Theta method analysis for creep deformation and rupture time prediction of TiAl alloys at 760°C

Abstract

TiAl alloy has a good creep rupture specific strength. A θ projection method proposed by Evans et al. is a method that draw creep curve mathematically. This method can draw creep curve including tertiary creep by four parameters. Many researchers have studied on mechanical properties of TiAl alloy. However, there is few research report on TiAl alloy applied to θ projection method. This paper discusses the θ projection analysis method in order to investigate the creep properties of TiAl alloys. We evaluate the creep curve drawn by θ projection method. Experimental creep curves obtained at four stress levels were used. The creep curve and creep strain rate curve was redrawn exactly with the data until time to rupture time ratio as 0.9. The predicted minimum creep strain rate using estimated θ parameters showed a good agreement with the experimental data. Using Monkman-Grant rule, we lead to rupture time prediction expression. We predict creep rupture time with predicted minimum creep strain rate. Predicted creep rupture time show good approximation with experimental data. We concluded that creep rupture time prediction is possible by calculating minimum creep strain rate from estimated θ parameters.