三元体系γ'相和θ相沉淀早期计算机研究

Computer Simulation of the Initial Precipitation Processes of γ' and θ Phases

基于三元合金沉淀动力学相场方程的微观离散格点形式建立模型,首次对Ni75Al11V14合金的γ'和θ2个有序相析出的早期过程进行了模拟,并计算了γ'有序相的成分序参数和长程序参数。结果表明Ni75Al11V14合金中γ'相的沉淀机制为非经典形核长大兼有失稳分解特征,先形成非化学计量比有序相,然后才形成化学计量比有序相;非化学计量比θ有序相在γ'相界处形成,距离γ'相界越远,其有序程度越低,θ有序畴存在2种类型水平分布和垂直分布,和它所依附的γ'相界面取向有关。

A kinetic model for ternary systems was developed based on the microscopic diffusion form of the phase-field equations describing the precipitation process in binary alloys. The model was used for atomic simulation of the initial precipitation mechanisms of γ' and θ ordered phases in Ni75Al11V14 and calculation of the order parameters of γ' (Ni3Al) phase. The results show: the γ' ordered phase precipitated from the disordered matrix by a nonclassical nucleation mechanism accompanied by spinodal decomposition, and an initially formed nonstoichiometric ordered phase later transformed into the stoichiometric one; Clusters of V atoms appeared at the γ' phase boundary resdulting in the formation of a nonstoichiometric θ ordered phase, The degree of ordering of the O domain decreases with distance from the γ'-phase boundary. There exists two type DO22 ordered domains: horizontal and vertical, depending on their adjacent γ' phase boundary.