Phase Decomposition of Heat Resistant Magnesium Alloys Containing Heavy Rare Earth Elements and Its Control

含重稀土耐热镁合金的相分解及其控制

基本信息

批准号：
07455257
负责人：
KOJIMA Yo
金额：
$ 4.99万
依托单位：
Nagaoka University of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07455257/
关键词：
Magnesium Alloy Rare Earth Containing Alloy Phase Diagram Aging Characteristics Hot Workability Microstructural Control Corrosion Resistance High Temperature Tensile Property ミクロ組織

项目摘要

The aim of this study is to develop a new magnesium alloy which has more excellent heat and corrosion resistance than that of the conventional heat resistant aluminum and magnesium alloys that could be applicable to piston and other engine parts undergoing the highest thermal load among automobile parts. The Mg-rich portion of phase diagrams, aging characteristics, hot workability, corrosion behavior and microstructural control of magnesium alloys containing heavy rare earth elements were investigated. Finally, the alloys were hot-forged into a piston shape and their tensile properties were also evaluated. (1) The solid solubilities of heavy rare earth elements in magnesium shift largely to lower concentrations than those of Mg-Gd or -Dy binary alloys by Nd or Y addition with decreasing temperature. As a result, alloys containing Gd or Dy of more than 6% and Nd or Y of more than 3% show marked age hardening even at 250ﾟC and have higher tensile strength than the conventional magnesium … More alloys. (2) The precipitation sequences of the investigated alloys are as follows : Magnesium supersaturated solid solution* beta" (DO_<19>) *beta' (bco) *Equilibrium beta (Nd containing alloy : fcc, Y containing alloy : bcc). The remarkable age hardening is caused by the precipitation of metastable beta"-phase. The beta"-phase precipitate preferentially on the dislocations introduced by the hot rolling or hot forging and, therefore, precipitation free zone near the grain boundaries is reduced. As a result, tensile properties are enhanced by the hot working. (3) It is possible for the investigated alloys to suppress grain coarsening and to reduce the amount of remained eutectic compound by lowering the homogenizing temperature to just above the solubility limit and, therefore, to directly dieforge all specimens into a piston shape without an intermediate upset forging. Die-forged Mg-10%Gd-3%Y alloys exhibits a tensile strength of 290MPa and 0.2% proof stress of 250MPa at 250ﾟC,which are superior to those of the conventional heat resistant magnesium alloys and are more than double those of the conventional heat resistant aluminum alloys. (4) A fine Mg (OH)_2 layr is formed as the stable protective film on the surface of all investigated alloys by the additions of rare earth elements under a corrosive environment containing a chloric ion. Less

这项研究的目的是开发一种新的镁合金，该合金具有与常规耐热铝和镁合金相比，该合金具有更高的热量和耐腐蚀性，这些合金可能适用于活塞和其他发动机零件，在汽车部件中具有最高的热负载。研究了富含毫克的相图，老化特性，热功能性，腐蚀行为和含有重稀土元件的镁合金的微结构控制。最后，将合金热填充成活塞形，还评估了其拉伸性能。（1）镁移位中重稀土元件的固体溶解度在很大程度上比MG -GD或二元合金的浓度较低，而温度则降低。结果，包含超过6％和y的GD或DY的合金即使在250°C下也显示出明显的年龄硬化，并且比常规镁具有更高的拉伸强度……更多的合金。（2）所研究合金的沉淀序列如下：镁过饱和固体溶液 *beta“（do_ <19>） *beta'（bco） *平衡β（ND含有合金：FCC，Y contage Alloy：bcc）。显着的年龄是由稳定的Beta beta beta beta“ -phase”引起的。 β“ - 相位”在热滚或热锻造引入的位置上优先沉淀，因此，在晶粒边界附近附近的精确区域会降低精确区域。结果，热工作会增强拉伸性能。（3）可以使所研究的合金抑制粒度并降低较低的繁殖量，以使其在较低的范围内降低了较低的繁殖量，以使其降低造成量的繁殖量，而降低了较低的繁殖量，而降低了较低的型号，则可以降低造型的量，而降低了较低的型号，而降低了较低的繁殖量，则可以降低供应量，而降低了较低的繁殖量。直接将所有标本变成活塞形状，而没有中间的锻造锻造Mg（OH）_2 Layr通过在含有氯离子的腐蚀性环境中添加稀土元素，形成所有研究合金表面上的稳定膜。较少的