离心铸造Cu-Cr-Zr-Mg合金中纳米铬相形成过程的研究

Research on Formation Process of Nano-chromium Phase in Centrifugal Casting Cu-Cr-Zr-Mg Alloy

利用真空熔炼+离心铸造技术制备出了凝固组织中含大量2.5~5 nm颗粒状和间距为0.6~1.2 nm条纹状的单质铬相的Cu-0.43Cr-0.22Zr-0.092Mg(wt%)合金。针对纳米级单质铬相形成原因不清楚的问题,借助SEM、XRD、TEM和HRTEM(高分辨率透射电镜)对合金的铸态显微组织进行观察分析,计算了铬相临界晶核半径,研究了单质铬相形核与生长过程。结果表明,Cu-0.43Cr-0.22Zr-0.092Mg(wt%)合金熔体在离心力作用下首先产生铬的偏聚,为铬相形核创造了条件。铬相形核后,在离心力作用下,铬相晶核向贫铬区域移动过程中略有长大,进入贫铬区域后长大基本停止,最后得到几个纳米尺寸的单质铬相。

A Cu-0.43Cr-0.22Zr-0.092Mg(wt%)alloy which has a large amount of elemental chromium phases with 2.5-5 nm particles and 0.6-1.2 nm spacing striped shape in the solidified structure was prepared by vacuum melting+centrifugal casting technology.Aiming at the problem that the reason for the formation of nano-scale elemental chromium phase is not clear,the as-cast microstructure of the alloy was observed and analyzed by means of SEM,XRD,TEM and HRTEM(high-resolution TEM),the critical crystal nucleus radius of chromium phase was calculated,and the nucleation and growth process of elemental chromium phase was studied.The results show that under the centrifugal force,the Cu-0.43Cr-0.22Zr-0.092Mg(wt%)alloy melt first produces chromium segregation,which creates conditions for chromium phase nucleation.After the chromium phase nucleation,under the action of centrifugal force,the chromium phase crystal nucleus grows slightly when moving to the chromium-poor region,and basically stops growing after entering the chromium-poor region,and finally several nano-sized elemental chromium phases are obtained.