到的本构方程为σ=(220.56+298.85ε0.506)(1+0.0209lnε)。6005A-T6铝合金塑性随着应变速率的增大而逐渐增大,当应变速率达到200s^(-1)时塑性反而下降。在高速拉伸变形状态下,位错密度的增加和滑移带的增多是导致高速状态下强度及延伸率提高的主要原因;当应变速率达到200s^(-1)时由于拉伸速率过快,晶粒来不及进行大量变形是断后延伸率反而降低的主要原因。

The effects of strain rate on quasi-static and dynamic mechanical properties and fracture behavior of 6005 A-T6 aluminum alloy were studied by quasi-static tensile test and dynamic tensile test. The results show that the strength of 6005 A-T6 aluminum alloy increases with the increase of the strain rate. When the tensile strain rate reaches 200 s^(-1), the tensile strength and yield strength increase by 30 MPa and 25 MPa, respectively, compared with quasi-static tensile. In the process from the quasi-static to the strain rate of 10 s^(-1), the tensile strength and yield strength of the material increase most obviously. The relationship between strain rate and flow stress accords with Johnson-Cook constitutive model, and the constitutive equation obtained by fitting is as follows σ=(220.56+298.85ε0.506)(1+0.0209 lnε).The plasticity of 6005 A-T6 aluminum alloy increases with the increase of strain rate, but decreases when the strain rate reaches 200 s^(-1).Under the condition of high speed tension, the increase of dislocation density and the increase of slip band are the major reasons for the increase of strength and elongation. When the strain rate reaches 200 s^(-1), the main reason for the decrease of elongation after fracture is that the grain has no time for large deformation due to the too fast tensile rate.