Mechanical Properties, Microstructure and Fracture Mechanism of 95W-3.5Ni-1.5Fe Alloys at High Temperature

The mechanical properties and fracture characteristics of 95W-3.5Ni-1.5Fe alloys were investigated by tension in the temperature range of 400-1100 degrees C and the fracture mechanism was analyzed. The results show that the ultimate tensile strength (UTS) and the yield strength of the alloy decrease with the increasing temperature, while the elongation and the reduction of fracture surface area firstly increase up to the maximum value at 600 degrees C and then decrease with the increasing temperature. The improved ductility of the alloys in the temperature range of 400-600 degrees C is due to the enhanced comparable deformation capacity between tungsten and the matrix phases by ductile-brittle transformation of tungsten phase. Above 700 degrees C, dynamic recrystallization occurs in the matrix, which deteriorates the strength of tungsten/matrix interfaces. Hence, the applied stress can not be transited from the matrix to tungsten particles and the comparable deformation capacity of tungsten and matrix is reduced, resulting in a sharp decrease in strength and toughness of alloys.