热锻对喷射成形+挤压7055铝合金组织和性能的影响

Effects of Forging on Microstructure and Properties of Spray Formed and Extruded 7055 Aluminum Alloy

利用喷射成形技术制备了7055高强铝合金,并对合金进行了热挤压和热挤压+热锻加工,然后进行T74过时效处理。借助拉伸性能测试,电化学工作站、金相显微镜(OM)、扫描电镜(SEM)、透射电镜(TEM)等手段研究了热锻对挤压合金显微组织和性能的影响。结果表明:挤压合金的抗拉强度达到642 MPa,屈服强度达到598 MPa,而锻造合金的抗拉强度和屈服强度却下降了,但延伸率、电导率和硬度有所上升,断口形貌均为韧性断裂;无论是挤压还是锻造合金,晶界析出相中的主要合金元素含量均较基体高,而锻造合金晶界析出相中Mg、Zn元素含量较挤压合金降低,Cu元素含量升高;挤压和锻造合金在过时效后晶内都均匀分布着GP区和η′析出相,晶界η析出相则是断续的点状分布,但锻造合金晶内析出相粗化,晶界析出相变多;锻造合金的耐蚀性比挤压合金有所提升。

High strength 7055 aluminum alloys were prepared by spray forming. The microstructures and properties of the alloy after forging and extrusion were investigated using tensile test, electrochemical workstation, OM, SEM and TEM. The results indicate that the ultimate tensile strength and the yield strength of the extruded alloy can reach 642 MPa and 598 MPa at room temperature, respectively. The tensile strength and yield strength of the forged alloy decrease, but the elongation, electrical conductivity and hardness increase, and the alloys all exhibit ductile fracture. The content of main alloying elements in the boundary precipitates is higher than that in the matrix; the content of Mg and Zn in the forged alloy is lower than that in the extruded alloy, but the content of Cu element increases. Under the T74 condition, the main precipitates are GP zones and η′ phase in the grain, and the distribution of precipitates at the grain boundary is interrupted. The precipitated phase at grain boundary of the forged alloy is more than that of the extruded alloy, but the precipitated phases inside the grain are coarsened. The corrosion resistance of the forged aluminum alloy is better than that of extruded aluminum alloy.