Deformation, shape memory and superelastic effects of high entropy alloy single crystals based on cocktail effect

2019 Fiscal Year Final Research Report

• Project/Area Number: 18K18949
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 26:Materials engineering and related fields
• Research Institution: Osaka University
• Principal Investigator: Yasuda Hiroyuki 大阪大学, 工学研究科, 教授 (60294021)
• Co-Investigator(Kenkyū-buntansha): 趙 研 大阪大学, 工学研究科, 講師 (00633661)
• Project Period (FY): 2018-06-29 – 2020-03-31
• Keywords: ハイエントロピー合金 / カクテル効果 / 形状記憶合金 / 超弾性

Outline of Final Research Achievements

Single crystalline specimens of bcc-HfNbTaTiZr high entropy alloys can be obtained from the coarse grains and the deformation behavior was investigated. As a result, the single crystals exhibit a high yield strength around 1000MPa at room temperature. It is also noted that high strength can also be obtained at 600℃ due to the precipitation of the hcp phase. The deformation behavior of non-equiatomic (TiZrHf)100-x(NbTa)x and V-doped alloys was also examined. The phase constituent and phase transformation of the non-equiatomic alloys are found to be similar to those of Ti-based and Zr-based alloys. However, at present, elastic anomaly, shape memory effect and superelasticity which are typical in β-Ti alloys cannot be observed.

Free Research Field

材料強度学

Academic Significance and Societal Importance of the Research Achievements

申請者の知る限り、HfNbTaTiZrハイエントロピー合金のバルク単結晶を用いて、その変形挙動に関する研究を行ったのは、申請者らが世界で初めてである。さらに、HfNbTaTiZr合金を初めとするbccハイエントロピー合金をβチタン合金に見立てて、構成元素を(TiZrHf)と(NbTa)とに分けて考え、形状記憶・超弾性合金としての可能性を探るアイディアは、申請者が世界で最初に提案したものである。学会発表などを通じて、こうしたアイディアが広まり、新しい研究開発の潮流が生まれている。