Plastic flow and fracture behavior of an Al-Ti-Cu nanocomposite

Isothermal compression tests were conducted on an Al-Ti-Cu nanocomposite. From this work, the following conclusions can be drawn: The stress-strain curves and values of the strain-rate sensitivity of the flow stress (m) at ambient and slightly elevated temperatures are typical of microcrystalline aluminum alloys whose deformation is controlled by the competition between dislocation multiplication and dynamic recovery. For the most part, the flow curves showed steady-state flow following a short strain-hardening transient; m values were between 0.04-0.16. These values of m are much lower than those typically associated with boundary-sliding processes (i.e., m=0.5-1.0). The nanophase Al-Ti-Cu alloy exhibited a brittle-to-ductile transition behavior as a function of temperature and strain rate. Brittle behavior occurred at a critical stress level and appeared to require the initiation of plastic flow. An Arrhenius analysis of the fracture data yielded an activation energy of 98.7 kJ/mol or a value between that of bulk and boundary diffusion.