热处理对低Cu含量铸造Al-Si-Mg-Cu合金组织性能影响

Effects of Heat Treatment on Microstructure and Properties of Cast Al-Si-Mg-Cu Alloy with Low Cu Content

采用低Cu含量铸造Al-Si-Mg-Cu合金,通过光学显微镜、SEM和拉伸试验等方法,研究了热处理工艺对其组织性能的影响。结果表明,随着固溶时间增长,合金的强度及伸长率呈先增高后下降趋势,此时合金中共晶Si形貌会随着固溶时间而逐渐趋于球化。随着150℃下时效时间的延长,合金的强度逐渐升高,在时效14 h后抗拉强度达到339.87 MPa,而伸长率呈先下降后升高最后下降的趋势。在165℃下随着时效时间的延长,合金的强度先升高后下降,在10~14 h达到峰值,伸长率则持续降低。合金在热处理后析出W-Al_(2)Cu_(5)Si_(4)Mg_(4)及Mg_(2)Si相,两相弥散分布于基体中,形成第二相强化和弥散强化,提高合金的强度,但降低塑韧性。

The effects of heat treatment on microstructure and properties of cast Al-Si-Mg-Cu alloy with low Cu content were investigated by means of optical microscope,SEM and tensile test.The results indicate that the strength and elongation of alloy are increased firstly and then decreased with the extension of solution time,and the eutectic silicon morphology tends to spheroidized.With the extension of aging time at 150℃,the strength of alloy is gradually increased,and tensile strength reaches 339.87 MPa after aging for 14 h,while elongation presents a trend of decreasing first,and then increasing finally decreasing.At 165℃,the strength is increased firstly and then decreased with the aging time,which reaches a peak value at 10~14 h,while the elongation is decreased continuously.After heat treatment,W-Al_(2)Cu_(5)Si_(4)Mg_(4)and Mg_(2)Si phases are precipitated,which are dispersed in the matrix,leading to the second phase strengthening and dispersion strengthening,which can improve the strength of alloy and reduce the plasticity toughness.