Mechanical Properties Estimation of Materials With Different Grain Sizes by Small Punch Test at Elevated Temperature

As an effective method for performance analysis of in-service component, small punch test (SPT) can be used in various situations to analyze material characterization of structural component. In order to improve stress distribution and fatigue strength of materials, ultrasonic impact treatment (UIT) has been widely researched in recent years. However, the nanocrystalline layer is so thin that can not be analyzed by the conventional tests. In this paper, the mechanical properties of AISI304 which were improved by ultrasonic impact treatment were evaluated by small punch test. Meanwhile, as two important factors, the temperature and grain size were considered. The influence of impact time on surface treatment of AISI304 was analyzed. It can be found that the grain size decreases with the increase of impact time. Based on the variation of Load-Displacement (L-D) curves obtained by small punch test, the strengths of treated specimens were obtained. Finally, the mechanical property evolutions with different surface grain sizes were discussed at elevated temperature.