Abstract
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•The Mo-Y2O3 powders of 54 nm were prepared by novel freeze-drying.•The Mo-Y2O3 alloys possess Mo grains of 620 nm meanwhile its density is 99.6 %.•Nano Y5Mo2O12 particles of <50 nm uniformly distribute within Mo matrix.•The hardness of alloys is as high as 487 HV0.2.•The yield strength of alloys is as high as 902 MPa.
The ultrafine Mo-Y2O3 composite powders were successfully synthesized by innovative freeze-drying method. Consequently, the freeze-dried Mo-Y2O3 composite powders with high sintering activities possess an average grain size of 54 nm. After low temperature sintering at 1600 °C, the Mo-Y2O3 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 Y5Mo2O12 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-Y2O3 alloy possess a high hardness of 487 ± 28 HV0.2, 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.