材料期刊网

利用硬度测量和X射线衍射分析,研究了Mg-5％Zn合金的时效硬化过程.指出合金在165℃时效过程中出现两个硬度峰,反映合金内发生了相应的结构变化. 对淬火合金的X射线研究表明,Mg基体中出现平行于(0001)和{1010}面的片状Zn原子富集区.在165℃时效初期,过饱和固溶体合金中桥出细微的二维及三维的亚稳定过渡相β′_1及一维杆状过渡相β′_2.β′_2存在时间很短,β′_2继续生核成长.时效100h后,稳定沉淀相β开始析出,并与β′_2共存.在190℃的时效过程中只出现一个硬度峰,相应于合金中同时出现β′_2及β析出相.测定了β′_1和β′_2过渡相的结构参数及其与母相的取向关系. β′_2的热稳定性相当高,能在250℃长时间存在,说明Mn-Zn系统的时效合金有可能在较高温度下使用.

The age-hardening processes of a Mg-5wt%Zn alloy have been studied bymeans of hardness measurement and X-ray diffraction analysis. On aging of thisalloy at 165℃, two hardness peaks with corresponding structural changes in thealloy were noticed. X-ray investigation of this alloy in quenched state revealedthat plate-like zinc clusters parallel to (0001) and {1010} planes of the magne-sium matrix were formed. At the initial stage of 165℃ aging, two-and three-dimensional metastable transition phase β'_1 particles and one-dimensional transitionphase β'_2 rods were precipitated out from the super-saturated solid solution. β'_1 existedonly for very short periods, while B'_2 still grew after aging for a total period of100h. when an equilibrium phase β began to precipitate out. During aging at190℃, only one hardness peak appeared, corresponding to the concurrent pre-cipitation of β'_2 and β phases. The structural parameters of β'_1 and β'_2 and theirorientational relationships with the matrix have en determined. The thermal stability of β'_2 was found to be rather high at 250℃, implyingthe probable applicability of the aged Mg-Zn alloys at higher temperatures.