【摘要】 通过具有不同冷却速率的阶梯型金属型制备出Al-Si-Cu-Mg-Ni合金,并进行固溶时效处理(T6),利用光学显微镜、XRD和SEM分析研究铝合金不同状态下的显微组织和力学性能。结果表明,冷却速率越大,合金的二次枝晶臂间距越小,抗拉强度、屈服强度、硬度和伸长率越大;热处理能明显地提高合金的力学性能。经T6处理后,共晶Si尺寸变得均匀细小,且弥散分布在α-Al基体中。截面厚度为20mm的合金热处理后抗拉强度、屈服强度和硬度(HB)分别为367MPa、229MPa和125,相对于铸态的分别提高了49.2%、54.7%和34.3%。合金拉伸断口呈现出大量韧窝和一定数量解理平面的混合形貌,表现为混合断裂特征。更多还原

【Abstract】 The ladder-type Al-Si-Cu-Mg-Ni alloy samples were prepared by metal mold at different cooling rates and treated by T6heat treatment.The microstructure and mechanical properties of the Al alloys under different conditions were investigated by optical microscope(OM),X-ray diffractometer(XRD) and scanning electron microscope(SEM).The results indicate that the secondary dendrite arm spacing(SDAS)of alloy is decreased,and the tensile strength,yield strength,hardness and elongation are increased gradually with the cooling rate increase.Heat treatment can improve significantly the mechanical properties of the alloy.After T6treatment,the uniform and fine eutectic-Si is distributed dispersedly in theα-Al matrix.The tensile strength,yield strength and hardness of the alloy with 20mm in cross-section thickness after heat treatment reach 367 MPa,229 MPa and 125HB,about 49.2%,54.7% and 34.3% higher than those of the as-casted alloy,respectively.Tensile fracture of the alloy is characterized by a mixed morphology of a large number of dimples and a number of cleavage plane.更多还原