压铸AZ91合金拉伸过程模拟与试验验证

Computer Simulation and Experimental Verification of the Tensile Process of Die Casting AZ91 Alloy

结合常温拉伸力学性能、金相组织和三维显微形貌重构结果对AZ91合金的拉伸过程进行了模拟,并与压铸AZ91合金试棒的拉伸力学性能进行了对比研究。结果表明,压铸AZ91合金拉伸断口横截面可见尺寸不等的显微气孔缺陷,且表面的缺陷数量较少,而心部的缺陷数量更多、尺寸更大;拉伸试棒中气孔的存在会在拉伸过程中产生应力集中,进而产生显微裂纹,并最终造成裂纹扩展和断裂;在相同尺寸和间距的缺陷参数下,平行于拉伸载荷方向的气孔相对垂直于拉伸载荷方向的气孔对AZ91合金力学性能的影响小,且在两侧尺寸较小的气孔位置不变前提下,中间气孔尺寸增大会使AZ91合金抗拉强度降低;有限元模拟的力学性能计算值与压铸AZ91合金实测值的误差小于5%,可以对含有内部缺陷的合金拉伸力学性能进行有效预测。

The uniaxial tensile process of AZ91 alloy was simulated by combining the tensile mechanical properties, microstructure and three-dimensional microstmcture reconstruction results at room temperature, and the tensile mechanical properties of die casting AZ91 alloy were compared and analyzed. The results show that the cross-section area near the tensile fracture surface of typical die cast AZ91 alloy shows different sizes of micro porosity defects, and the number of defects in the surface area is relatively small, while the number of defects in the core area is larger, and the size is bigger. The existence of stomata in tensile test rods will cause stress concentration during the tensile process, then produce micro cracks, and ultimately cause crack growth and fracture. Under the same defect parameters （size and spacing）, the distribution of pores in the direction of tension parallel to the direction of tensile load is less influenced by the mechanical properties of AZ91 alloy, and the tensile strength of AZ91 alloy will be reduced by the increase of the size of the middle hole. The error between the calculated values of mechanical properties and the measured values of the die cast AZgl alloy is within 5%, and the tensile properties of the die casting AZ91 alloy containing internal defects can be predicted effectively by using the finite element simulation method.