纯镁渗锌处理表面合金化机制研究

A Study on the Mechanism of Surface Zn-alloying for Pure Magnesium

摘要:

对纯镁进行了表面渗锌处理，研究了扩渗温度及扩渗时间对于合金化渗层组织、相结构及反应层连续性的影响。结果表明：扩渗温度的选择有一个合适的范围，温度过低，扩渗速度太慢甚至Zn元素原子的能量达不到其激活能，不能产生活性原子，扩渗过程无法进行。温度过高虽然有利于形成合金化渗层，但会使基体晶粒粗化，甚至改变整个基体，而且，温度过高不利于反应层（金属间化合物区）的稳定：扩渗时间的延长会促使Zn的进入量和金属间化合物的生成量增加，并削弱晶界扩散优势的影响，最终使固溶层和反应层趋于均匀化。要形成连续的反应层，扩渗温度应控制在400℃～420℃，相应的扩渗时间为8h以上。

Abstract:

Surface Zn-alloying modification was used to treat pure magnesium,and the effect of diffusion temperature and time on the alloyed microstructure,phase structure and the continuity of alloyed layers was studied as well.The results show that there is a reasonable range of the diffusion temperature to form the continual intermetallic compound layer.On the condition that the diffusion temperature is too low,the diffusion rate is also rather slow because there is no activated Zn atoms generated.Conversely,although high diffusion temperature is beneficial for the formation of alloyed layers,the base metal granular may become coarse then,even the whole base may get changed.Furthermore,excessively high temperature is harmful to the stability of the reacted layers(intermetallic compound).The prolongation of diffusion time may accelerate the flow of Zn atoms and therefore the formation of intermetallic compound,and weaken the preponderance of grain boundary,resulting in the uniformity of solution area and reacted area.In order to obtain the continual reacted area,the diffusion temperature has to be controlled within 400 420 and the corresponding diffusion time has to be over 8 h.