Refinement of Al-containing particles and improvement in performance of W-Al-Y2O3 alloy fabricated by a two-step sintering process

Abstract

The Al-containing particles in ODS alloys with Al addition usually exhibit relatively large size, and inevitably result in a limited improvement in mechanical properties. In this paper, W-Al-Y2O3 alloy was prepared by a two-step sintering process to refine the Al-containing particles. Microstructure evolution of dispersoid particles was characterized by scanning electron microscope (SEM), electron probe microanalysis (EPMA) and transmission electron microscopy (TEM). During the first holding step at 1000 °C, the dissolved Al precipitated directly from W matrix, where the formed γ-Al2O3 particles were nano-sized and developed a coherent relationship with W matrix. This coherent relationship hindered transformation of γ-Al2O3 into submicron-sized α-Al2O3. Moreover, the nano-sized γ-Al2O3 contributed to formation of fine Y3Al5O12 dispersoid particles with the sintering temperature further increased to 1600 °C. 71% of the dispersoid particles were distributed within grains and most of them were nano-sized γ-Al2O3 and Y3Al5O12, giving a fine grain size of 0.49 μm. Due to the refined microstructure, the compressive strength and microhardness of W-Al-Y2O3 alloy reached 2545.9 MPa and 787.8 HV, respectively.