Numerical Simulation Of Solidification Structure Of Ti Alloy During Vertical Centrifugal Casting

Due to its excellent general properties, such as high specific strength and good creep-resisting property under high temperature, Titanium alloy is regarded as one of the backbone materials in aeronautics, aviation and military industries. Titanium alloy castings are generally manufactured by vertical centrifugal casting. Thus, the rules of flow, heat transfer and structure formation of metal in the vertical centrifugal field are important to obtain Titanium alloy castings of excellent properties.The grain structure formation and evolution during the vertical centrifugal casting solidification processes of Ti6Al4V alloy are simulated, based on a finite differential method (FDM) for macroscopic field calculation and a cellular automaton technique (CA) for microscopic modeling of grain nucleation and growth.The mathematical model and numerical techniques of flow and solidification of titanium alloy melts in the vertical centrifugal field has been established.By means of the above-mentioned mathematical models and numerical techniques, the influences of processing parameters to grain structure formation, such as the rotational velocity, superheat and mould-preheating temperature are presented and investigated on the basis of calculation for the flow field and temperature filed. Research results of titanium alloy microstructure show that equiaxed grain exists in the vertical centrifugal filed, and the mean grain size decreases with the increasing of rotational velocities. The higher the melt superheat, the larger the equiaxed zone accompanied by a coarser grain size. Obvious impact can not be found on the structure of casting with the increment mould temperature.The experimental castings were designed, which were used to study the regulation of grain structure formation. The material used in the experiment was Ti6Al4V and the rotational velocities were 0rpm, 160rpm and 280rpm individually. The regulation of grain structure formation under gravity casting and vertical centrifugal casting has been investigated and the comparison between the experimental and the numerical results shows good agreement.