Phase Constituent and Microhardness of As-Cast and Long-Time Annealed AlxCo2−xCrFeNi Multicomponent Alloys
- 113 Downloads
The phase constituent and microstructure of arc-melted AlxCo2−xCrFeNi multicomponent alloys, in both the as-cast state and after annealed at 800 or 1000 °C for 30 days, were experimentally investigated by scanning electron microscopy and x-ray diffraction. Different phase constituents were obtained in these alloys. The Al0.25Co1.75CrFeNi alloy was composed of a single FCC phase in both as-cast and 1000 °C annealed states. Small amount of B2 phase precipitated after 800 °C annealing. A eutectic structure was observed in the Al0.75Co1.25CrFeNi alloy. Its morphology kept, but small amount of σ phase separated, after being annealed at 800 °C for 30 days. In the AlxCo2−xCrFeNi (x = 1.25-1.75) alloys, a single B2 phase was obtained in the as-cast state, it would turn to two-phase of BCC + B2 after 800 °C or 1000 °C annealing. The as-cast AlCoCrFeNi alloy was also composed of a single B2 phase, it would transform to four phases of BCC + B2 + FCC + σ after 800 °C annealing, and to two phases of B2 + FCC after 1000 °C annealing for the σ phase is not stable at 1000 °C. Moreover, experimental results indicated that the alloy hardness increased with the Al content. The existence of the σ phase could obviously harden the alloy. Except for the alloys with σ precipitation, the hardness of the annealed alloys was lower than that of the as-cast ones. In addition, increasing the annealing temperature coarsened the grains and softened the alloys.
KeywordsAl-Co-Cr-Fe-Ni annealing microstructure multicomponent alloys
The authors gratefully acknowledge the financial support from National Natural Science Foundation of China (Nos. 51771035 and 51671036), Natural Science Foundation of Jiangsu Province (BK20161190), Postgraduate Research and Practice Innovation Program of School of Materials Science and Engineering Changzhou University (CL17SJ-003) and the Priority Academic Program Development of Jiangsu Higher Education Institutions.
- 28.J.C. Rao, H.Y. Diao, V. Ocelík, D. Vainchtein, C. Zhang, C. Kuo, Z. Tang, W. Guo, J.D. Poplawsky, Y. Zhou, P.K. Liaw, and J.T.M. De Hosson, Secondary Phases in AlxCoCrFeNi High-Entropy Alloys: An In Situ TEM Heating Study And Thermodynamic Appraisal, Acta Mater., 2017, 131, p 206-220CrossRefGoogle Scholar
- 35.X. Wu, W. Zhang, L. Qin, and C. Zhang, Effects of Annealing Treatment on Microstructure and Mechanical Properties of AlCoCrFeNi High-entropy Alloy, Hot Work. Technol., 2015, 44(8), p 220-222Google Scholar