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

AIM OS的研究是开发新的镁合金具有比适用于活塞和其他英语零件地下热载量的Hestint Hestant铝和镁合金的热量和腐蚀性更高的。研究了镁合金的衰老特征，热功能，corothion行为和微观控制C.构成重的稀土元素。镁将大的浓度转移到较低的浓度下，因此温度降低，降低的二进制或y二进制二进制或y的浓度。在250 2）所研究的降水序列允许如下：镁超级固体溶液 *beta *beta“（do_ <19>） *平衡β（nd Contentning合金：FCC，Y含有合金：BCC）。可稳定的beta“阶段”。结果是，在热滚动或热锻造和耳朵上，晶粒剂的固定会减少。通过均质素化合物到达溶解度极限和折叠的均质化合物。在耐铝合金的常规抗热合金中