Microstructure and mechanical properties of Ti3SiC2/Ti3SiC2 diffusion bonded joints using Ti foil as an interlayer

Diffusion bonded joints of Ti3SiC2 ceramic without or with a Ti foil were fabricated. The effects of temperature, holding time and Ti foil thickness on the microstructural evolution and mechanical properties of Ti3SiC2/Ti/Ti3SiC2 joints were systematically investigated. Compared with the case of direct diffusion joints, the Ti3SiC2/Ti/Ti3SiC2 joint was obtained at 1000 degrees C and the bonding temperature reduced by 150 degrees C. The typical microstructure of the Ti3SiC2/Ti/Ti3SiC2 joints obtained at 1100 degrees C with a 60-mu m thick Ti foil for 60 min consisted of Ti3SiC2/Ti(5)Si(3)c/TiSi/Ti5Si4/TiAl2/TiAl/ Ti3Al/alpha-Ti/Ti3Al/TiAl/TiAl2/Ti5Si4/TiSi/Ti5Si3Cx/Ti3SiC2 layers in that order. The formation sequence of the diffusion layer at the joint was TiAl2 -> TiSi -> Ti5Si3 -> Ti5Si4 -> TiAl -> Ti3Al. Upon changing the bonding temperature from 1000 to 1150 degrees C, the thickness of the Ti foil from 0 to 120 mu m and the holding time from 30 to 120 min, the shear strength first increased and then decreased. The shear strength of the Ti3SiC2/Ti/Ti3SiC2 joint at 1100 degrees C for 60 min under 20 MPa reached 174 +/- 4 MPa, which was 1.87 times that of the direct diffusion joint under the same experimental conditions. The results of Vickers microhardness measurements showed that the Ti5Si4 and TiSi compounds exhibited the highest microhardness of 853 43HV. The fractures caused by Ti(5S)i(4) and TiSi propagated into the Ti5Si3Cx, Ti3SiC2 and Ti-Al diffusion layers.