电弧增材制造7075铝合金的微观组织与力学性能

Microstructure and Mechanical Properties of 7075 Aluminum Alloy Prepared by Wire and Arc Additive Manufacturing

7xxx系铝合金电弧增材制造过程中因组织不均匀与元素偏析导致成形试样性能较低,针对这一问题,对电弧增材制造7075铝合金薄壁件进行固溶+人工时效热处理(T6态),对比研究了热处理前后微观组织与力学性能的变化。结果表明,7075铝合金沉积态试样中晶粒被网状共晶组织包围,Zn、Mg和Cu元素在晶界富集,产生元素偏析。经过T6态热处理后,大部分共晶组织溶解,元素分布的不均匀性得到明显改善。与沉积态试样相比,热处理后试样的抗拉强度与断后伸长率增加,抗拉强度从(279.4±5.3)MPa提高至(493.9±10.2)MPa,断后伸长率从3.78%±0.35%增加到9.66%±1.70%。T6态试样的拉伸断口表面密布着韧窝,断裂方式为韧性断裂。

The mechanical properties of the 7xxx series aluminum alloy deposited specimens are low due to the uneven microstructure and element segregation in the process of wire and arc additive manufacturing(WAAM).In order to solve this problem,the 7075 aluminum alloy thin-walled specimens deposited by WAAM were subjected to solid solution+artificial aging heat treatment(T6 state).The microstructure evolution and mechanical properties before and after heat treatment were investigated.The results showed that the grains in the as-deposited specimen were surrounded by eutectics with network-like structure,and the elements of Zn,Mg and Cu were concentrated at the grain boundaries,resulting in the element segregation.After T6 heat treatment,most of the eutectics were dissolved.Moreover,the unevenness of the element distribution was significantly reduced.Compared with the as-deposited specimens,the tensile strength and elongation of T6 specimens were improved.The value of tensile strength increased from(279.4±5.3)MPa to(493.9±10.2)MPa,and the elongation increased from 3.78%±0.35%to 9.66%±1.70%.The tensile fracture surface of T6 specimen was densely covered with dimples.Therefore,the fracture mode was ductile fracture.