Tensile property and deformation behavior of a directionally solidified Ni-base superalloy

Tensile behavior of directionally solidified Ni-base superalloy DZ951 was studied in the temperature range of 20–1100 °C. Extensive TEM investigations were performed after tensile test to fracture. The yield and tensile strengths initially decrease slightly with temperature and reach minima at around 700 °C. With further increase in temperature, the yield and tensile strengths increase to maxima at about 760 °C and then decrease sharply. In contrast to changes in strength with temperature, elongation is without significant change from 20 to 700 °C and then decreases to a minimum at 760 °C. Beyond that point an increase in elongation with respect to temperature occurs. The intermediate temperature brittleness behavior for DZ951 alloy is remarkable. The deformation microstructures could be classified in three regimes. At low temperatures, the deformation was dominated by γ′ shearing by pairs of a/2〈1 1 0〉 dislocations. At high temperatures, the deformation was dominated by γ′ by-pass. Intermediate temperatures exhibited transitional behavior. The ductility minimum at 760 °C is due to strain localization mainly caused by stacking faults.