Quantitative analysis on microstructure evolution and tensile property for the isothermally forged Ti2AlNb based alloy during heat treatment

The microstructural features of the isothermally forged Ti-22Al-25Nb (at%) orthorhombic alloy during heat treatment were investigated quantitatively. The B2 grain size, thickness and volume fraction of lamellar precipitates under different heat treatment temperatures had been obtained by means of the image analysis software. The results indicated that it is very important to distinguish the different phase regions of solution treatment when investigating the effect of heat treatment on microstructure evolution. The quantitative relationships between heat treatment temperature, microstructure parameters and tensile properties were established. The thickness and volume fraction of precipitates could be controlled in the range of 0.16-1.63 μm and 7.9-28.2% respectively. The 0.2% yield stress and elongation agree well with the Hall-Petch relationship and those can be adjusted in the range of 680 MPa-1060 MPa and 610 MPa-960 MPa for RT and 650 °C 0.2% yield stress and 3.1%-8.8% and 8.2%-14.3% for RT and 650 °C elongation respectively by varying the microstructure parameters.