DOC《细晶Mg-Al-Ti-C中间合金的制备及其对AZ91D组织和性能的影响》

细晶Mg-Al-Ti-C中间合金的制备及其对AZ91D组织和性能的影响 孟宏杰1,董天顺2,叶校瑛1,刘利2,王拓2 (1.

唐山工业职业技术学院 机械工程系,河北 唐山 063299;

2.河北工业大学 材料科学与工程学院,天津 300130) 摘要:采用两步法+铜模喷铸的方式制备具有颗粒增强和细晶强化作用的Mg-Al-Ti-C中间合金,并研究了其对AZ91D组织和性能的影响.通过OM、SEM、XRD、硬度及拉伸试验对中间合金和AZ91D的组织形貌和力学性能进行分析.结果表明,两步法制备得到了Mg-Al-Ti-C中间合金,经过铜模喷铸后,TiC颗粒尺寸大幅度减小,且弥散分布于Mg-Al-Ti-C中间合金中;

用该细晶Mg-Al-Ti-C中间合金处理AZ91D,后者的抗拉强度提高了19.8%,硬度提高了64.9%;

TiC颗粒既有颗粒增强作用,也能作为AZ91D凝固时的异质形核核心,起到细晶强化作用. 关键词:两步法;

铜模喷铸;

Mg-Al-Ti-C中间合金;

AZ91D合金 中图分类号:TG146.2 文献标志码:A 文章编号:1007-7545(2019)02-0000-00 Preparation of Fine-grained Mg-Al-Ti-C Master Alloy and Its Effect on Microstructure and Properties of AZ91D Alloy MENG Hong-jie1, DONG Tian-shun2, YE Xiao-ying1, LIU Li2, WANG Tuo2 (1. Department of Mechanical Engineering, Tangshan Polytechnic College, Tangshan 063299, Hebei, China;

2. School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130, China) Abstract:Mg-Al-Ti-C master alloy with particle reinforcement and fine crystal strengthening was prepared by two-step method and copper mold inject casting. Effects of Mg-Al-Ti-C master alloy on microstructure and properties of AZ91D were investigated by means of OM, SEM, XRD, hardness test and tensile test. The results show that Mg-Al-Ti-C master alloy was produced by two-step method, and TiC particles are dispersedly distributed in Mg-Al-Ti-C master alloy with their sizes becoming much smaller. After treatment with Mg-Al-Ti-C master alloy, tensile strength and hardness of AZ91D rise by 19.8% and 64.9% respectively. Besides particle reinforcing effect, TiC particles can also be used as heterogeneous core of AZ91D to strengthen substrate. Key words:two-step method;

copper mold inject casting;

Mg-Al-Ti-C master alloy;

AZ91D alloy 镁合金比强度高、铸造性能和减震性能好,广泛应用于电子、汽车、航空航天等领域[1].但镁合金为密排六方晶体结构,在室温下可动滑移系少,塑韧性较差,容易开裂.提升镁合金力学性能的方式有很多,最常用的是颗粒增强和细化处理[2-5].当采用外加颗粒增强时,若颗粒较细,由于表面能较大,则团聚倾向严重,因此难以达到理想的强化效果.而对镁合金进行细化、变质处理,改变α-Mg和β-Mg17Al12相的形态和尺寸,也是提高镁合金性能的常用方法.目前主要采用碳质孕育法(如添加CaCO

3、C2Cl6及纯碳粉等)或者使用内部晶粒较粗大的铝合金用中间合金对镁合金进行细化、变质处理,但是迄今为止镁合金尚没有商业化的晶粒细化剂,亟待开发[6].以中间合金的形式向镁合金中加入增强颗粒,如果加入的增强颗粒尺寸很小且分散度很高,并且与镁合金基体或其中的第二相存在共格关系,则有望在实现颗粒增强的同时达到细晶强化的效果,目前这方面的研究还鲜有报道.试验采用两步法制备了含有TiC颗粒的Mg-Al-Ti-C中间合金,并对其进行了铜模喷铸处理,研究了细晶Mg-Al-Ti-C中间合金对AZ91D组织和性能的影响和机理.