Chemical reaction strengthening of Al/TiC metal matrix composites by isothermal heat treatment at 913 K

The effect of solid state heat treatment at 913 K on extruded XD Al/TiC metal matrix composite with 0.7 and 4.0 μm particle sizes has been investigated. The interfaces between Al and TiC after extrusion were atomically abrupt, as observed by HRTEM. On holding at 913 K, the composite with submicron particle size showed substantial changes in the phases present due to reaction between Al and TiC at 913 K. The stable reaction products are Al₃Ti and Al₄C₃. A substantial increase in Young's modulus occurs. The room and elevated temperature strength and hardness of the composite with submicron particles also increase significantly with time of heat treatment, but at the expense of ductility. The effect of heat treatment over the time range investigated is limited to the interfaces for the 4.0 μm TiC particle size composite due to longer diffusion paths.