Microstructure and mechanical properties of W-Zr reactive materials

Three different batches of tungsten-zirconium (W-Zr) reactive material were prepared by hot-pressing elemental powder mixtures. The first sample had a Zr:W mass ratio of 66:34. The second used zirconium hydride (ZrH₂) with a (ZrH₂):W mass ratio of 66:34. The third had a Zr:W mass ratio 43:57. These batches were numbered #1 to #3. To investigate the mechanical properties of the W-Zr reactive materials, samples were subjected to different strain rates using a materials testing machine and a modified split Hopkinson pressure bar (SHPB). The quasi-static compressive strengths of the three sample batches all exceeded 1022 MPa, with batch #1 sample having the highest value at about 1880 MPa. This could be ascribed to the sample exhibiting a more transgranular and dimpled fracture in the W₂Zr intermetallic phase, as demonstrated by the microstructure of the fracture surface, observed by scanning electron microscopy (SEM) using an energy-dispersive spectrometer (EDS). To perform a constant strain rate experiment on this high-strength but brittle material, ramp loading using copper sheet was adopted in this study. All of the samples produced strong, bright flames when subjected to shock loading and exhibited a high compressive strength of approximately 1060 to 2690 MPa. High-resolution X-ray diffraction (XRD) was performed on the original samples and residues after the SHPB test, showing that the Zr and ZrC phases of the batch #1 and batch #3 samples, and the ZrC_0.32H_1.2 phase of the batch #2 sample are the active components in the reaction with air. Some small balls of ZrO₂ reaction product were found not to exhibit any crystalline tungsten oxide on the residue surface. These results suggest that the batch #1 reactive material has huge potential to take the place of inert steel because of its high strength and high energy level, as well as having a density close to that of steel.