微量Sb对Mg-2.7Nd-0.4Zn-0.5Zr合金组织和性能的影响

发布时间：2018-06-01 05:21

本文选题：Sb + Mg-2.7Nd-0.4Zn-0.5Zr合金　；参考：《哈尔滨理工大学》2015年硕士论文

【摘要】：耐热镁合金一般都是稀土含量较高的稀土镁合金，它们在汽车制造业、国防工业、航空、航天等领域有着广阔的应用前景。Mg-Nd-Zn-Zr镁合金是“Mg-RE-Zr系”铸造镁合金的一种。该合金是以钕为主要合金元素的高强耐热镁合金，，铸造性能良好，显微疏松倾向和壁厚敏感性低，室温和高温性能优异。目前对该系合金的研究主要集中在稀土元素（如Nd、Y、Ce、La等）、Zn以及挤压制备工艺等对该系合金组织和性能的影响；本文首次提出以高强度耐热镁合金Mg-2.7Nd-0.4Zn-0.5Zr为基础，通过添加Sb微合金化和新的热处理工艺，探究元素Sb对Mg-2.7Nd-0.4Zn-0.5Zr镁合金显微组织结构和力学性能的影响。本文通过X射线物相分析(XRD)、光学显微镜(OM)、扫描电子显微镜(SEM)、EDS能谱分析、透射电子显微镜(TEM)、硬度测试以及室温拉伸试验等分析手段，系统地研究了微量Sb的变化对Mg-2.7Nd-0.4Zn-0.5Zr-xSb合金组织和力学性能的影响，揭示了元素Sb对合金材料的强化机制。实验结果表明，在含Zr镁合金中加入微量的合金元素Sb，由于生成Mg3Sb2相，可以对Mg-2.7Nd-0.4Zn-0.5Zr-xSb合金产生以下影响：进一步显著细化铸态、固溶态、时效态合金材料的晶粒尺寸，抑制合金材料晶粒长大；改善了铸态合金离异共晶相Mg12Nd的形貌、大小和分布；明显提高铸态、固溶态、时效态合金材料的硬度、强度和塑性。在不同热处理状态下，随着合金元素Sb含量的增加，晶粒变得更加细小，硬度基本上呈现持续增加的趋势，强度和塑性先增加后减小；基本上所有性能均在0.08wt%Sb附近达到极大值，不同热处理状态下合金材料的最小平均晶粒尺寸分别为13.9um（铸态）、35.7um（固溶态）和37.1um（时效态），最高布氏硬度分别为67.7（铸态）、65.1（固溶态）和89.5（时效态），最大抗拉强度分别为184MPa（铸态）、198MPa（固溶态）和275MPa（时效态），最大屈服强度分别为117MPa（铸态）、112.7MPa（固溶态）和205.5MPa（时效态），最大断后伸长率分别为11.1%（铸态）、23.5%（固溶态）和9.1%（时效态），最大断面收缩率分别为11.2%（铸态）、20.1%（固溶态）和9.5%（时效态）。元素Sb对镁合金的强化效果主要是由于细晶强化机制引起的。元素Sb对合金材料断裂方式影响较小，合金材料的断裂方式分别主要为沿晶断裂（铸态）、穿晶准解理断裂（固溶态）和穿晶解理断裂（时效态）。综合本文试验结果，Mg-2.7Nd-0.4Zn-0.5Zr合金加入0.08wt%Sb为宜。
[Abstract]:Heat-resistant magnesium alloys are generally rare earth magnesium alloys with high rare earth content. They have broad application prospects in automobile manufacturing industry, national defense industry, aviation, aerospace and other fields. Mg-Nd-Zn-Zr magnesium alloy is one of the casting magnesium alloys of "Mg-RE-Zr series". The alloy is a high strength and heat resistant magnesium alloy with neodymium as the main alloy element. It has good casting properties, low susceptibility to microporosity and wall thickness, and excellent properties at room and high temperature. At present, the study of the alloy mainly focuses on the effect of rare earth elements (such as Ndndyyyyralum cerium La and so on) on the microstructure and properties of the alloy, which is based on the high strength and heat resistant magnesium alloy Mg-2.7Nd-0.4Zn-0.5Zr for the first time. The effect of SB on microstructure and mechanical properties of Mg-2.7Nd-0.4Zn-0.5Zr magnesium alloy was investigated by adding SB microalloying and new heat treatment process. In this paper, X-ray phase analysis (XRDX), optical microscope (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), hardness test and room temperature tensile test are used to analyze the structure of the alloy. The effect of the change of trace SB on the microstructure and mechanical properties of Mg-2.7Nd-0.4Zn-0.5Zr-xSb alloy was systematically studied, and the strengthening mechanism of the element SB on the alloy material was revealed. The experimental results show that the addition of trace alloy element SB to Zr-containing magnesium alloy can have the following effects on Mg-2.7Nd-0.4Zn-0.5Zr-xSb alloy due to the formation of Mg3Sb2 phase: further, the grain size of as-cast, solid solution and aged alloy materials can be significantly refined. The morphology, size and distribution of Mg12Nd were improved, and the hardness, strength and plasticity of as-cast, solid solution and aged alloy materials were obviously increased. Under different heat treatment conditions, with the increase of SB content, the grain size becomes smaller and the hardness increases continuously, the strength and plasticity increase first and then decrease, and almost all the properties reach the maximum near 0.08wt%Sb. The minimum average grain sizes of alloy materials under different heat treatment conditions are 13.9um (as cast) and 37.1um (aged), respectively. The highest Brinell hardness is 67.7 (as cast, 65.1 (solid solution) and 89.5 (aged), respectively, and the maximum tensile strength is respectively. The maximum yield strength is 117MPa (as-cast 112.7MPa (solid solution) and 205.5MPa (aged 205.5 MPa), respectively. The maximum elongation after break is 11.1mm (solid solution) and 9.1 (aging), respectively. It is 11.2U (as cast) and 9.5A (aged). The strengthening effect of element SB on magnesium alloy is mainly caused by fine grain strengthening mechanism. Element SB has little effect on the fracture mode of alloy materials. The fracture modes of alloy materials are mainly intergranular fracture (as cast), transgranular quasi-cleavage fracture (solid solution state) and transgranular cleavage fracture (aging state). The results show that Mg-2.7Nd-0.4Zn-0.5Zr alloy is suitable for adding 0.08wt%Sb.
【学位授予单位】：哈尔滨理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG146.22

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