Thermodynamic and kinetic analysis of CrB_(2) and VB_(2) formation in molten Al−Cr−V−B alloy  

熔融Al−Cr−V−B合金中CrB_(2)和VB_(2)形成的热力学和动力学分析

作　　者：A.KHALIQ H.T.ALI M.YUSUF 

机构地区：[1]Department of Mechanical Engineering,College of Engineering,University of Ha’il,Kingdom of Saudi Arabia [2]School of Engineering,RMIT University,Melbourne,VIC 3000,Australia [3]Department of Mechanical Engineering,College of Engineering,Taif University,P.O.Box 11099,Taif 21944,Kingdom of Saudi Arabia [4]Department of Clinical Pharmacy,College of Pharmacy,Taif University,P.O.Box 11099,Taif 21944,Kingdom of Saudi Arabia

出　　处：《Transactions of Nonferrous Metals Society of China》2021年第10期3162-3176,共15页中国有色金属学报（英文版）

基　　金：Taif University Researchers Supporting Project(No.TURSP-2020/293);Taif University,Taif,Saudi Arabia.

摘　　要：Transition metal impurities such as chromium(Cr)and vanadium(V)in solution deteriorate electrical conductivity of smelter grade aluminium(Al).These impurities can be removed from solution via boron treatment in which borides form upon their in-situ reaction with boron(B)-bearing substances.However,Cr removal from smelter grade Al solution is not well understood.A disagreement related to chromium boride(CrB_(2))formation in molten Al in the presence of other transition metals(V,Ti,Zr,Fe)by adding Al−B master alloy has been reported in literatures.This study presents an effort to understand the mechanism of Cr removal from Al−0.50%Cr−0.50%V(mass fraction)alloy by adding Al−B(AlB_(12))master alloy at 1023 K in the Al alloy solution.Results indicate that Cr removal from molten Al−0.50%Cr−0.50%V alloy by forming stable borides cannot be achieved at 1023 K;whereas excess of B in the solution preferentially forms aluminium boride(AlB2)over CrB_(2) during boron treatment of molten Al.The underlying kinetics of V removal from molten Al−0.50%Cr−0.50%V alloy revealed that early reaction stage is controlled by[B]/[V]mass transfer through liquid phase and mass transfer coefficient(km)was measured to be 9.6×10^(−4) m/s.The later reaction stage was controlled by[B]/[V]diffusion through boride(VB_(2))ring.This study,therefore,advocates to investigate alternative ways to remove Cr from molten Al.熔体中的铬(Cr)、钒(V)等过渡金属杂质会降低冶炼级铝(Al)的电导率。这些杂质可与含硼(B)物质发生原位反应形成硼化物,因此可以通过硼处理除去熔体中的杂质。然而,对于冶炼级铝熔体的除铬尚不清楚。文献中关于在其他过渡金属(V,Ti,Zr,Fe)存在的条件下,往熔融铝中加入Al−B母合金时硼化铬(CrB_(2))的形成存在分歧。本研究在1023 K下往铝合金熔体中加入Al−B(AlB_(12))母合金,探讨Al−0.50%Cr−0.50%V(质量分数)合金除铬的机理。结果表明,在1023 K下,无法通过形成稳定的硼化物从熔融的Al−0.50%Cr−0.50%V合金中除铬。在熔融铝的硼处理过程中,熔体中过量的B优先形成硼化铝(AlB_(2)),而不是CrB_(2)。从熔融Al−0.50%Cr−0.50%V合金中除钒的动力学研究表明,初期反应阶段由[B]/[V]的液相传质控制,传质系数(km)为9.6×10^(-4) m/s;后期反应阶段受[B]/[V]通过硼化物(VB2)环的扩散控制。因此,建议研究从熔融铝中除铬的替代方法。

关 键 词：boron treatment AL CrB_(2) VB_(2) thermodynamics kinetics 

分 类 号：TF821[冶金工程—有色金属冶金]