高速変形特性と材料のミクロ組織

抄録

Mechanical properties at high strain rates were investigated by considering the specific strengthening mechanisms involving the effects of grain size, solid solution and second phase particles. Aluminum and its alloys were tested in tension or compression at strain-rates between 10^-5 and 2000s^-1 at room temperature. The conclusions were as follows:
(1) Aluminum tested at high strain rates could not exhibit strengthening due to grain size refinement according to the well known Hall-Petch equation.
(2) Solutes such as magnesium were able to increase the yield stress of aluminum at high strain rates. The yield stresses at high strain rates for Al-Mg alloys increased with magnesium addition, but the variation in strengthening rate with an additional content of magnesium was almost similar to that at low strain rates.
(3) The treatment of strengthening by the second phase particles was clearly valid to improve the yield stress of Al-Mg-Si alloys at high strain rates. Basically, a decrease in the mean spacing between the second phase particles led the yield stress at high strain rates to be high. It was suggested that an optimum control in distribution of second phase particles was the most valid way for an improvement of the yield stress at high strain rates comparing with other strengthening methods.