Alloying behavior and deformation twinning in a CoNiFeCrAl0.6Ti0.4 high entropy alloy processed by spark plasma sintering

• Published in: Journal of alloys and compounds Vol. 553; pp. 316 - 323
• Main Authors: Fu, Zhiqiang, Chen, Weiping, Fang, Sicong, Zhang, Dayue, Xiao, Huaqiang, Zhu, Dezhi
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 15.03.2013; Elsevier
• Subjects: Alloy systems; Alloying; Applied sciences; Body centered cubic lattice; Condensed matter: structure, mechanical and thermal properties; Deformation twinning; Elasticity. Plasticity; Entropy; Exact sciences and technology; Fatigue, brittleness, fracture, and cracks; High entropy alloys; Mechanical alloying; Mechanical and acoustical properties of condensed matter; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Mechanical properties of solids; Metals. Metallurgy; Nanostructure; Phase transformations; Physics; Scanning electron microscopy; Spark plasma sintering; High entropy alloys; Deformation twinning; Spark plasma sintering; Mechanical alloying; high entropy alloy; Scanning electron microscopy; Nanodefect; Mechanical twin; Aluminium alloy; X ray diffraction; Intergranular fracture; Tensile strength; Metastable phase; Phase transformation; Plasticity; Yield strength; Microstructure; Supersaturated solid solution; Fracture mode
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2012.11.146

► CoNiFeCrAl0.6Ti0.4 high entropy alloy has been synthesized via MA and SPS. ► Deformation twinning possibly occurred during MA or SPS. ► This alloy exhibits excellent mechanical properties. ► The fracture mechanism of this alloy is intergranular fracture and plastic fracture. Inequi-atomic CoNiFeCrAl0.6Ti0.4 high entropy alloy has been designed and fabricated by mechanical alloying (MA) and spark plasma sintering (SPS). Alloying behavior, microstructure, phase evolution and mechanical properties of CoNiFeCrAl0.6Ti0.4 alloy were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscope (TEM), as well as by an Instron testing system. During MA, a supersaturated solid solution consisting of a FCC phase and a metastable BCC phase was formed. Two FCC phases (named FCC1 and FCC2) and a new BCC phase were observed after SPS. During SPS, the metastable BCC phase transformed into the FCC2 phase and the new BCC phase. Meanwhile, the FCC1 phase was the initial FCC phase which was formed during MA. Moreover, nanoscale twins obviously presented only in partial FCC1 phase after SPS. Deformation twinning may be occurred during MA or SPS. The sintered alloy with a high relative density of 98.83% exhibits excellent comprehensive mechanical properties. The yield stress, compressive strength, compression ratio and Vickers hardness of the alloy are 2.08, 2.52GPa, 11.5% and 573 HV, respectively. The fracture mechanism of CoNiFeCrAl0.6Ti0.4 high entropy alloy is mainly performed at intergranular fracture and plastic fracture mode.