Effects of Joining Conditions on Microstructure and Mechanical Properties of Cf/Al Composites and TiAl Alloy Combustion Synthesis Joints

doi:10.1007/s40195-015-0209-9

Abstract

Abstract:

C_f/Al composites and TiAl alloy were joined by combustion synthesis in different joining conditions. Effects of additive Cu, joining temperature and holding time on joint microstructure and shear strength were characterized by employing DTA, SEM, EDS, XRD and shear test. Results show that the additive Cu in the Ti-Al-C interlayer could significantly decrease the reaction temperature owing to the emergence of Al-Cu eutectic liquid. Reaction degree of the interlayer was influenced by joining temperature and holding time. Due to the barrier action of formed TiAl₃ layer, reaction rate of Ti and Al was determined by the atoms diffusion. The reaction between Ti and Al was more sensitive to the joining temperature rather the holding time. The joints shear strength was influenced by joining condition directly. The maximum shear strength of CS joints was 25.89 MPa at 600 °C for 30 min under 5 MPa. Interface evolution mechanism of the CS joint was analyzed based on the experimental results and phase diagram.

Key words: C/Al composite, TiAl alloy, Combustion synthesis, Interface microstructure, Formation mechanism

Guang-Jie Feng, Zhuo-Ran Li, Rui-Hua Liu, Shi-Cheng Feng. Effects of Joining Conditions on Microstructure and Mechanical Properties of C_f/Al Composites and TiAl Alloy Combustion Synthesis Joints[J]. Acta Metallurgica Sinica (English Letters), 2015, 28(4): 405-413.

Figures/Tables 12

Fig. 1 Microstructure of the Cf/Al composites

Fig. 2 Schematic diagram of the joining system

Fig. 3 The schematic of the joint shear test

Fig. 4 DTA curves of the interlayer

Fig. 5 Microstructure of the joint: a the whole joint; b the TiAl side; c the Cf/Al side; d the interlayer

Table 1 EDS compositional analysis results of the different marked regions in Fig. 5d

Region	Al	Cu	Ti	C	Possible phase
A	76.48	-	23.52	-	TiAl₃
B	66.44	33.56	-	-	Al₂Cu
C	-	-	100	-	Ti
D	100	-	-	-	Al
E	76.40	-	23.60	-	TiAl₃
F	38.42	-	-	61.58	Al₄C₃
G	65.69	34.31	-	-	Al₂Cu

Fig. 6 XRD result of the interlayer

Fig. 7 Microstructures of the joints at different joining temperature (t = 30 min): a T = 500 °C; b T = 550 °C; c T = 600 °C; d T = 650 °C

Fig. 8 Microstructures of the joints at different holding time (T = 600 °C): a t = 10 min; b t = 20 min; c t = 30 min; d t = 60 min

Fig. 9 Schematic drawing of formation mechanism of Cf/Al and TiAl CS joint with Ti-Al-C-Cu interlayer: a physical contact; b reaction in the Ti-Al-C-Cu interlayer; c reaction between the interlayer and substrates; d formation of the final joint

Fig. 10 Effects of the joining parameters on the joint shear strength: a joining temperature; b holding time

Fig. 11 Fractograph of the joint at 650 °C for 30 min

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