电弧增材制造2024铝合金的微观组织与力学性能

Microstructure and Mechanical Properties of 2024 Aluminum Alloy Prepared by Wire Arc Additive Manufacturing

采用电弧增材制造工艺制备了三元Al-Cu-Mg(2024)铝合金成形试样,并对试样的晶粒形貌、物相组成、元素分布与力学性能进行研究。结果表明,2024铝合金成形试样宏观上表现出层状特征,单一沉积层可以分为层间区域与层中区域2部分,晶粒形貌由层中区域的等轴晶转变为层间区域的柱状晶;成形试样微观组织主要包括α-Al、θ-Al_(2)Cu与S-Al_(2)CuMg相;由于增材制造非平衡凝固过程,成形试样出现元素偏析,层中区域Mg元素在Al基体中均匀分布;电弧重熔作用下,层间区域元素偏析严重,Cu元素以共晶组织的形式在晶界偏析,Mg元素出现局部富集;成形试样的平均抗拉强度、屈服强度与断后伸长率分别为(323.5±6.6)MPa、(178.7±6.2)MPa和(9.03±0.67)%,高于铸造退火态2024铝合金的力学性能;由于微观组织的不同,层中区域与层间区域出现不同的裂纹扩展行为,层间区域裂纹沿着共晶组织分布路径扩展,表现为沿晶断裂,层中区域裂纹扩展模式变为穿晶断裂。

Owing to its outstanding advantages,such as low specific gravity,high specific strength,and good machinability,2024 aluminum alloy has been used as various load components in the aerospace field and has become an important lightweight material.The properties of the 2024 aluminum alloy are highly correlated with its microstructures.Accordingly,in this study,2024 aluminum alloy deposited specimens were fabricated using wire arc additive manufacturing.Further,the microstructures and mechanical properties of the deposited specimens were investigated in different regions.The layered characteristics could be observed macroscopically in the deposited specimens,and a single deposition layer was divided into two regions:interlayer and innerlayer.The grain morphology changed from equiaxed grains in the innerlayer region to columnar grains in the interlayer region.The deposited specimens mainly includedα-Al,θ-Al_(2)Cu,and S-Al_(2)CuMg phases.In the nonequilibrium solidification process of additive manufacturing,the deposited specimens presented element segregation.The distribution of Mg in the Al matrix was uniform for the innerlayer region.However,Cu was segregated as eutectics at the grain boundary in the interlayer region.The average tensile strength,yield strength,and elongation of deposited specimens were(323.5±6.6)MPa,(178.7±6.2)MPa,and(9.03±0.67)%,respectively,which were higher than those of cast annealing 2024 aluminum alloy.Owing to the difference in the microstructure,the innerlayer and interlayer regions showed different crack propagation behavior.The cracks in the interlayer region propagated along the distribution path of eutectics,showing intergranular fracture,and the crack propagation mode in the innerlayer region changed to transgranular fracture.