Al2O3-SiO2(sf)-AZ91D复合材料的蠕变微观组织和变形机理

第 23 卷第 5 期中国有色金属学报 2013 年 5 月 V ol.23 No.5 The Chinese Journal of Nonferrous Metals May2013 文章编号：1004-0609(2013)05-1241-07

Al2O3-SiO2(sf)/AZ91D 复合材料的蠕变微观组织和变形机理

田 君，石子琼，钟守炎，廖梓龙

(东莞理工学院 机械工程学院，东莞 523808)

摘 要：在温度为473~573 K、 外加应力为30~100MPa下，

对硅酸铝短纤维增强AZ91D镁基(Al2O3-SiO2(sf)/AZ91D) 复合材料及 AZ91D 镁合金进行拉伸蠕变实验。通过 SEM 和 TEM 检测方法对其蠕变微观组织变化和变形规律进 行研究。结果表明，当两种材料的真应力指数n=3时，蠕变速率受位错的黏滞性滑移控制；复合材料的门槛应力 增大、短纤维有效的承载和传载作用导致复合材料的蠕变抗力显著增大。短纤维表面上的 MgO 保护层增大了短 纤维的承载和传载作用；短纤维的存在阻碍了复合材料的蠕变变形，降低了蠕变变形速率，控制着整个蠕变变形 过程。

关键词：镁基复合材料；蠕变；载荷传递；微观组织

中图分类号：TB332 文献标志码：A

Microstructural evolution and deformation mechanism during

creep of Al2O3-SiO2(sf)/AZ91D composite

TIAN Jun, SHI Zi-qiong, ZHONG Shou-yan, LIAO Zi-long

(School of Mechanical Engineering, Dongguan University of Technology, Dongguan 523808, China)

Abstract:The tensile creep tests were conducted on Al2O3-SiO2(sf)/AZ91D composite and an unreinforced AZ91D matrix alloys in the temperature range of 473?573 K and stress range of 30?100 MPa. By scanning electron microscopy and transmission electron microscopy, the microstructural effects on the creep behavior of the two materials were discussed.

The results show at a true stress exponent of n=3 for the two materials, and creep rate is affected by the viscosity slip control of the dislocation. The creep resistance of the reinforced material is shown to be considerably improved compared with that of the matrix alloy. The creep strengthening arises mainly from the increase of threshold stress of the composite and the effective load transfer between plastic flow in the matrix and the fibers. The MgO protective layer on the surface of short fibers can increase carrying and transferring of loads of the short fibers. The presence of short fibers can hinder the creep deformation of the composite, reduce the creep deformation rate, and control the whole creep deformation process.

Key words: magnesium matrix composite?creep?load transfer? microstructure

镁合金具有低密度、高比强度、高比刚度和易回 收等优点，在航空、航天、汽车、计算机、电子、通 讯和家电等行业有广泛的应用 [1?3] 。然而，在温度高于 423 K 时镁合金的抗蠕变能力较弱，这极大地限制了 其高温应用 [4?8] 。 复合材料化已成为提高合金高温蠕变 性能的一种重要手段 [9?12] 。利用来源广泛且价格相对 低廉的硅酸铝短纤维与 AZ91D 镁合金通过挤压铸造 而得到的硅酸铝短纤维增强 AZ91D 镁基复合材料被 证实具有较好的综合力学性能 [13] 。迄今为止，国内外 研究者对镁基复合材料的高温蠕变性能的研究主要集 中在颗粒增强或长纤维增强的镁基复合材料上，对短 纤维增强镁基复合材料的高温蠕变研究较少 [14] 。与长

基金项目：广东省自然科学基金资助项目(10151170003000002)

收稿日期：2012-08-13；修订日期：2012-11-09

通信作者：田 君，副教授，博士；电话：136********；E-mail：841608534@https://www.wendangku.net/doc/1317952513.html,