Structure and hardness of B2 ordered refractory AlNbTiVZr0.5 high entropy alloy after high-pressure torsion

Abstract

High-pressure torsion (HPT) at room temperature was applied to an AlNbTiVZr 0.5 refractory high entropy alloy. In the initial as-cast condition the alloy was composed of a coarse-grained B2 matrix phase and a continuous network of C14 Laves phase particles with the volume fraction of 19%. HPT resulted in the formation of a nanocrystalline structure in the B2 matrix with an average size of grains/subgrains of 25 nm after 5 revolutions. The B2 phase also underwent significant disordering during HPT. The Laves phase network was broken and individual particles became much thinner in comparison with those in the initial condition. Microhardness measurements have revealed typical of HPT gradient along the radius which decreased with increasing the number of revolutions. It was also found that the nanohardness of the B2 phase increased after HPT while the nanohardness of the Laves phase decreased. A strong decrease in the Young's modulus of the B2 phase was also found. Factors governing structure and properties evolution of the alloy during HPT were discussed.

Microstructure evolution of a novel low-density Ti–Cr–Nb–V refractory high entropy alloy during cold rolling and subsequent annealing

“…Therefore, the lattice distortion is not expected to be high in any possible atomic pair. However, the shear modulus of Cr (110 GPa) is noticeably higher than that for the other elements (38)(39)(40)(41)(42)(43)(44)(45)(46)(47). Therefore, strong modulus distortions are expected around Cr atoms that can generate the strongest solid solution strengthening.…”

“…This approach has been used extensively for HEAs based on late 3d transition metals [28][29][30][31][32][33][34][35], but not often applied to RHEAs/RCCAs [36]. In this work, microstructure and microhardness evolution during cold rolling and subsequent annealing at 800-1200°C of a new non-equiatomic Ti-Cr-Nb-V (Ti 1.89 CrNbV 0.56 ) RHEA, developed on the basis of earlier results on the Al-Cr-Nb-Ti-V-Zr system RHEAs/RCCAs [7,8,13,[37][38][39][40][41][42][43], are studied in details.…”

Structures and mechanical properties of Ti-Nb-Cr-V-Ni-Al refractory high entropy alloys

“…The B2 phase is often observed in alloys with Al [19][20][21][22][23]. Some alloys were revealed to have a single B2 phase structure [20,23,24], sometimes containing a small amount of non-coherent secondary phases like a Laves phase, σ-phase or Zr aluminides [25,26]. However the most attractive option is probably associated with the production of a mixture of the bcc þ B2 coherent phases.…”

Metastability in high-entropy alloys: A review

“…An abundance of investigations have emerged in the literature focusing on microstructural characteristics, defect evolution as well as mechanical properties for HEAs after SPD. [99][100][101][102][103][104][105][106][107][108][109] A recent work by Bhattacharjee et al 106 reported that the nanolamellar AlCoCrFeNi 2.1 HEA, which was achieved by cryorolling and annealing processes, exhibited a remarkable increase in both the yield strength and the ultimate tensile strength (UTS) without sacrificing too much ductility [ Fig. 8(a)].…”