Work hardening behavior of Ti/Al-based metal intermetallic laminates

Titanium- and aluminum-based in situ metal intermetallic laminate (MIL) composites were prepared by solid-state diffusion bonding. The transition joints between Ti/Al were made at temperatures 550 and 575 °C with different bonding time under uniaxial pressure of 4 MPa under high vacuum to achieve MILs with different volume fraction of intermetallic phase. The phase and elemental analyses revealed the presence of only TiAl3 intermetallic layer formed between Ti/Al diffusion couple. Also, the layer thickness of the intermetallic phase increased with the increase in both bonding time and temperature. Compression tests were conducted on these MILs at room temperature both parallel and perpendicular to intermetallic layers. The mechanical properties and the failure mode of these MILs were studied based on the volume fraction of intermetallic phase. Results showed that the strength along the parallel direction of the MILs were much higher than the perpendicular direction. The failure mechanism of the MILs also varied based on the volume fraction of the intermetallic phases. Fractography revealed that with high intermetallic content, cracks were formed only on the intermetallic layer irrespective of loading direction. MILs containing intermetallic phase fraction exhibited better work hardening rate and the hardening rate behavior varied with the loading orientation.