Ni对CoFe合金相稳定性的影响

The Effect of Ni on Phase Stability of CoFe Alloy

摘要: 本工作利用第一性原理的热力学计算方法，研究了等摩尔配比的CoFe和CoFeNi合金的有序无序转变。计算结果的朗道理论分析表明：1) CoFe和CoFeNi合金的基态均为B2相结构；2) CoFe合金的高温平衡相为BCC结构，当达到转变温度时，CoFe合金会发生B2到BCC结构的相转变，有序无序转变温度大致在1400 K，摩尔组态熵变为；3) 随着Ni的添加，合金体系的转变温度会降低，CoFeNi合金发生了非平衡转变，其高温平衡相为FCC结构，有序无序转变温度低于750 K，摩尔组态熵变为。计算结果与两种合金的有序无序转变实验结果相吻合。

Abstract: In this work, the order-disorder transition of CoFe and CoFeNi alloys with equimolar proportions are studied by using the first-principle thermodynamic calculation method. The calculated results of Landau’s theoretical analysis show that: 1) the ground states of CoFe and CoFeNi alloys are B2 phase structure; 2) the high temperature equilibrium phase of CoFe alloy is BCC, when it rises to transition temperature, the phase transition from B2 to BCC will occur in CoFe alloy, the or-der-disorder transition temperature is about 1400 K, and the molar configuration entropy is ; 3) And with the addition of Ni, the transition temperature of the alloy system will decrease, a non-equilibrium transformation occurs in CoFeNi alloy, the high temperature equilibrium phase of CoFeNi alloy is FCC, the order-disorder transition temperature is lower than 750 K, and the mo-lar configuration entropy is . The calculated results are in good agreement with the expe-rimental results of the order-disorder transition of the two alloys.