Cu-10%Fe合金微观组织中的晶体生长

The Crystal Growth in the Microstructure of Cu-10%Fe Alloys

研究了快速凝固时Cu-10%Fe合金的晶体生长行为。重点讨论了富Fe枝晶形成初期的一些重要特征,也分析了富Cu基体、富Cu第二相、富Cu沉淀相和富Fe沉淀粒子的形成过程。当晶粒的当量直径小于1μm时,界面能是影响晶粒形貌的主要因素,富Fe晶粒在界面能的作用下晶粒的轮廓基本都呈球形。富Fe晶粒尺寸由5微米向10μm的长大过程是晶粒由六面体向树枝晶发展的关键阶段,晶粒当量直径约10μm时,富Fe晶粒已具有了枝晶的雏形,晶粒棱、角处的凸起将形成枝晶的一次分枝。在其一次分枝生长初期,分枝的侧面并不平直,而是向液相中呈圆弧形凸出。一次分枝的长度与其跟部直径之比是判断分枝跟部有、无缩颈出现的重要参数,当该比值大于3时,将会存在缩颈现象。缩颈现象是溶质富集对枝晶侧向生长的影响结果,溶质富集主要影响枝晶的侧向生长而对枝晶顶端的生长速度影响不大。

The crystal growth process of Cu-10wt%Fe alloys in rapid solidification process is studied.The paper is focused on discussing some important characteristics of rich-Fe dendrite in the early growth stage.The forming processes of rich-Cu base, rich- Cu secondary phase,rich-Cu precipitate phase and rich-Fe precipitate particles are also discussed.When the equivalent diameter of grain is smaller than 1 μm, the interface energy makes that the outline of rich-Fe grain assumes roundness.The growth process of rich-Fe grain from 5μm to 10μm is the critical transformation stage from a hexahedron grain to a dendrite,when the equivalent diameter of grain is about 10μm,the shape of rich-Fe grain has a rudiment of dendrite,the protuberance of grain will develop into the primary arm.In the early growth stage of the primary arms, its side face is not a plane,instead,the side face bulges into liquid with a arc.The ratio of the length and joint diameter of the primary arm is an important factor to estimate wether the necking of the primary arm exist or not.When the ratio is larger than 3,the necking will appear.The solute enrichment mainly effects the side growth of dendrite rather than the tip growth.