时效对Al-Zn-Mg-Mn-Zr-Cr-Y合金挤压材组织与性能的影响

Effect of aging treatment on microstructure and properties of Al-Zn-Mg-Mn-Zr-Cr-Y extruded alloys

采用硬度和拉伸力学性能测试以及TEM组织观察分析,研究了一种中强可焊Al-Zn-Mg-Mn-Zr-Cr-Y合金的时效制度与组织性能的关系。结果表明,该合金合适的单级时效温度为120℃,且随着时效时间的延长具有二次强化现象,出现峰值的时间分别在24 h和72 h。产生强化的主要原因为GP区的形成和η'相的析出。时效第一峰处合金有较好的综合力学性能,其抗拉强度、屈服强度和伸长率分别为445 N/mm^2、350 N/mm^2、15.3%。该合金最佳的双级时效制度为120℃6 h+145℃10 h,经其处理后的抗拉强度、屈服强度、伸长率分别为447 N/mm^2、359 N/mm^2、17.2%,双级时效使合金的伸长率有所提高。合金晶内析出相主要为η'强化相,晶界上出现不连续分布的平衡相和较窄的无析出带(PFZ)。

The effect of aging treatment on microstructure and properties of a weld-able moderate strength A1-Zn-Mg-Mn-Zr-Cr-Y extruded alloy is investigated with hardness test, tensile mechanical properties test and transmission electron microscope （TEM）. The result shows that the suitable one-step aging temperature of the alloy is 120℃. As aging time ex- tends, secondary reinforcement presents in the alloy,with the peak hardness emerging at 24 h and 72 h, respectively. The formation of G. P zones and the precipitation of η＇ phases are the main reasons that cause reinforcement. The excellent comprehensive mechanical properties are reached at the first peak of aging time. The tensile strength, yield strength and elongation are 445 N/ram2 ,350 N/mm2 and 15.3%, respectively. The optimum two-step aging treat- ments of the alloy are 120℃ 6 h ＋ 145℃ 10 h. The tensile strength,yield strength and elon- gation are 447 N/mm2 ,359 N/mm2 and 17.2% under this condition, respectively. The two- step aging treatment improves the alloy＇s elongation. The precipitation phases of grain interi- ors are η reinforced phases, and discontinued equilibrium phases and narrow Precipitation Free Zones （PFZ） appear on the grain boundaries.