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采用约束棒模具热裂评价法,研究了Zn、Mg、Cu对7075铝合金热裂性能和组织的影响。结果表明,单一调节Zn时,热裂倾向系数(HCS)先减小,然后增大,达到最大值后减小。Zn含量为5.44%时,HCS最小,为76.8,Zn含量为6.44%时,HCS最大,为141.6。单一调节Mg时,HCS随Mg含量的增加而逐渐减小,Mg含量为1.68%时,HCS为最大,107.2;Mg含量为3.68%时,HCS最小,为72。单一调节Cu时,HCS先增大然后减小,Cu含量为1.80%时,HCS最小,为72;Cu含量为1.50%时,HCS最大,为101。7075约束棒的断裂方式为沿晶断裂,合金中不含共晶组织时,抗热裂性好;共晶组织较多,但又不足以明显补缩时,抗热裂性最差;共晶组织沿晶界大量分布,有利于补缩,热裂倾向小。7075铝合金约束棒试样铸态组织主要由树枝状α-Al相和η-MgZn2相组成。
The influence of Zn, Mg and Cu on the hot cracking properties and microstructure of 7075 aluminum alloy was studied by the thermal cracking method of constraining rod mold. The results show that when a single regulation of Zn, the thermal cracking tendency coefficient (HCS) decreases first, then increases, reaches the maximum and then decreases. When Zn content was 5.44%, HCS was the smallest, 76.8, and Zn content was 6.44%, HCS was the largest, which was 141.6. The HCS decreases with the increase of Mg content when Mg is monolithically adjusted. When the content of Mg is 1.68%, HCS is the largest, 107.2% and the content of Mg is 3.68%. The HCS firstly increases and then decreases when Cu is monolithically adjusted. When the Cu content is 1.80%, the HCS is the smallest and is 72. When the Cu content is 1.50%, the maximum HCS is 101.7075. The fracture mode of the constrained rod is intergranular fracture, When the alloy does not contain eutectic structure, the thermal cracking resistance is good; the eutectic structure is more, but not enough for obvious shrinkage, the thermal cracking resistance is the worst; the eutectic structure is distributed along the grain boundaries in a large amount, , Hot cracking tendency is small. The as-cast microstructure of the 7075 aluminum alloy constrained rod specimen mainly consists of dendritic α-Al phase and η-MgZn2 phase.