Investigation of hot extruded GW84 alloy on high temperature tensile properties and microstructure evolution

The tensile properties and microstructure of hot extruded GW84 alloy stretching at 200 °C, 250 °C and 300 °C were investigated. The results showed that the alloys had excellent high temperature mechanical properties, when stretching at 250 °C, the ultimate tensile strength of alloy reached peak value, 393 MPa, and the tensile strength stretching at 300 °C reached 354 MPa. During high temperature tensile process, the microstructure markedly changed, which is not recognised in previous researches. Stretching at 200 °C, the precipitate phase was still metastable β′ phase. However, when stretching at 250 °C, the nano β′ precipitate transformed into nano β phase (β′ → β), and the precipitation mechanism is mainly inoculation nucleation of β phase. When stretching at 300 °C, the number of β precipitates increased significantly at triangular grain boundaries, which grew up to sub-micron particles, and precipitation mechanism is mainly growth and coarsening.