A treatment process for a composite comprising a matrix of a precipitation hardenable aluminum alloy and a particulate or short fiber ceramic reinforcement. The process includes hot and/or cold working the composite, subjecting the composite to a controlled heating step in which the composite is raised from ambient temperature to a temperature of from 250 to 450.degree. C. at a rate of temperature increase less than 1000.degree. C. per hour, and subjecting the resulting heat treated composite to a solution treating step.