Activated sintering effect of Fe element on tungsten via spark plasma sintering

Abstract

Full-densely activated sintered W(Fe) was prepared by spark plasma sintering technique. The effects of Fe content (0 ∼ 1.0%(wt.%)) on relative density, microstructure and mechanical properties were discussed. The mechanisms of solution strengthening effect and grain boundary strengthening effect of Fe addition were revealed by calculating dislocation energy and vacancy formation energy. The results indicated that the relative density and the grain size were the Exponential function and the Boltzmann function of Fe contents, respectively. Full-dense W(Fe) could be obtained with ≥ 0.75 %Fe added. The W(Fe) microstructure consisted completely of solid solution. The microhardness was monotonically increased due to the increase of relative density with Fe content increased, while the flexural strength and fracture toughness showed a nonmonotonic trend depending on the interaction of relative density and grain size. Specifically, the mechanical properties were all increased accompanied by the appearance of the typical transgranular fracture and a novel “micro-area transgranular fracture” with Fe content increased from 0.75% to 1.0%. The increases in mechanical properties were attributed to the combined action of the solution strengthening effect and grain boundary strengthening effect. The decreases of the dislocation energy and vacancy formation energy led to the increases of the deformation resistance and grain bonding strength, respectively, which resulted in the strengthening and toughening effects.