速度論的手法とX線回折を用いたJIS ADC12合金の時効進行度の評価

抄録

  Kinetic methods and X-ray non-destructive evaluations are useful in the preparation and evaluation of aging treated specimens. In this study, commercial JIS ADC12 die-cast plates were subjected to aging treatment under conditions of aging temperature ranging between 493 K and 373 K and aging time ranging between 1.2 × 10^-1 ks and 2.2 × 10⁴ ks. Then, the change in hardness increase ΔH was measured by Vickers hardness testing with a test load of 300 gf. At each aging temperature, the relationship between the progress of age hardening, expressed as y ＝ ΔH/ΔH_max (where ΔH_max is the maximum hardness increase), and the aging time was successfully linearized based on the Kolmogorov-Johnson-Mehl-Avrami (KJMA) theory. The temperature dependence of the time to reach the maximum hardness t_m was also successfully linearized by the Arrhenius plot. By applying these kinetic methods, high-temperature short-time aging treatment experiments were performe to estimate the conditions for low-temperature long-time experiments. Furthermore, X-ray diffraction rings were measured by cosα technique where a single incident X-ray exposure is detected using a two-dimensional detector for specimens aged at 493 K. The diffraction rings were observed to confirm the progress of aging. The full width at half maximum of the diffraction rings increased according to the progress of aging and decreased after peak aging. The diffraction angle of the rings shifted to lower values as aging progressed.