A356合金轮毂的微观组织及拉伸性能研究

Study on microstructure and tensile properties of A356 alloy wheel

研究了低压铸造A356合金轮毂重要部位微观组织及拉伸性能.结果表明:先凝固的部位微观结构细化,二次枝晶间距较小,后凝固的部位随着保温时间的延长,晶粒呈长大趋势,二次枝晶间距尺寸增大,因此最先凝固的内轮缘相较其他部位表现出最优的微观组织与力学性能;辐条处存在缩孔、缩松缺陷,在拉伸过程中,截面上缺陷的存在降低了承受外载荷的有效面积,试样在较小的载荷下发生断裂,因此辐条部位力学性能最差;在拉伸断口表面观察到较少的准解离平面和分布均匀的韧窝形貌,拉伸断裂方式为以韧性断裂为主的韧脆混合型断裂.

This paper studies the microstructure and tensile properties of important parts of low-pressure cast A356 alloy wheels.The results show that the microstructure of the first solidified part is refined,and the secondary dendrite spacing is small.With the extension of the holding time,the grains tend to grow and the secondary dendrite spacing increases.Compared with other parts,the solidified inner rim shows the best microstructure and mechanical properties.There are shrinkage holes and shrinkage defects at the spokes.During the stretching process,the existence of defects on the cross-section reduces the effective area to withstand external loads.The specimen breaks under a smaller load,so the spokes have the worst mechanical properties.A small quasi-dissociation plane and a uniformly distributed dimple morphology were observed on the fracture surface,so the fracture mode was a ductile-brittle mixed fracture mainly composed of ductile fracture.