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In the present work, the phase equilibria of the Ni-Ga-Cr ternary system at 850, 1000 and 1150 °C were experimentally investigated to provide the essential data for developing the high-entropy shape memory alloys (HESMAs) containing Ni, Ga and Cr. At 850 °C, in the Ni-rich portion, the B2 phase shows equilibrium with the L12 phase when the Cr content is less than 10.49 at. %, while displaying the equilibrium with L12 and BCC phases when the Cr content increases. The B2 + L12 + BCC changes into B2 + FCC + BCC three-phase equilibria from 850 to 1150 °C, as the L12 phase region becomes narrow with rising temperature. The two-phase equilibrium, B2 + BCC, was found at all the isothermal sections investigated. Other three-phase equilibria were also discovered: B2 + α-Cr3Ga + BCC and Ni2Ga3 + α-Cr3Ga + L at 850 °C, and B2 + α-Cr3Ga + L at 1000 °C. Significantly, an athermal ω intermetallic compound with the space group of P3¯m1 was observed distributing at the B2 phase in the quenched Ni45.98-Ga25.50-Cr28.52, Ni42.23-Ga15.70-Cr42.07 and Ni16.54-Ga13.63-Cr69.83 (at. %) alloys after being annealed at 1150 °C for 10 days. The high-resolution transmission electron microscopy (HRTEM) results reveal that the ω shows a crystallographic orientation of [11¯0]B2//[112¯0]ω; (111)B2//(0001)ω with the B2 parent phase.

This study presents the criteria for shape control in the micro-pulling-down (μ-PD) method for low-wettability systems (dewetting μ-PD method), which enables us to achieve highly shape-controllable crystal growth. In the dewetting μ-PD method, the presence of the die wall inhibits the direct observation of the meniscus during the process. Therefore, in this study, the meniscus shape was calculated using the Young-Laplace equation to predict the optimal crystal growth conditions. The free-end and fixed-end boundary conditions to be satisfied for the differential equations were defined at the triple point, with the melt on the die wall. The relationship between the crystal diameter and pressure in the fixed-end condition, wherein the wetting angle (α) at the triple point of the crystal was 90°, indicated the suppression of the melt infiltration by the presence of crystals. The gap between the die and crystal was minimized for the contact angle (θ) and growth angle (α gr ) in the fixed-end and free-end conditions, at which |α gr + θ - π| was minimum at a given pressure under the assumption of single-valued solutions. The results of this study will facilitate the formation of noble-metal alloys with a net shape and expand the scope for the development of new materials., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)