Investigation Of Solidification Path And Properties Of Multi-component Multiphase Alloy

The solidification mechanism,phase transition pattern and the mechanical properties of the alloys are the important aspects that the field of mechanical engineering.Amature and efficient calculating model in the solidification process of the binary alloys system has already built,but in reality,the mainstreams are the ternary alloys,even the multicomponent alloys.However,when it comes to the ternary alloys,there is only a relatively perfect solidification theory system for the eutectic type,and it is more complex about the phase transition of monetectic type,peritectic type,quasiperitectic type and so on.Reseaching on the solidification path of multicomponent multiphase alloy is one of the significant directions to control the solidification condition and process,so that the aim at improving material properties will be reachable.In this paper,based on the Thermo-Calc application and the transport simulation made by our research group,the Al-Si-Mg ternary quasiperitectic alloys different in component,dendrite morphologies and Solid-back Diffusion degree were choose to do the solidification path calculation.The results of the calculation conveys that all the three factors mentioned above can change the Al-Si-Mg alloy's solidification path,and the effections from unified SBD parameters are more balanced than the Solid diffusion parameters to the path.The ternary Al-Cu-Si eutectic alloys with different compositions were selected to conduct solidification experiments under different cooling rates,so that we got the statistics on alloys' cooling conditions,second dendrite space,microhardness and so on.So we checked all the alloys' solidification paths and analyzed the growth mechanism of eutectic.The calculation results of the Al-Si-Mg alloys' cracking susceptibility shows that the alloys which are more likely to produce more eutectic phases has a higher cracking susceptibility.We choose Al-Cu-Mg alloys which has the ternary quasiperitectic transformation in different components to do the solidification experiments in different cooling rate conditions and the properties tests,then analyzed influences from the component and cooling rate to the microstructure and properties as well as the solidification mechanism of quasiperitectic with the phase diagram calculation result.The result shows that the Al-Si-Mg alloys which has the ternary quasiperitectic transformation continued to the ternary eutectic transformation,and the alloys which had the quasiperitectic transformationare equiped with better hardness than the alloys which only had the ternary quasiperitectic transforamtion.Using the Thermo-Calc's light alloys data base to try thermodynamic calculations on Al-Cu-Sn alloys,and we confirmed Al-6Cu-4Sn,Al-10Cu-10 Sn and Al-20Cu-30 Sn alloys' solidification paths with the microstructure we got from the experiments,also measured the hardness and the compression performance of the Al-Cu-Sn alloys in defferent components,and analyzed the monetectic transformation Precipitated phase's influences on properties.The effects of the addition of elements Mo and Y on the microstructure and properties of Ti-44Ni-6Cu were studied.The experimental results show that when the Mo content is0.6wt.%,More white phases are formed at the grain boundaries,which lead to As the hardness increases,the strength and plasticity deteriorate rapidly;however,Y has a limited effect on the performance of the specimen.