ECAP加工された超微細結晶粒ニッケルの繰返し軟化

抄録

Cyclic softening behavior of ultrafine-grained (UFG) nickels was investigated in low-cycle fatigue test. Pure nickel samples were severely deformed by equal channel angular pressing (ECAP) technique to obtain UFG microstructure. In the present study, the maximum number of the ECAP pass was eight. After the ECAP processes, average grain size of the 8-pass sample was refined down to 330nm. The ECAPed samples were shaped to small strip specimens for low-cycle fatigue test. The low-cycle fatigue tests were conducted under a constant plastic strain amplitude, in air at room temperature. During the low-cycle fatigue tests, stress amplitude continuously decreased in all the ECAPed samples, although stress amplitude of an as-annealed sample was almost unchanged. Amount of such cyclic softening depended on the number of ECAP pass and ECAP route: the samples processed by 8-pass ECAP revealed moderated cyclic softening.