强烈塑性变形诱导纯铁表面原位合金化

Situ alloying of iron surface induced by severe plastic deformation

以纯铁为基体,在表面机械研磨处理(SMAT)过程中加镍粉,处理不同时间后表面形成铁镍合金层。利用OM、XRD、SEM和EDS分析表面合金化层的微观结构、物相组成及元素分布情况。实验结果表明,SMAT处理80、300 min后,纯铁表层分别形成厚度为～50μm和50～100μm的合金层。SMAT过程中剧烈塑性变形诱导表面形成合金层主要包括粉体嵌入、焊合、粉末和基体细化、扩散。合金层的形成主要与强烈塑性变形作用下,表层晶粒细化导致扩散距离缩短及扩散通道(空位和位错等)增多有关。另外SMAT后纳米晶界具有高的应变能和非平衡状态也会促进元素的扩散,局部升温同样也可以促进元素的扩散。

Based on pure iron,by adding nickel powders during the process of surface mechanical attrition treatment(SMAT),iron-nickel alloy layer were formed after different treat times. The microstructure,composed phase and elemental distribution of surface alloyed layer were investigated by means of optical microscope(OM),X-ray diffraction(XRD),scanning electron microscopy(SEM) and energy disperse spectroscopy(EDS). Experimental results show that thickness is ～ 50 μm and 50 ～ 100 μm alloy layer produced respectively after treating for 80 and 300 min. The process of the alloy layer formation induced by the surface grain refinement can be classified as follows: implanting,seaming,refining and diffusion. The mechanism is mainly due to the grain refinement,which result in shortening the diffusion distance and increasing the diffusion channels such as vacancies and dislocations. In addition,nanocrystalline boundaries with high strain energy and non-equilibrium state will promote the diffusion of elements,local temperature rise may also facilitate the diffusion of elements.