To study the effects of La on the microstructure and mechanical properties of refractory high entropy alloys,NbMoTiVSi0.2 alloys with different La contents were prepared.Phase constitution,microstructure evolution,com...To study the effects of La on the microstructure and mechanical properties of refractory high entropy alloys,NbMoTiVSi0.2 alloys with different La contents were prepared.Phase constitution,microstructure evolution,compressive properties and related mechanisms were systematically studied.Results show that the alloys with La addition are composed of BCC solid solution,eutectic structure,MSi2 disilicide phase and La-containing precipitates.Eutectic structure and most of La precipitates are formed at the grain boundaries.Disilicide phase is formed in the grains.La can change the grain morphologies from dendritic structure to near-equiaxed structure,and the average grain size decreases from 180 to 20μm with the increase of La content from 0 to 0.5 at.%.Compressive testing shows that the ultimate strength and the yield strength increase with the increase of La content,which is resulted from the grain boundary strengthening.However,they cannot be greatly improved because of the formation of MSi2 disilicide phase with low strength.The ductility decreases with the increase of La content,which is due to the La precipitates and brittle MSi2 disilicide phase.展开更多
基金The authors are grateful for the financial supports from the National Natural Science Foundation of China(51825401 and 52001114)the State Key Laboratory of Materials Processing and Die&Mould Technology(P2020-023)the Guangdong Introducing Innovative and Entrepreneurial Teams,China(2016ZT06G025).
文摘To study the effects of La on the microstructure and mechanical properties of refractory high entropy alloys,NbMoTiVSi0.2 alloys with different La contents were prepared.Phase constitution,microstructure evolution,compressive properties and related mechanisms were systematically studied.Results show that the alloys with La addition are composed of BCC solid solution,eutectic structure,MSi2 disilicide phase and La-containing precipitates.Eutectic structure and most of La precipitates are formed at the grain boundaries.Disilicide phase is formed in the grains.La can change the grain morphologies from dendritic structure to near-equiaxed structure,and the average grain size decreases from 180 to 20μm with the increase of La content from 0 to 0.5 at.%.Compressive testing shows that the ultimate strength and the yield strength increase with the increase of La content,which is resulted from the grain boundary strengthening.However,they cannot be greatly improved because of the formation of MSi2 disilicide phase with low strength.The ductility decreases with the increase of La content,which is due to the La precipitates and brittle MSi2 disilicide phase.
