Structure evolution of Y2O3 and consequent effects on mechanical properties of W–Y2O3 alloy prepared by ball milling and SPS

Abstract

Aggregation of Y2O3 particles with relatively large size along grain boundaries is a main limiting factor for performance improvement in W–Y2O3 alloys. In order to tailor the distribution and achieve size refinement of Y2O3 dispersoids, W–Y2O3 alloy was prepared using ball milling with extended milling time and subsequent spark plasma sintering (SPS) in this study. Microstructure evolution of Y2O3 during the preparation process was characterized in detail using X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). Mechanical properties of SPSed alloy were evaluated in terms of microhardness, three-point bending and compression tests. Structure transformation of Y2O3 from BCC to FCC during the process of ball milling and subsequent sintering was first identified in W–Y2O3 alloy in this study. Compared with the raw micron sized Y2O3 powders, the transformed Y2O3 dispersoids experienced significant size refinement. Around 76% of the nanosized Y2O3 dispersoids were distributed inside grain interior, and they exhibited semi-coherent relationship with tungsten matrix. These microstructural characteristics contributed to the high compressive strength of 1804.2 MPa and microhardness of 625.7 HV in the SPSed W–Y2O3 alloy.