Effects of doping Ti3SiC2 with Al on interfacial microstructural evolution, growth kinetics and mechanical properties of Ti3SiC2/TiAl joints

Investigations of the interfacial microstructural evolution, the growth kinetics, and the mechanical properties in the Al-doped joint can derive guidelines for the knowledge-based parameter optimization of dissimilar Ti3SiC2/TiAl joining process. The interfacial microstructural evolution, the growth kinetics of the Ti3SiC2/TiAl joints was greatly altered by doping Ti3SiC2 with Al. The interface in the Ti3(Si0.94Al0.06)C2/TiAl and Ti3(Si0.91Al0.09)C2/TiAl joints changed from γ + α2/TiAl3 + Ti5Si3 + Ti5Si4/Ti3SiC2 to γ + α2/TiAl2/TiAl3 + Ti5Si3 + Ti5Si4/Ti3SiC2, to γ + α2/γ/TiAl2/TiAl3 + Ti5Si3 + Ti5Si4/Ti3SiC2, and to γ + α2/γ/TiAl2/TiAl3 + Ti5Si3 + Ti5Si4/Ti5Si3/Ti3SiC2 as the bonding temperature and duration increased. The growth of the interfacial compound layer in the Ti3(Si0.94Al0.06)C2/TiAl and Ti3(Si0.91Al0.09)C2/TiAl joints followed the cubic law and was controlled by grainboundary diffusion. The Al was the mainly diffusion elements in the Al-doped joints, and its diffusion in the Ti3(Si,Al)C2 substrate and in the interfacial layer was both along the grainboundaries. The bonding activation energies for the Al-doped joints were about 180 kJ/mol, which were much lower than the value (225 kJ/mol) for the undoped Ti3SiC2/TiAl joint. The highest shear strength of the Al-doped joints was about 65 MPa and was about 23% higher than the value of the undoped joint.