Molecular Dynamics Simulation Of Martensitic Nucleation In CuAlNi Alloy

In recent years, the unique shape memory effect of thermo-elastic martensitehas attracted much attention in the field of industrial applications. As a carrier,CuAlNi alloy has encountered a broad prospect in development for its variousadvantages. It’s shape memory principle is based on a characteristic, that is, thematerial can conduct the reversible martensitic transformation under a certaincondition. However, the mechanism of martensitic transformation is still not veryclear so far, resulting in great restriction in CuAlNi alloys’ practical engineeringapplications. In order to make further exploration to solve this problem, thoroughand meticulous analysis on the mechanism of martensitic transformation must bemade.The main purpose of this paper is to explore the nucleation mechanism ofmartensitic transformation in CuAlNi ternary shape memory alloy. To get thespecific pattern of martensitic transformation nucleation, on the basis of preliminarywork, this thesis is combined with MEAM potential function which has beenobtained already, and the method of molecular dynamics simulation is introduced asthe main research means to produce the numerical simulation, which is purposed toget the most accurate details of martensitic transformational nucleation.In order to further promote the research work on mechanism of the CuAlNialloy martensitic transformation, this paper took the nucleation of transformation asthe starting point, and based on literature survey and preliminary work, firstly, weproposed a specific model of the martensitic transformation nucleation and growthmechanism, besides, we made a detailed analysis on the space structure andmechanical performance of the large amount of spatial configuration data, whichwas obtained from simulation and it revealed the relationship between nucleationand the emergence and development of dislocation, at the end, we verified ourmodel’s correctness. In the data analysis phase, this paper has developed a uniqueset of numerical algorithms, including the following items: we got microscopiccriteria to determine whether the phase transition has occurred or out, that is, wedisplayed the lattice type with different colors. This algorithm is more visible andaccurate, which has provided strong foundation for subsequent analysis. Weestablished a numerical method based on the Burgers vector to observe dislocations,in this way, we initially got the specific development of dislocation in themartensitic transformation process. Moreover, as an assist judgment of lattice sheardeformation, we also compared the strain fringes on the key steps in the transformation process.