Abstract
Nanocrystalline materials structurally stabilized by hard second phases to those materials are usually difficult to make plastic deformation. The application of liquid-enhanced plasticity to those materials is particularly interesting since grain rearrangement by grain boundary diffusion during deformation, which involves sliding and rotation of grains, will be greatly enhanced in nanometer materials as compared with conventional fine-grained materials. In present study, the semi-solid plasticity and diffusion bounding of nanocrystalline Cu-Mg-TiC alloys were investigated. Nanocrystalline Cu-(5 at.%) Mg-(12 vol.%) TiC, Cu-(10 at.%) Mg-(12 vol.%) TiC and Cu-(14 at.%) Mg-(12 vol.%) TiC alloys with grain sizes of about 11 nm, 17 nm and 14 nm were prepared by mechanical alloying, HIP and hot rolling process. The test specimens were prepared from those bulk alloys. Tensile test and diffusion bounding were operated when partial melting occurred. The elongation drastically increased as the melting occurred, and maximum elongations of about 200% were measured at the temperatures where the atomic fractions of the liquid phase were about 0.5. The diffusion bounding at partial melting temperatures also succeeded. After the deformation and bounding, nanocrystalline structures with average grain sizes of about 30 nm were retained.
