Preparation and Mechanical Property of the Ceramic-reinforced Cr0.5MoNbWTi Refractory High-entropy Alloy Matrix Composites

doi:10.15541/jim20200479

Abstract

Abstract:

As promising high-temperature structural materials, refractory high-entropy alloys have widely applications due to their excellent mechanical properties, high-temperature stability and oxidation resistance. For further improving the mechanical properties, ceramic-reinforced refractory high-entropy alloy matrix composites were prepared by utilizing in-situ reaction sintering. The supersaturated body centered cubic (BCC) solid solution of Cr_0.5MoNbWTi doped with nonmetallic elements of carbon, nitrogen and oxygen was prepared by mechanical alloying. During spark plasma sintering, (Nb,Ti)(N,C) and Ti₂O₃ceramic reinforcements were formed by in-situ reaction between nonmetallic and metallic elements. The ceramic reinforcements were well dispersed in BCC matrix. The formation mechanism and the strengthening effects of the ceramic reinforcements were discussed in this paper. With the assistance of the fine-grained ceramic reinforcements, the composites exhibited ultra-high ambient-temperature strength (4033 MPa), ambient-temperature hardness (11.57 GPa), and superior high-temperature yield strength (572 MPa at 1400 ℃).

Key words: refractory high-entropy alloy, ceramic reinforcement, composite, mechanical property

CLC Number:

TQ174
TF125

LÜ Shasha, ZU Yufei, CHEN Guoqing, ZHAO Bojun, FU Xuesong, ZHOU Wenlong. Preparation and Mechanical Property of the Ceramic-reinforced Cr_0.5MoNbWTi Refractory High-entropy Alloy Matrix Composites[J]. Journal of Inorganic Materials, 2021, 36(4): 386-392.

Figures/Tables 9

Fig. 1 XRD patterns of the powders mechanically milled for different time

Table 1 Concentrations of C, N, and O in the raw powders and as-milled powders

Sample	C/wt%	O/wt%	N/wt%
Mixture before ball milling	0.044	0.448	0.046
Mixture after ball milling	0.482	2.181	3.920

Fig. 2 SEM images of the ceramic-reinforced refractory high-entropy alloys matrix composite (a) Low magnification; (b) High magnification

Fig. 3 XRD pattern of the as-sintered composite

Fig. 4 Backscattered electron SEM image (a) and the corresponding EPMA mappings (b-i) of the alloying components in the composite

Table 2 Chemical compositions (at%) of the phases in the as-sintered composite

	Cr	Mo	Nb	W	Ti	Fe	C	O	N
BCC	15.25	34.17	8.21	37.15	0.58	4.25	0.39	0	0
(Nb,Ti) (N,C)	1.38	0.39	31.73	0.03	18.37	0.12	9.95	4.51	33.52
Ti₂O₃	1.18	0.81	1.32	0.71	35.14	0.21	0.96	59.66	0.01

Table 3 Enthalpy of mixing and electronegativity difference between nonmetallic elements and metallic elements

Enthalpy of mixing/(kJ·mol^-1)/Electronegativity difference	Cr	Mo	Nb	W	Ti
C*	-61/0.89	-67/0.39	-102/0.95	-60/0.85	-109/1.01
N*	-107/1.38	-115/0.88	-174/1.44	-103/1.34	-190/1.50
O**	-205/1.78	-174/1.28	-307/1.84	-164/1.74	-327/1.90

Fig. 5 Gibbs free energies of the reactions between the nonmetallic and metallic elements as a function of temperature

Fig. 6 Engineering stress-strain curves of the composite at room temperature and 1400 ℃ (a); Comparison of mechanical properties of the typical refractory HEAs (b)

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