Constitutive modelling and mechanical properties of a tungsten heavy metal alloy

The mechanical behaviour of a tungsten heavy metal alloy (WHA) with potential use as a kinetic energy penetrator is investigated. From quasi-static experiments the deduced flow stress curves are discussed and the ultimate tensile stress is compared to the suppliers data. Dynamic mechanical properties related to tensile loading are measured at strain rates up to 400 s-1 and at temperatures from 20 °C to about 500 °C. From the experimental data parameters for the constitutive equations developed by Johnson and Cook (J&C) as well as Zerilli and Armstrong (Z&A) are determined. The specific heat capacity is measured at temperatures from 20-200 °C and is used for calculations of the deformation induced temperature increase. From the extracted models isothermal and adiabatic flow stress curves are calculated and compared to experiments and available literature data. The quasi-static experiments show a linear behaviour up to about 1300 MPa followed by a rather weak strain hardening, and fracture occurs at a nominal strain of the order of 5-10 %. The ultimate tensile stress is 1340 ± 30 MPa which is close to the value of 1350 MPa given by the manufacturer. At high strain rates or high temperatures the J&C model deviates about 5-10 % from experimental results, while the Z&A model shows a better agreement with the collected data. It should be emphasised that the Z&A model used in this work is developed for materials with body centred crystals whereas the WHA is a composite with both face centred- and body centred crystals.