TY - JOUR
T1 - Solid Solutions with bcc, hcp, and fcc Structures Formed in a Composition Line in Multicomponent Ir–Rh–Ru–W–Mo System
AU - Takeuchi, Akira
AU - Wada, Takeshi
AU - Kato, Hidemi
N1 - Funding Information:
This work was supported by JSPS KAKENHI Grant Number JP17H03375.
Publisher Copyright:
©2019 The Japan Institute of Metals and Materials
PY - 2019
Y1 - 2019
N2 - Five IrRhRuWMo alloys selected based on alloy design with valence electron concentration (VEC) were examined for their formation of single, dual, and triple phases of bcc, fcc, and hcp structures. These structures were predicted with Thermo-Calc 2019a and the TCHEA3 database on a cross-sectional phase diagram along a composition line: Ir0.415254(100 1 2x)Rh0.415254(100 1 2x)Ru0.169492(100 1 2x)WxMox (x: 050 at%). At T = 2100 K, four types of phases were predicted: (1) a single bcc, fcc, and hcp phase, respectively, at x = 35 (Alloy A, VEC = 6.849), 15 (Alloy C, VEC = 7.981), and 5 (Alloy E, VEC = 8.574); (2) a mixture of bcc+hcp and hcp+fcc at x = 24 (Alloy B, VEC = 7.472) and 8 (Alloy D, VEC = 8.378), respectively; (3) a triple mixture of bcc+hcp+fcc; and (4) a mixture of bcc+fcc in Alloys AE at low temperature. Experiments at 2100 K revealed that Alloys CE tended to exhibit better reproducibility and that Alloy E can be regarded as a new refractory high-entropy alloy (HEA) with fcc structure. Alloy C annealed at T = 1273 K for 200 h maintained a single-hcp structure. The non-appearance of thermodynamically stable phases at low temperature in the IrRhRuWMo system was analogically explained as slow diffusion. The VEC analysis for HEAs with hcp structures was extended by including the range of 7.5 ¯ VEC ¯ 8.4 for alloys consisting of 4d and 5d transition metals annealed near their solidus temperature. The IrRhRuWMo system was significant in providing all possible simple solid solutions of bcc, hcp, and fcc phases.
AB - Five IrRhRuWMo alloys selected based on alloy design with valence electron concentration (VEC) were examined for their formation of single, dual, and triple phases of bcc, fcc, and hcp structures. These structures were predicted with Thermo-Calc 2019a and the TCHEA3 database on a cross-sectional phase diagram along a composition line: Ir0.415254(100 1 2x)Rh0.415254(100 1 2x)Ru0.169492(100 1 2x)WxMox (x: 050 at%). At T = 2100 K, four types of phases were predicted: (1) a single bcc, fcc, and hcp phase, respectively, at x = 35 (Alloy A, VEC = 6.849), 15 (Alloy C, VEC = 7.981), and 5 (Alloy E, VEC = 8.574); (2) a mixture of bcc+hcp and hcp+fcc at x = 24 (Alloy B, VEC = 7.472) and 8 (Alloy D, VEC = 8.378), respectively; (3) a triple mixture of bcc+hcp+fcc; and (4) a mixture of bcc+fcc in Alloys AE at low temperature. Experiments at 2100 K revealed that Alloys CE tended to exhibit better reproducibility and that Alloy E can be regarded as a new refractory high-entropy alloy (HEA) with fcc structure. Alloy C annealed at T = 1273 K for 200 h maintained a single-hcp structure. The non-appearance of thermodynamically stable phases at low temperature in the IrRhRuWMo system was analogically explained as slow diffusion. The VEC analysis for HEAs with hcp structures was extended by including the range of 7.5 ¯ VEC ¯ 8.4 for alloys consisting of 4d and 5d transition metals annealed near their solidus temperature. The IrRhRuWMo system was significant in providing all possible simple solid solutions of bcc, hcp, and fcc phases.
KW - High-entropy alloys
KW - Solid solutions
KW - Transition metals
KW - Valence electron concentration
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U2 - 10.2320/matertrans.MT-M2019212
DO - 10.2320/matertrans.MT-M2019212
M3 - Article
AN - SCOPUS:85074211238
VL - 60
SP - 2267
EP - 2276
JO - Materials Transactions
JF - Materials Transactions
SN - 1345-9678
IS - 11
ER -