Ａｌ‐３％Ｆｅ‐３％Ｎｉ‐３％Ｃｒ‐０．７％Ｚｒ Ｐ／Ｍ合金のメカニカルグラインデング処理による高強度化

Abstract

Mechanical grinding (MG) of air atomized Al–3Fe–3Ni–3Cr–0.7Zr (in mass%) alloy powder was performed with a vibrational ball mill for various times up to 154.8 ks in an argon atmosphere. Subsequently, MG powders as well as atomized powder were hot extruded to rectangular bar shapes (20 mm in width and 3.5 mm in thickness) at 673 K. The effect of MG time on the mechanical properties of extrudates up to 673 K and on the microstructures of MG powders and extrudates was investigated. Vickers hardness of MG powders increased to about 300 with increasing of MG time up to about 30 ks. The results of DSC, XRD and TEM revealed that the primary intermetallic compounds in atomized powder were finely ground and dispersed by MG. The results also suggest that elements consisting of the compounds were dissolved in the matrix beyond their equilibrium solubility by prolongation of MG time. MG and subsequent hot extrusion processes at 673 K resulted in giving extremely fine sub-grains. On boundaries or interior of the sub-grains, the transition elements dissolved in the matrix by MA were precipitated finely as Al3Fe, Al3Ni and Al13Cr2 phase particles. The tensile strength at ambient temperature and at 573 K were about 431.9 MPa and 208.7 MPa for extrusion specimen from atomized powder, and 675.7 MPa and 281 MPa for extrusion specimen from 154.8 ks-MG powder, respectively. However, the ductility was poor in MG materials. Improvements in the mechanical strength are mainly attributed to the presence of extremely fine sub-structure and finely dispersed particles which were introduced during MG and extrusion process.