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研究了T6处理工艺(T6工艺430℃,6 h+215℃,2 h,空冷)对触变成形Mg2Sip/AM60B复合材料组织及力学性能的影响。结果表明:分布于晶间及晶内的硬脆β-Mg17Al12相在T4处理工艺:(T4工艺430℃×6 h,水冷)后几乎全部溶解,由此引起的β相割裂作用的基本消失,固溶强化作用及成分均匀化等导致抗拉强度和伸长率明显提高,而硬度显著降低;T6处理后,非连续析出β相在晶界及Mg2Si/α-Mg界面处呈现细小弥散分布,引起较强的晶界钉扎作用,导致抗拉强度和硬度显著提高,而伸长率略微降低,此状态下未发现明显的连续析出β相。最佳的T6处理工艺为(430℃,6 h+215℃,2 h),且抗拉强度和伸长率达到290 MPa和14.37%,相比触变态复合材料分别提高40.10%和83.06%。复合材料的断裂方式由触变态的沿晶断裂依次转变为T4态的混合断裂和T6态的穿晶断裂。
The effects of T6 treatment (T6, 430 ℃, 6 h, 215 ℃, 2 h, air cooling) on the microstructure and mechanical properties of thixoformed Mg2Sip / AM60B composites were studied. The results show that the hard and brittle β-Mg17Al12 phase distributed in the intergranular and intragranular phases almost completely dissolves in the T4 treatment process (T4 process 430 ℃ × 6 h, water cooling), and the β phase splitting action basically disappeared, The results show that the tensile strength and elongation increase obviously while the hardness decrease obviously due to solid solution strengthening and composition homogenization. After T6 treatment, the non-continuous precipitated β phase presents small and diffuse distribution in the grain boundary and Mg2Si / α-Mg interface Strong grain boundary pinning effect, resulting in significantly increased tensile strength and hardness, while the elongation decreased slightly, in this state found no significant continuous precipitation β phase. The best T6 treatment process was (430 ℃, 6 h +215 ℃, 2 h), and the tensile strength and elongation reached 290 MPa and 14.37%, respectively, which were increased by 40.10% and 83.06% respectively compared with the thixotropic composites. The fracture modes of composites change from the intergranular fracture of the thixotropic state to the mixed fracture of the T4 state and the transgranular fracture of the T6 state in turn.