Papers by Keyword: Aging Hardening

Abstract: By transmission electron microscopy (TEM) and optical microscopy (OM), the isochronal aging hardening law and microstructure have been studied for the Mg-8Gd-3Y-0.5Zr alloy after cold rolling. During isochronal aging process (heated from room temperature to 500 with the heating rate of 1/min), there are two peak hardness temperature points, which are corresponding to the large number of precipitation of β and β phases, and the peak aging time of the alloy substantially decreased with the increase of deformation reduction. The β phases started to precipitate at temperatures of 145, 134, 127 and 124 in the alloy after cold rolling with the reduction of 0%, 8%, 15% and 22%. The heating rate greatly affected the starting precipitation of metastable phases. β phases started to precipitate at temperatures of 109 and 124 with the reduction of 22% and with the heating rates of 3 /min and 30 /min.

Abstract: By the aid of optical microscope, Hardness measurement, SEM, TEM and the chemical quantitative phase analysis technique, the influence of copper, niobium, and chromium on the aging hardness has been investigated. The aging precipitation behavior and the interaction between various precipitates have also been discussed. The results indicate that since there are multi aging-hardening elements in the steel the aging hardening behaviors are complicated. During the aging the ε－copper， and carbides containing iron and chromium will precipitate. Also, new niobium carbonitride precipitation occurs. These precipitation processes cause marked hardening effect and various hardness peaks. The ε－copper can precipitate at dislocation and lath boundaries preferentially. During the aging the bainite lath united and became wider and then gradually vanished.