Effect of vacuum heat treatment on microstructure evolution and mechanical properties of 93W-4.9Ni-2.1Fe-(ZrB2) alloys

Abstract

93W-4.9Ni-2.1Fe-(0.75ZrB2) alloys (wt%) were subjected to liquid phase sintering and vacuum heat treatment to optimize the microstructure and improve mechanical performance. Microstructural observations demonstrated that W–W continuity, dihedral angle and connectivity after heat-treatment remarkably decreased by 0.75, 10° and 0.7, respectively. Meanwhile, matrix phase volume fraction also increased by nearly 3%, which overcame the negative effects of non-homogeneous microstructure. However, densification and W grain size exhibited marginal changes. Mechanical properties strongly varied with the change of microstructural characteristics. Particularly, as matrix phase volume fraction increased and W–W contiguity decreased dramatically, elongation showed a distinct increasing tendency (from 18.6% to 22.4% in 93W alloys and from 17.5% to 19.5% in 93W-0.75ZrB2 alloys, respectively). Excellent W-matrix bonding strength improved the tensile property, while microstructure uniformity caused the decrease of hardness value (about 28 HV1). Furthermore, the relationship between mechanical properties and fracture mode was analyzed.