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研究热处理工艺对铸态Mg-4.2Zn-1.5RE-0.7Zr镁合金显微组织和力学性能的影响。结果表明:铸态Mg 4.2Zn 1.5RE 0.7Zr镁合金的显微组织主要由α-Mg、T相和Mg51Zn20相组成;单级等温时效(325°C,10 h)以及双级时效(325°C,4 h)+(175°C,14 h)处理均未能使T相和Mg51Zn20相溶入基体,且晶粒也未明显长大。在325°C下时效10 h,晶内析出大量短杆状β′1相,延长时效时间将导致β′1相粗化及数量减少。Mg-4.2Zn-1.5RE-0.7Zr镁合金在325°C下时效10 h后具有最高的屈服强度(153.9 MPa)和抗拉强度(247.0 MPa),相比铸态合金分别增加48 MPa和23 MPa,伸长率降低至15.6%。Mg-4.2Zn-1.5RE-0.7Zr合金经双级时效(325°C,4 h)+(175°C,14 h)处理后的屈服强度和抗拉强度与单级等温时效处理(325°C,10 h)的相当,但伸长率有所下降。此外,不同状态下Mg-Zn-RE-Zr镁合金的断裂主要表现为准解理断裂,但局部特征有差别。
The effect of heat treatment on the microstructure and mechanical properties of as-cast Mg-4.2Zn-1.5RE-0.7Zr magnesium alloy was studied. The results show that the microstructure of as-cast Mg 4.2Zn 1.5RE 0.7Zr magnesium alloy is mainly composed of α-Mg, T phase and Mg51Zn20 phases. Single-stage isothermal aging (325 ° C, 10 h) and two-stage aging C, 4 h) + (175 ° C, 14 h) failed to make T phase and Mg51Zn20 phase into the matrix, and the grain did not significantly grow. After aging at 325 ° C for 10 h, a large amount of short rod-like β’1 phase precipitated in the grains, and prolonging the aging time resulted in the coarsening of the β’1 phase and the decrease of the number of β’1 phases. Mg-4.2Zn-1.5RE-0.7Zr magnesium alloy has the highest yield strength (153.9 MPa) and tensile strength (247.0 MPa) after aging at 325 ° C for 10 h, up to 48 MPa and 23 MPa, elongation decreased to 15.6%. The yield strength and tensile strength of the Mg-4.2Zn-1.5RE-0.7Zr alloy treated with two-stage aging (325 ° C, 4 h) + (175 ° C, 14 h) C, 10 h), but the elongation decreased. In addition, the fracture of Mg-Zn-RE-Zr magnesium alloy under different states mainly shows quasi-cleavage fracture, but the local features are different.