Refined microstructure and enhanced mechanical properties of AlCrFe2Ni2 medium entropy alloy produced via laser remelting. (10th February 2022)

• Record Type: Journal Article
• Authors: Han, Tianyi; Liu, Yong; Liao, Mingqing; Yang, Danni; Qu, Nan; Lai, Zhonghong; Zhu, Jingchuan
• Is Part Of: Journal of materials science & technology. Volume 99(2022)
• Page Start: 18
• Page End: 27
• Publication Date: 2022-02-10
• Subjects: Medium entropy alloy -- Laser remelting -- Microstructure -- Nano-indentation -- Strengthening mechanism; Metals -- Periodicals; Materials science -- Periodicals; Materials science; Metals; Periodicals; 620.1105
• DOI: 10.1016/j.jmst.2021.05.033
• Languages: English
• ISSNs: 1005-0302

Abstract

Highlights: Laser remelted AlCrFe2 Ni2 medium entropy alloy showed nano-size weave-like microstructure with alternated ordered B2 and disordered BCC phases. The rapid cooling rate of laser remelting promoted the refinement of grains. The yield strength of remelted medium entropy alloy derived from nano-indentation tests could reach 1647.2 MPa. Dislocation and precipitation are dominant strengthening mechanisms in the laser remelted medium entropy alloy. Abstract: A Co-free as-cast AlCrFe2 Ni2 medium entropy alloy (MEA) with multi-phases was remelted by fiber laser in this study. The effect of laser remelting on the microstructure, phase distribution and mechanical properties was investigated by characterizing the as-cast and the remelted AlCrFe2 Ni2 alloy. The laser remelting process resulted in a significant decrease of grain size from about 780 μm to 58.89 μm (longitudinal section) and 15.87 μm (transverse section) and an increase of hardness from 4.72 ± 0.293 GPa to 6.40 ± 0.147 GPa (longitudinal section) and 7.55 ± 0.360 GPa (transverse section). It was also found that the long side plate-like microstructure composed of FCC phase, ordered B2 phase and disordered BCC phase in the as-cast alloy was transformed into nano-size weave-like microstructure consisting of alternating ordered B2 and disordered BCC phases. The mechanical properties were evaluated by the derived stress-strain relationship obtained from nano-indentation tests data. The results showed that the yield stress increased from 661.9 MPa to 1347.6 MPa (longitudinal section) and 1647.2 MPa (transverse section) after remelting. The individual contribution of four potential strengthening mechanisms to the yield strength of the remelted alloy was quantitatively evaluated, including grain boundary strengthening, dislocation strengthening, solid solution strengthening and precipitation strengthening. The calculation results indicated that dislocation and precipitation are dominant strengthening mechanisms in the laser remelted MEA. Graphical abstract: Image, graphical abstract