Fatigue properties and characterization of tungsten heavy alloys IT180 & D176

Fatigue properties of tungsten heavy alloys IT180 (W-3.5Ni-1.5wt.%Cu) and D176 (W-5Ni-2.5wt.%Fe) have been determined using constant amplitude, stress-controlled high cycle fatigue tests at room temperature. The results show that the endurance limits for the IT180 and D176 alloys are about 210 and 425 MPa respectively. The fatigue strength coefficients for the two alloys have been determined as 1048 and 3000 MPa and the corresponding strength exponents are − 0.11 and − 0.13 respectively. Strain-controlled fatigue tests were also performed to observe the response of the materials and determine the cyclic stress-strain curves of the alloys using the multiple step method. Cyclic hardening was observed in both alloys and the cyclic strain hardening exponent for the D176 alloy had a value of 0.08. The fatigue response of the material is strongly affected by surface roughness, residual porosity, pore size and its distribution. Microstructures and the fracture surfaces of the samples were characterized by scanning electron microscopy and energy dispersive spectroscopy.