The atomic scale computer simulation for initial precipitation mechanism of Ni75Al6V19 alloy was carried out for the first time by employing the microscopic diffusion equation. The initial precipitation process was invest igated throughsimulating the atomic pictures and calculating the order parameters of the two kinds of ordered phases. Simulationresults show that the γ′ordered phase precipitated earlier than θ ordered phase by congruent ordering+spinodal decomposition mechanism and thus produced a nonstoicheometric γ′ single ordered phase. Then, the nonstoichiometricθ phase precipitated by a non-classical nucleation and growth mechanism at the APBS of γ′ phase.
Yuhong ZHAO Hua HOU Hong XU Yongxin WANG Zheng CHEN Xiaodong SUN
The coherent elastic strain-induced morphological transformation of a binary cubic model alloy was simulated with different strain energy parameters. The microscopic diffusion equation was combined with the theory of microscopic elasticity. The results show that when the strain energy is neglected, the randomly distributed equiaxed particles are obtained with isotropic characteristic.It is coarsening that follows the Ostwald ripening mechanism: smaller particles dwindle and larger particles grow; when the elastic strain is considered, plate precipitates tend to align along the elastically soft directions <01 > with anisotropic characteristic. The particles grow in the soft directions and coarsen further; particles dwindle in out of the soft directions. While the coarsening of the particles localized in the same row or column follows the rule: smaller particles shrink and larger ones grow.
Yuhong Zhao, Zheng Chen, and Xiaoling LiDepartment of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an 710072, China
