挤压—剪切变形镁合金的摩擦磨损行为及机理研究

发布时间：2018-01-13 22:17

  本文关键词：挤压—剪切变形镁合金的摩擦磨损行为及机理研究　出处：《重庆理工大学》2015年硕士论文　论文类型：学位论文

  更多相关文章： 挤压-剪切 显微组织 变形镁合金 磨损机制 有限元分析

【摘要】：镁合金挤压-剪切工艺(Extrusion-Shear,简称ES)是课题组开发的一种结合了正挤压和等径角挤压的新型塑性变形技术。研究表明该工艺能够有效细化镁合金晶粒,提高镁合金力学性能,但对镁合金摩擦磨损性能的影响尚未研究。本文在研究ES变形镁合金微观组织和力学性能的基础上,通过往复摩擦试验,结合数值模拟对ES变形镁合金的摩擦磨损性能进行了深入研究。对不同塑性变形方式(挤压-剪切、正挤压)、不同ES变形温度和模具转角及不同坯料原始状态下制备的变形镁合金进行了XRD、金相组织观察和显微硬度测试实验及分析。结果表明:与正挤压相比,挤压-剪切变形中模具转角的两次剪切作用使AZ系镁合金微观组织更细化均匀;变形温度为370℃时,ES变形AZ31镁合金晶粒细小,变形温度为400℃和420℃时,晶粒有所长大,组织不均匀;模具转角为120°时ES挤压制备的AZ61镁合金微观组织比模具转角为135°时细小均匀。不同塑性变形参数下AZ系镁合金的显微硬度差异大不,但显微硬度值较高,达到了60HV左右。对比研究了不同塑性变形方式(挤压-剪切、正挤压)和变形温度下制备的AZ31镁合金,不同模具转角及不同原始坯料状态下制备的ES变形AZ61镁合金的往复滑动摩擦磨损行为,根据摩擦系数和磨损率变化探索了挤压-剪切工艺参数对AZ系镁合金摩擦磨损性能的影响,结合磨损表面和磨屑的SEM和EDS实验,分析了不同摩擦工况下的磨损机制。结果表明:ES变形比正挤压制备的镁合金耐磨性较好;ES变形温度为370℃,模具转角120°下制备的AZ系镁合金磨损性较好;坯料均匀化与未均匀化制备的ES变形镁合金耐磨性接近。磨损机制随法向载荷和往复频率的增加由轻微磨损的粘着磨损、磨粒磨损和氧化磨损转变为严重磨损的剥层磨损、塑性变形和熔融磨损。采用DEFORM-3D有限元软件对挤压-剪切和正挤压AZ31镁合金和不同往复频率下ES变形AZ31镁合金的摩擦磨损过程,及加载初期材料受力情况进行了数值模拟。应力应变场的分布和变化表明:相同摩擦条件下ES变形镁合金和正挤压镁合金相比产生的塑性变形程度较小,耐磨性相对较好;有效应力应变往复随频率增加而减小,随外加载荷增加而增大,累积应力应变可诱发塑性变形和剥层磨损的发生,增大金属表面磨损程度。
[Abstract]:Extrusion-Shear Extrusion-Shear process of magnesium Alloy Extrusion-Shear. ESU is a new plastic deformation technology which combines forward extrusion and equal angular extrusion. The research shows that this process can refine magnesium alloy grain effectively and improve the mechanical properties of magnesium alloy. However, the effect on the friction and wear properties of magnesium alloys has not been studied. Based on the study of microstructure and mechanical properties of es wrought magnesium alloys, the reciprocating friction test is carried out in this paper. The friction and wear properties of es wrought magnesium alloy were studied by numerical simulation. The XRD, metallographic observation, microhardness test and analysis of wrought magnesium alloy prepared under different es deformation temperature, die rotation angle and different blank raw state were carried out. The results showed that the results were compared with that of positive extrusion. The microstructures of AZ series magnesium alloys are more fine and uniform due to the double shearing of die rotation angle in extrusion-shear deformation. When the deformation temperature is 370 鈩，

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