Creep Properties and Damage Mechanisms of 2D-SiCf/SiC Composites Prepared by CVI

doi:10.15541/jim20190450

Abstract

Abstract:

The creep properties of 2D-SiC_f/SiC composites prepared by chemical vapor infiltration were studied. The creep temperatures were 1200, 1300 and 1400 ℃, and the stress levels ranged from 100 MPa to 140 MPa. Scanning electron microscope was used to observe the fracture morphology, and their microstructure was analyzed by high resolution transmission electron microscope. The results show that the creep damage modes of 2D-SiC_f/SiC composites mainly include the generation of matrix crack, interfacial debonding and fiber creep. The creep of bridging fibers leads to increase of the opening distance of the matrix cracks and further creep rupture of the composite. The microstructural stability of the SiC fiber plays a critical role in the creep properties of 2D-SiC_f/SiC composites. SiC grains in the fibers of 2D-SiC_f/SiC composites do not grow when it is crept at 1200 ℃/100 MPa. However, the grains grow significantly when the creep temperature increases to 1400 ℃. The creep rupture time decreases to 8.6 h from above 200 h, and the steady-state creep rate increases by three orders of magnitude.

Key words: 2D-SiC_f/SiC composite, creep properties, creep damage, SiC fiber

CLC Number:

TQ174

WANG Xi,WANG Kejie,BAI Hui,SONG Zhuolin,WANG Bo,ZHANG Chengyu. Creep Properties and Damage Mechanisms of 2D-SiC_f/SiC Composites Prepared by CVI[J]. Journal of Inorganic Materials, 2020, 35(7): 817-821.

Figures/Tables 11

Table 1 Properties of the SiC fiber

Diameter/μm	Density/(g?cm^-3)	Tensile strength/GPa	Tensile modulus/GPa
14	2.74	2.7	270

Table 2 Properties of the SiCf/SiC composite

Density/(g?cm^-3)	Tensile strength/MPa	Tensile modulus/GPa	Porosity/%
2.5	225	220	~23

Fig. 1 Shape and dimensions for creep specimen of 2D-SiCf/ SiC composites

Fig. 2 Creep curves at 1200 ℃ under different stresses for 2D-SiCf/SiC composites

Table 3 Creep properties of 2D-SiCf/SiC composites

Temperature/ ℃	Stress/ MPa	Rupture time/h	Steady-state creep strain rate/s^-1
1200	100	216.0	6.1′10^-9
1200	120	89.0	2.2′10^-8
1200	140	50.0	4.5′10^-8
1300	100	121.0	4.4′10^-8
1300	120	53.0	4.9′10^-8
1300	140	22.0	2.0′10^-7
1400	100	8.6	1.5′10^-6

Fig. 3 Fracture morphologies of 2D-SiCf/SiC composites at different creep conditions (a) 1200 ℃/100 MPa; (b) 1200 ℃/120 MPa; (c) 1200 ℃/140 MPa; (d) 1300 ℃/100 MPa;(e) 1400 ℃/100 MPa

Fig. 4 Crack image of creep specimen at 1200 ℃/100 MPa

Fig. 5 Relationship between steady state creep strain rate and stress σ, temperature T (a) Steady-state creep strain rate versus stress; (b) Steady-state creep strain rate vs temperature

Fig. 6 TEM images of as-received 2D-SiCf/SiC composite (a) Bright image; (b) HRTEM and SAED of SiC fiber

Fig. 7 HRTEM and SAED images of SiC fiber in crept 2D-SiCf/SiC composites (a) 1200 ℃/100 MPa; (b) 1400 ℃/100 MPa

Fig. 8 Grain size distributions of SiC fibers in 2D-SiCf/SiC composites at different creep conditions

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