Effect of aging treatment on L12 precipitated phase and mechanical properties of (FeNiCoCr)90Al5Ti5 high entropy alloy

Abstract

The morphology and phase stability of precipitated phases are essential for regulating mechanical properties of alloys. The (FeNiCoCr)90Al5Ti5 high entropy alloy was prepared by low-speed ball milling and hot-press sintering method, and the effects of high-temperature (1150 ℃) and medium-temperature (850 ℃) aging treatment on the types, morphology, distribution and mechanical properties of precipitated phases in the alloy were investigated. The results show that the compressive strain of the prepared alloy reaches 47%, and the yield strength and ultimate compressive strength are 948 MPa and 1684 MPa, respectively. The high strength is due to the strengthening effect of the L12 structure nano-precipitation phases within the crystal. After aging at 850 ℃ for 10 h, the L12 precipitated phases grow into equiaxed grains with a size exceeding 10 μm, and some of them transform into a thin lamellar HCP structure η phases, which leads to the decrease of the yield strength and ultimate compressive strength of the alloy. After aging at 1150 ℃ for 2 h, the intracrystalline L12 nano-precipitated phases completely redissolve, which leads to a drastic decrease in the yield strength and ultimate compressive strength of the alloy.

Keywords

• high entropy alloy
• precipitated phase
• aging treatment
• compression property