Study on a statistical unit cell model for Ni3Al-base superalloy

Ni3Al-base superalloys, which are widely used as high temperature structural materials in aerospace applications, have a high volume fraction of Ni3Al (γ′ phase) precipitates distributed within a matrix of solution-strengthened Ni (γ phase). Various experimental results show that the γ′ precipitate size in Ni3Al-base superalloys is different and random in a certain scale range. For the mechanical properties of alloys will be affected by their microstructural features, a new statistical unit cell model is proposed to describe the macro mechanical properties by considering the effects of γ′ precipitate size on the properties of the superalloys. In this model, the typical microstructure of alloys is analyzed and the γ′ precipitate size distribution is studied by statistical method first. According to the probability distribution theory, a relationship between the macro mechanical properties of alloys and the micro mechanical properties of the unit cells with different γ′ precipitate sizes is developed. The micro mechanical properties of the unit cells can be calculated by the unit cell method. Then, the macro mechanical properties can be predicted. Alloy IC10, a newly developed nickel-base superalloy, is a typical multiphase alloy with about 65% volume fraction of γ′ phase. Its mechanical properties at different temperatures are obtained by tensile tests and used to verify the statistical unit cell model. Simulation results show that the statistical unit cell model can be used to predict the mechanical properties of alloy IC10 successfully. In order to study the effects of the number of samples on the accuracy of the statistical model, six cases with different samples numbers were introduced. Comparison results show that: (1) the prediction accuracy will increase as more samples are used in the statistical model; (2) when the number of samples used in the statistical model is greater than a certain value, the prediction accuracy will be saturated.