Influence of minor elements additions on microstructure and properties of 93W-4.9Ni-2.1Fe alloys

Effects of elements rhenium and chromium additions on properties and microstructure of 93W-4.9Ni-2.1Fe alloys were investigated. Optical microscope (OM), scanning electron microscope (SEM) and EDAX energy spectrometer were used to characterize the microstructure and compositions of the alloys, respectively. The tensile strength and elongation of alloys were evaluated using the quasi-static tensile testing machine, and the relative densities of the alloys were evaluated using the Archimedes water immersion method. The experimental results indicated that when elements Re and Cr were in the range of 0-1.0 wt.%, relative density, elongation, tensile strength of 93W-4.9Ni-2.1Fe alloys varied from 99.4%, 26.4%, 997.2 MPa without Re additions to 99.5%, 8.6%, 1161.2 MPa with 1.0 wt.% Re addition, respectively. Rhenium generated solid-solution strengthening, grain refinement, reducing ductile tearing and increasing transcrystalline fracture, which resulted in the ductility reduction and the strength increase of the heavy alloys. With the increase of Cr content from 0-1.0 wt.%, the tensile strength, relative density and elongation of 93W-Ni-Fe alloy reduced from 997.2 MPa, 99.3%, 15% to 844.4 MPa, 95.2%, 5-7%, respectively. Element Cr formed inter-phases with elements W, Ni, Fe and O and gathered along the interface of the alloys, which induced interfacial cohesion and resulted in lower mechanical properties of 93W-Ni-Fe alloys.