液体Ｈｅ温度でのステンレス鋼およびアルミニウム合金の低サイクル疲労特性

Abstract

Axial-strain controlled fatigue tests of stainless steels (SUS 304L, SUS 316L and WM-X) and aluminum alloys (A5083-O and A5356) were conducted at 4K with the strain rate of 0.4%/s and the strain ratio of -1. The fatigue tests at 77 and 300K were also conducted for comparison. The TIG weld metal of stainless steel (WM-X) showed cyclic strain-hardening at 4 and 77K, and cyclic strain-softening at 300K, although other materials showed cyclic strain-hardening at 4, 77 and 300K. It seemed that the strain-induced martensitic transformation influenced the cyclic stress responce of stainless steel. In the fatigue life range of 1000 cycles or more, the fatigue resistance, that means the strain capability at given cycles of fatigue life, of SUS 304L, SUS 316L, WM-X and A5083-O at 4K were nearly equal to or a bit higher than that at 77K. At 4K, the fatigue resistance of SUS 316L was higher than that of SUS 304L, but lied in the middle of a scatter band by a factor of 2 among base metals of stainless steels in literatures. The fatigue resistance of A5083-O was the lowest in a scatter band by a factor of 1.4 among base metals of aluminum alloys in literatures. At 4K, the fatigue resistance of WM-X was almost equivalent to that of SUS 304L and was lower than that of SUS 316L by 20%, being away below that of base metals of stainless steels at 300K. However, the fatigue resistance of the MIG weld metal of aluminum alloy (A5356) was lower than that of A5083-O by 45%, being closer to that of base metals of aluminum alloy at 300K. One must be careful to use the weld metal A5356 at 4K.