Refined microstructure and enhanced mechanical properties in Mo-Y2O3 alloys prepared by freeze-drying method and subsequent low temperature sintering

The ultrafine Mo-Y 2 O 3 composite powders were successfully synthesized by innovative freeze-drying method. Consequently, the freeze-dried Mo-Y 2 O 3 composite powders with high sintering activities possess an average grain size of 54 nm. After low temperature sintering at 1600 °C, the Mo-Y 2 O 3 alloys maintaining a high density (99.6 %) have the finest grain size (620 nm) comparing with available literature about oxide dispersion strengthened molybdenum alloy (ODS-Mo). The oxide particles remain their small size (mainly <50 nm) within Mo grains and at Mo grain boundaries. Furthermore, the Y 5 Mo 2 O 12 particles were firstly observed within Mo matrix, and its formation can absorb nearby oxygen impurities, which involves the purification of Mo matrix. The mechanical properties show that Mo-Y 2 O 3 alloy possess a high hardness of 487 ± 28 HV 0.2 , a high yield strength of 902 MPa, a high compressive strength of 1110 MPa, respectively. Our work suggests that freeze-drying and subsequent low temperature sintering can shed light on the preparation of ultrafine ODS-Mo alloys with high performance.