Numerical Simulation Of CuAlNi Martensitic Transformation Wave Field

As the demand for special alloys increases, Shape Memory Alloys (SMA) becomemore and more common in engineering. They are of great value in the field such asaerospace profiles, precision medical instruments and industrial robots. Among them,alloy CuAlNi becomes the first choice in many occasions because of easy making andcheap. Its Shape memory effect is based on a reversible phase transformation–martensitic transformation, besides, martensitic transformation has made its own way inthe application of materials strengthening and deformation controlling for its uniqueproperties.However, there still remain some problems in its transformation mechanism, thistheoretical defect has greatly impeded its further engineering application, and withdrawits industrial development. So, studies on martensitic transformation mechanism will beof great value in overcoming this theoretical obstacle, in this way, these studies will notonly accomplish great academic benefits, but also lead a broader prospect.This paper did an exploratory work on the martensitic transformation mechanismof Shape Memory Alloy (SMA) CuAlNi. In order to provide more detail information oftransformation process, the scale barrier which Molecular Dynamics (MD) simulationbrings must be overcome, and build a foundation to do more transformation mechanismstudies on a larger scale. So in this paper, first, based on detail works on wave field andmartensitic transformation, it can be inferred that during the whole process ofmartensitic transformation, transformation field and microstructure are coupled witheach other in an interactive excitation model, and together they excite thetransformation to begin and promote the process; After that, the following thought ofwave field analysis is introduced aimed at simulating the wave field during thetransformation process, the use of finite difference method in stress-velocity staggergrid is also introduced; Then, also based on works about transformation energy barrier,the stress-strain relationships which are shown by MD simulations are being discussed.A brief constitutive equation laying stress on shear deformation and a criteria being usedto distinguish transformation processing region and no transformation region areintroduced; At last, Then the wave field of martensitic transformation is simulated anddiscussed, using the algorithm combined the finite difference method in stress-velocitystagger grid with the constitutive relationship mentioned above.During the simulation process, the main problems which the instability ofconstitutive relationship, anisotropy, and time-varying domain bring, are solved. Andthe result shows the unique characters which the martensite phase should have in its microstructure, and further more, its origin is discussed in-depth.