Ni_(75)Mn_xAl_(25-x)合金早期沉淀相的微观相场模拟

Microscopic phase-field simulation for formation of pre-precipitation phase in Ni_(75)Al_(25-x)Mn_x alloy

采用三元微观相场动力学模型研究Ni75MnxAl25-x合金早期沉淀相的形成过程。对合金微观组织演化图像、有序相体积分数曲线、序参数曲线及占位几率的分析表明:该合金首先析出L10结构,随后L10结构向L12结构转变,L12结构在L10结构的内部析出。随着Al浓度的增大,等成分有序化阶段缩短;且L10结构体积分数增大,发生结构转变的时间提前。Al和Mn原子在(001)和(002)面几乎同时有序排列,但是一定时间后(002)面原子开始贫化,发生结构转变,Al原子主要占据β位,Mn原子主要占据αⅡ位。合金最终析出单一的L12伪二元结构。

The microscopic phase-field model was used to simulate the formation of pre-precipitation phase in Ni75Al25-xMnx alloy.The results of the microscopic morphology evolution of alloys,the volume fraction curves,order parameter curves and occupation probability show that L10 phase precipitates from the Ni75Al25-xMnx alloy first and then transforms into L12 phase inside of L10 phase in the following time.With the increase of Al concentration,the nucleation incubation periods of L10 and L12 phases and structure transformation time obviously become shorter.The ordering of Al and Mn atoms takes place in（001） and（002） planes simultaneously.As followed,the atom order degree begins to decrease in（002） planes and the structure is changed.Al atoms preferentially occupy the β site and Mn atoms preferentially occupy the Ⅱ site.Finally,the L10 pseudobinary structure precipitates in the alloy system.