中文摘要：

以A356铸造铝合金为研究对象,考察了该合金在真空吸注下的凝固组织、热处理组织及力学性能。结果表明,真空吸注使得凝固组织由常规条件下的粗大树枝晶转变为细小等轴晶,共晶硅由粗大杆状或针状转变为长度约为2~7μm的板片状;T6热处理后,常规铸造与真空吸注组织内的共晶硅均发生粒化和球化过程,但真空吸注条件下共晶硅尺寸更为细小,在-αAl基体上分布更加均匀,两种组织的析出相Mg2Si形状相似,均呈长度约400 nm的棒条状。随真空吸注的进行,拉伸试样的断裂形式由常规条件下的脆性断裂转变为脆性断裂与韧性断裂并存的混合模式,其抗拉强度、屈服强度、硬度和伸长率分别提高了12.5%、8.9%、87.3%和19.8%。

英文摘要：

Taking A356 aluminum alloy as research object,the as-solidified structure after vacuum suction casting,the heat-treated structure and the mechanical property have been studied.Subjected to vacuum suction casting,the as-cast structure changes from coarse dendrites obtained by conventional casting to fine equiaxed grains,while the coarse plate or needle-like eutectic silicon is substituted by some flake like ones with length as 2~7 μm.Independent of solidification path,granulized and sphericalized eutectic silicon is resulted after T6 heat treatment,but the size and the distribution of eutectic silicon in α-Al matrix become smaller and more homogeneous respectively,provided vacuum suction casting is performed.In the meanwhile,after heat-treatment,stick-shaped Mg2Si particle,with length as about 400 nm,is precipitated from both solidified structures.As compared to the conventional casting,the vacuum suction casting makes the fracture mode of tensile specimen change from brittle fracture to mixed mode of brittle and ductile fracture,so the tensile-strength,yield-strength,hardness,and elongation are increased by 12.5%,8.9%,87.3%,and 19.8%,respectively.