Microstructure and mechanical properties of W-Zr reactive materials

Abstract

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 1022MPa, with batch #1 sample having the highest value at about 1880MPa. 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 2690MPa. 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 ZrC0.32H1.2 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.