铸造A铝合金的拉伸性能及其断口分析.doc

铸造A356铝合金的拉伸性能及其断口分析 冉 广,周敬恩,王永芳 (西安交通大学金属材料强度国家重点实验室, 陕西西安710049) ? 摘要:研究了铸造A356-T6铝合金板不同位置处的拉伸性能?采用扫描电子显微镜和光学显微镜对拉伸断口及断口纵剖面的组织形貌进行了观察分析?试验结果表明,铸造A356一T6铝合金的拉伸屈服强度随离浇道口平面距离的增加而减小,断裂强度则是先减小然后再增大,而延伸率随高度变化不明显?铸造A356-T6铝合金的平均屈服强度?断裂强度?延伸率和断面收缩率分别为2l6.64 MPa,224 MPa,1.086%和0.194% ?断口分析表明拉伸断口的表面分布着杂质?孔洞?铸造缩孔和氧化膜等缺陷,断口表面也存在开裂的由碳?氧?铁?镁?铝和硅元素形成的复合粒子?铸造A356-T6铝合金在拉伸过程中,裂纹萌生于共晶硅粒子与基体结合处,并沿枝晶胞之间的共晶区域进行扩展,当前进的裂纹遇到取向不一致的共晶硅粒子时,裂纹将截断共晶硅粒子?铸造A356-T6铝合金拉伸断裂方式为沿胞(即穿晶)断裂的准解理断? 关键词: 铸造A356铝合金:A1-7%Si-0.4Mg; 拉伸性能; 断裂机制:断口形貌 中图法分类号:TG 146.2 l 文献标识码:A 文章编号:1002一l85X(2006)10一l620—05 Abstract:The cast A356 aluminum alloy plate produced by precision sand(chemical bonded)process was heat treated by T6 technology. Tensile properties in diferent locations of cast A356-T6 aluminum alloy plate were studied.The fractography and its longitudinal surface were examined and analyzed by optical microscope(OM),scanning electric microscope(SEM)and energy spectrum analysis(ESA).The results show that the yield strength of cast A356-T6 aluminum alloy decreases with increasing of the distance from the inner gate plane, but the tensile strength firstly decreases and then increases with increasing of the distance.The elongation variation with the distance is not obvious.The average values of yield strength(o-0 2),tensile strength(o-b),elongation( and reduction in area (%)of A356-T6 alloy are 2 1 6.64 M Pa,224 M Pa,1.086% and 0.1 94% ,respectively.The inclusions,pores,shrinkage porosities and oxide film were observed in fracture surface.And the fracture particle combined by C,O,Fe,M g,AI and Si elements was also observed in some tensile fracture surface.During the tensile testing,the cracks initiated from the interface between eutectic silicon and aluminum matrix,and propagated along eutectic region around the dendritic cel1.The tensile fracture m echanism of cast A356-T6 aluminum alloy is quasi-cleavage feature of trangranular model(along the cell fracture). Key words:cast A356 aluminum alloy;AI-7%