(1. 华南理工大学 国家金属材料近净成形工程技术研究中心，广州 510640；
2. 华南理工大学 机械与汽车工程学院，广州 510640)
摘 要: 对AZ91镁合金铸板进行搅拌摩擦加工，研究热处理对被加工材料组织和力学性能的影响。结果表明，经413 ℃保温16 h固溶处理后，铸态合金晶界处粗大的网状β-Mg17Al12相基本溶入α-Mg基体中。在搅拌摩擦加工过程中，组织发生明显细化，产生细小的等轴状再结晶晶粒。预先固溶处理可使摩擦加工合金晶界处少量未溶β-Mg17Al12相全部溶入基体。随后时效处理导致β-Mg17Al12相以两种方式析出，时效初期以晶界处非连续析出为主，然后再发生晶粒内部的连续析出。时效处理可较大程度地提高合金的硬度，以16 h最为显著，搅拌区平均显微硬度的最大值为118.4HV。预先固溶处理可以提高搅拌摩擦加工合金的塑性，伸长率为31.5%；随后时效处理(16 h)则可以大幅度提高合金的抗拉强度，由搅拌摩擦加工板的265 MPa增至340 MPa。
关键字: AZ91镁合金；搅拌摩擦加工；组织；力学性能；热处理
（1. National Engineering Research Center of Near-net-shape Forming for Metallic Materials,
South China University of Technology, Guangzhou 510640, China;
2. School of Mechanical and Automotive Engineering, South China University of Technology,
Guangzhou 510640, China）
Abstract:AZ91 magnesium alloy sheet was subjected to friction stir processing (FSP), and the microstructure and mechanical properties of the experimental materials were investigated. The results show that coarse β-Mg17Al12 networks dissolve into the α-Mg matrix after solution treatment (ST) at 413 ℃ for 16 h. FSP results in the significant grain refinement and the generation of equiaxed recrystallized grains. Only a few β-Mg17Al12 phases are found at the grain boundaries in the FSP specimen, while these phases disappear in the pre-ST+FSP specimen. Two types of precipitates, i.e. discontinuous precipitation (DP) and continuous precipitation (CP), are found after aging treatment. The lamellar DPs are the dominant ones at the initial aging, and the CPs form within the grains. Aging treatment can improve the microhardness, with the maximum average value of 118.4HV (16 h). The pre-ST+FSP specimen shows excellent ductility with an elongation of 31.5%. Succedent aging treatment can remarkably improve the tensile strength of the alloy, which increases from 265 MPa in the FSP alloy to 340 MPa.
Key words: AZ91 magnesium alloy; friction stir processing; microstructure; mechanical property; heat treatment
