Abstract
A NbMoTaWVTi refractory high entropy alloy (HEA) has been successfully synthesized by mechanical alloying (MA) and spark plasma sintering (SPS). The microstructure and mechanical properties of this alloy are investigated. It is observed that only two types of body-centered cubic (BCC) solid solutions are formed in the powders after ball milling for 40 h. However, a new face-centered cubic (FCC) precipitated phase is observed in the BCC matrix of bulk material consolidated by SPS. The FCC precipitated phase is identified as TiO, due to the introduction of O during the preparing process of HEA. The compressive yield strength, fracture strength, and total fracture strain of the consolidated bulk HEA are 2709 MPa, 3115 MPa, and 11.4%, respectively. The excellent mechanical properties can be attributed to solid solution strengthening and grain boundary strengthening of the fine-grained BCC matrix, as well as the precipitation strengthening owing to the formation of TiO particles.
Highlights
According to the traditional alloy design theory, ordered phases or intermetallic compounds will form as the number of alloying elements increases
They propose a new alloy system, termed high entropy alloys (HEAs), which contain at least five principal elements, each having the atomic percentage between 5% and 35% [1,2]
These powders are subsequently heated by a spark plasma sintering machine
Summary
According to the traditional alloy design theory, ordered phases or intermetallic compounds will form as the number of alloying elements increases. Yeh et al observes that simple solid solution phases, instead of intermetallic compounds, are formed in an equiatomic quinary alloy. They propose a new alloy system, termed high entropy alloys (HEAs), which contain at least five principal elements, each having the atomic percentage between 5% and 35% [1,2]. Since the development of HEAs, a substantial number of studies on HEA have been performed Some of these studies are focused on alloys comprised of elements with low melting points, such as AlCoCrCuFeNi system alloys [3,4], commonly exhibiting high ductility and low strength.
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