半固态等温热处理对原位Mg_(2)Si/AZ91复合材料组织及性能的影响  

Effect of Semi-Solid Isothermal Heat Treatment on the Microstructure and Performance of In-Situ Mg_(2)Si/AZ91 Composites

作　　者：赵奇强 高义民[1,2] 杨莎莎 肖鹏 ZHAO Qiqiang;GAO Yimin;YANG Shasha;XIAO Peng(State Key Laboratory for Mechanical Behavior of Material,Xi’an Jiaotong University,Xi’an 710049,China;Institute of Foundry Technology and Wear Resistant Materials,Xi’an Jiaotong University,Xi’an 710049,China)

机构地区：[1]西安交通大学金属材料强度国家重点实验室,西安710049 [2]西安交通大学铸造及耐磨材料研究所,西安710049

出　　处：《西安交通大学学报》2022年第10期190-200,共11页Journal of Xi'an Jiaotong University

基　　金：中国博士后科学基金资助项目(2021M692518);陕西省自然科学基础研究计划资助项目(2022JQ-331);国家重点研发计划资助项目(2021YFB3701204)。

摘　　要：为解决高体积分数Mg_(2)Si增强镁基复合材料中初生Mg_(2)Si相尺寸粗大导致的复合材料力学性能不佳的问题,提出了等温热处理细化Mg_(2)Si形貌的方法。研究了等温热处理对体积分数为10%的Mg_(2)Si/AZ91复合材料中Mg_(2)Si形貌、基体组织及硬度的影响规律,并揭示其演化机理。结果表明:在等温热处理过程中,初生Mg_(2)Si相曲率较小处优先溶解,导致初生Mg_(2)Si相在枝晶壁处熔断形成独立的颗粒,随后转变为具有最低表面能的球状,随着保温时间的延长,发生合并长大。对复合材料进行不同参数的等温热处理后发现,在510℃保温60min后,初生Mg_(2)Si相的细化效果最好,颗粒尺寸达到30.6μm,较原始试样减小了58.6%。在热处理过程中,α-Mg枝晶与沿晶界分布的Mg_(17)Al_(12)相发生成分均匀化,α-Mg晶界圆整化并且晶粒尺寸减小;复合材料硬度在等温热处理后显著降低,但随着初生Mg_(2)Si相和的α-Mg晶粒的细化,硬度有所回升,其硬度变化的主要机制是固溶强化、硬质相消失、细晶强化的共同作用。该研究为Mg_(2)Si/AZ91复合材料形貌改善以及性能提升提供了实验基础和理论依据。An isothermal heat treatment method is proposed to refine Mg_(2)Si size,so as to solve the problem of poor mechanical properties caused by coarse size of primary Mg_(2)Si phase in Mg matrix composites reinforced with high volume fraction Mg_(2)Si.In this paper,the effects of semi-solid isothermal heat treatment on the morphology of Mg_(2)Si,matrix microstructure and hardness of Mg_(2)Si/AZ91 composites with 10%volume fraction are studied,and its evolution mechanism is revealed.The results show that the primary Mg_(2)Si phase with low curvature dissolves preferentially during the isothermal heat treatment process,resulting in the fusing and forming independent particles at the dendrite wall,and then transforms into spherules with the lowest surface energy.With the extension of holding time,the primary Mg_(2)Si phase grows by merging.After[HJ]isothermal treatment with different parameters,the primary Mg_(2)Si phase has the best refinement effect with a particle size of 30.6μm after being kept at 510℃for 60 min,reduced by 58.6%.During the heat treatment,α-Mg dendrite homogenizes with Mg_(17)Al_(12) phase distributed along grain boundary,andα-Mg grains are spheroidizing and the grains size decreases.At the same time,it is found that the hardness of the composite decreases obviously after the isothermal heat treatment,but increases with the refinement of the primary Mg_(2)Si and theα-Mg grains.The hardness change is ascribed to the interaction of solution strengthening,hard phase disappearing and grain refinement strengthening.This paper provides experimental and theoretical basis for improving the morphology and properties of Mg_(2)Si/AZ91 composites.

关 键 词：Mg_(2)Si/AZ91复合材料 半固态等温热处理 组织演变 硬度 

分 类 号：TB333[一般工业技术—材料科学与工程]