球磨Mg-Ni非晶形成的局部熔化-相互扩散-快速凝固机理

The Local Melt-interdiffusion-rapid Solidification Mechanism of the As-milled Mg-Ni Amorphous Formation

采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、能谱分析仪等研究了Mg-Ni样品在球磨过程中的相结构、形貌、微区成分等变化规律,提出了球磨Mg-Ni非晶形成的局部熔化-相互扩散-快速凝固机理:样品在高于一定转速的球磨过程中发生局部熔化,镍粉镶嵌入熔体中,在磨球的撞击作用下,熔体经快速凝固形成成分不均的晶体样品。再次被磨球碰撞时,样品产生局部熔化-相互扩散-快速凝固过程并在界面处形成非晶薄层,随着球磨时间的延长,非晶层的厚度不断增加、样品的微区成分逐渐趋于均匀,原子排列也从长程有序转变为短程有序甚至无序的非晶结构。

The transformation mechanism of the structural, microstructure and composition of the Mg-Ni specimens during the ball milling were investigated by means of the X-ray diffraction, scanning electron microscope and energy spectrum analysis; and the local melt-interdiffusion-rapid solidification mechanism of the as-milled Mg-Ni amorphous formation was put forward as the following: part of the specimen could be melted and nickel would be studded into the melted sample, and the crystal structure which its composition is asymmetrical could be obtained after rapid solidification by impact of balls. The amorphous film on the interface of the sample would be formed during the process of local melt-interdiffusion-rapid solidification by means of ball collision and the thickness would increase with the ball milling time, thus, the composition trend towards uniformity and the atom rank become out-of-order to form amorphous.