Directional Solidification Structure Simulation Of Titanium Alloy

With low density, together with high strength-to-weight ratio and high temperature creep resistance, titanium alloys become more and more popular in the astronavigation and navigation now. Directional solidification technique can control the growth direction of solidification structure, which can largely improve mechanical properties and high temperature properties of alloys in special directions. The technique of solidification structure simulation is a scientific, effective and applied method to study directional solidification structure of titanium alloy, especially for the process of directional solidification under dynamic pulling state.Based on a finite differential method (FDM) for macroscopic field calculation and a cellular automaton technique (CA) for microscopic modeling, the model of directional solidification simulation of titanium alloy is established. And the process of dynamic simulation, which can reflect the growth state of directional solidification structure of titanium alloy under the pulling course, is realized by compiling numerical program with VC language, which can be used to study the structure evolutions under the dynamic moving process.Under the condition of directional solidification, the technological parameters, such as pulling velocity, the degree of melt superheat and the distance between zone of heating and cooling liquid are the main factors that influence the temperature field and structure during the solidification process. Numerical simulation for titanium alloy(Ti-49Al) with different parameters have been carried out in this paper. The simulation results show that the temperature gradient of the solidification front increases and the shape of solidification front changes from convex to flat, as well as columnar grain spacing increases and grain numbers decreases with the pulling velocity decreases. In addition, the temperature gradient and columnar grain spacing increase, as well as the grain numbers decreases with the increasing of the melt superheat. However, the temperature gradient decreases, and columnar grain spacing increases with the increasing of distance between zone of heating and cooling liquid.Directional solidification experiment has been designed in this paper, and the pulling experiment of titanium alloy (Ti-49Al) is done. The numerical simulation result and experimental result shows good agreement, which indicate the accuracy of established model and the investigated regulation, as well as it can be used to direct the actual production.