抄録
In order to collect the results of micro-fractographic studies of austenitic stainless steel SUS 32 with fractured surfaces fatigued at high temperatures, and to find how far the number of cycles to fatigue failure is dependent on temperature and strain rate, the material was submitted to push-pull low cycle fatigue tests at high temperatures, and observation of the fractured surfaces was carried out by a scanning electron microscope.
For fatigue test conditions the strain rates were set at 40, 4 and 0.4%/min, and the temperatures were set at room temperature, 450°, 600° and 700°C.
The conclusions obtained are as follows;
(1) Striations are observed in each fatigue condition. The striations observed clearly at high temperature are also corresponding to the respective strain cycles.
(2) The striations are bent at twin boundaries.
(3) Under the conditions of 600°C, 0.4%/min and large strain ranges, grain boundary fracture is observed clearly, which is of the same sort as that which is observed on the fracture surface at the creep rupture test made at 600°C.
(4) Uuder the condition of 700°C, grain boundary fracture is also observed, but its surface is not always smooth.
(5) Under the strain rate of 40%/min at 600° and 700°C, striations are observed more easily than grain boundary fracture.
