Evolution of Mechanical Properties of Mini-SiCf/SiC Composites at High Temperatures over a Long Period of Time

doi:10.15541/jim20250031

Abstract

Abstract:

Continuous silicon carbide fiber reinforced silicon carbide (SiC_f/SiC) composites are widely utilized in the hot-end components of aero engines due to their exceptional properties and high-temperature resistance. To ensure the safety and reliability of SiC_f/SiC composite parts during service, it is crucial to investigate the evolution of their mechanical properties under prolonged high-temperature exposure. In this study, mini-SiC_f/SiC composites with a BN interface were fabricated using Cansas-II SiC fibers. These mini-SiC_f/SiC composites underwent heat treatment at 1100, 1200, and 1350 ℃ for durations of 5, 10, 50, 100, and 200 h, respectively, to examine the effects of high-temperature and long-term heat treatment on their mechanical properties and microstructure. The results show that at 1100 ℃, heat treatment has no significant impact on the mini-SiC_f/SiC composites. The mechanical properties remain largely unchanged, and the contribution fractions of each stage to the overall mechanical performance remain consistent. At 1200 ℃, short-term heat treatment shows minimal effects on the mini-SiC_f/SiC composites without notable change in tensile strength. However, prolonged heat treatment leads to damage in the SiC fibers, thereby decreasing their tensile strength. At 1350 ℃, heat treatment significantly improves the properties of the BN interface but causes severe damage to the SiC fibers, resulting in a marked decline in the mechanical properties of the mini composites. As the heat treatment duration increases, the extent of fiber damage intensifies, leading to a continuous deterioration in the mechanical performance of the composites.

Key words: Cansas-II SiC fiber, mini-SiC_f/SiC composite, heat treatment, acoustic emission, saturated matrix crack spacing

CLC Number:

TB332

CHEN Bin, REN Ke, WANG Yiguang. Evolution of Mechanical Properties of Mini-SiC_f/SiC Composites at High Temperatures over a Long Period of Time[J]. Journal of Inorganic Materials, 2025, 40(9): 971-980.

Figures/Tables 11

Table 1 General properties of Cansas-II SiC fibers

Fiber	Diameter/ μm	C/Si	Oxygen/ % (in atom)	Density/ (g·cm^-3)	Linear density/(g·m^-1)
Cansas-Ⅱ	13±1	1.61	<0.8	2.7±0.1	0.2

Fig. 1 Schematic diagram of tensile test of mini-SiCf/SiC composites

Fig. 2 Cross-sectional morphologies and EDS analyses of mini-SiCf/SiC composites (a) Low magnification; (b) High magnification; (c) EDS results of white square marked in (a); (d) Line scan results of red line shown in (b) Colorful figures are available on website

Fig. 3 Stress-strain curves of mini-SiCf/SiC composites after heat treatment at 1100 (a), 1200 (b), and 1350 ℃ (c) for different periods Colorful figures are available on website

Fig. 4 Tensile stress-strain curves and acoustic emission test results of mini-SiCf/SiC composites after heat treatment at 1100 (A), 1200 (B), and 1350 ℃ (C) for different periods, change trend of the stress of each stage and the contribution fraction of each stage (a-e) Tensile stress-strain curves and acoustic emission test results for 5 (a), 10 (b), 50 (c), 100 (d), and 200 h (e); (f) Change trend of the stress of each stage; (g) Contribution fraction of each stage. Colorful figures are available on website

Fig. 5 Morphologies of matrix fracture and fiber pull-out of mini-SiCf/SiC composites after heat treatment at 1100 (A), 1200 (B), 1350 ℃ (C) for different periods (a, f) 5 h; (b, g) 10 h; (c, h) 50 h; (d, i) 100 h; (e, j) 200 h

Table 2 SMCS after tensile test of mini-SiCf/SiC composites after heat treatment at 1100 ℃ for different periods

HT time/h	SMCS/μm
5	254±12
10	247±15
50	253±13
100	246±12
200	248±17

Table 3 SMCS after tensile test of mini-SiCf/SiC composites after heat treatment at 1200 ℃ for different periods

HT time/h	SMCS/μm
5	243±16
10	239±15
50	231±18
100	197±16
200	184±13

Table 4 SMCS after tensile test of mini-SiCf/SiC composites after heat treatment at 1350 ℃ for different periods

HT time/h	SMCS/μm
5	187±20
10	176±15
50	159±17
100	146±13
200	138±12

Fig. 6 Weibull distributions of tensile strengths of mini-SiCf/SiC composites after heat treatment at different temperature (a) Untreated specimen; (b) 1100 ℃; (c) 1200 ℃; (d) 1350 ℃

Table 5 Weibull modulus (m) of distributions of different mini-SiCf/SiC composites after tensile test

HT time/h	m
HT time/h	1100 ℃	1200 ℃	1350 ℃
5	15.11	16.06	9.51
10	11.92	23.45	18.75
50	12.14	9.67	11.38
100	13.39	12.14	19.87
200	20.78	7.28	20.41

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