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Tuesday, October 19, 2004 - 8:30 AM
PHA 2.1

Application of CALPHAD in R&D of Advanced Titanium Alloys

J. Shen, General Research Institute for Non-ferrous Metals of Beijing, Beijing, China

CALPHAD is being used in the development of the advanced Titanium alloys. Following are some examples of our work.

(1) Design of anti-combustion Ti alloy.

The utilization of Ti alloys in aircraft has been limited due to the possibility of "Ti fire" accidents. Adiabatic burning temperatures (Tad) were calculated for some systems with CALPHAD. It reveals that the combustion properties of alloys are directly related with Tad. Combined with thermal conductivity, Tad has been successfully used in finding new anti-combustion Ti alloys.

(2) Optimization of compositions and heat treatment processes of Ti alloys with high elastic modulus and strength.

The influence of some elements on the phase compositions of the Ti alloys is studied by CALPHAD. Combined with the EAM potential, which can predict the mechanical properties of phases with known compositions, new Ti alloys with high elastic modulus and strength was designed for the shell materials of spacecraft. Tβ of the alloys was calculated by CALPHAD to guide the heat treatment processes to eliminate the anisotropy of the alloy sheets.

(3) Analysis of the effects of thermal exposure on the properties of the Ti alloys.

Degradation under thermal exposure is a problem of Ti alloys used in aerial engines. The formation conditions of some precipitated phases during thermal exposure were studied by CALPHAD. The alloy compositions, melting and heat treatment processes were then designed to reduce the degradation effects.

(4) Calculation of the partition coefficients and solidifying temperatures for O-Phase Ti alloy.

Alloys based on ordered orthorhombic Ti2 AlNb phase are promising materials with good combination of high temperature strength, room-temperature ductility and fracture toughness. The partition coefficients and solidifying temperatures were calculated by CALPHAD. These parameters play an important role in selecting the process parameters to reduce the segregation and pores in the ingots.


Summary: Some examples are presented about the application of CALPHAD in the development of new titanium alloys with special requirement, such as anti-combustion, high elastic module, good mechanical properties at high temperature, good combination of of high temperature strength, room-temperature ductility and fracture toughness etc.