Mohammad Hamisi - Department of mechanical engineering, Shahid Beheshti University
Seyed Ebrahim Moussavi Torshizi - Department of mechanical engineering, Shahid Beheshti University

In this investigation, a precipitation hardenable austenite stainless steel was subjected to different heat treatment cycles to study their influence on the microstructure and properties. The purpose of this article is to study the effect of structural changes on natural frequencies and damping coefficients of samples of AISI 321 stainless steel. Sigma phase precipitation nucleates at the grain boundaries and becomes more intense with the increase of time and temperature. Sigma phase and chromium carbides cause severe sensitization in specimens aged at 750 °C, 850 °C and 950 °C for 72 hours. With increasing structural changes, it was found that the natural frequencies of the five modulus increase significantly. Mechanical properties were evaluated at room temperature for all the heattreatedsamples. A reasonable increase in elasticity modulus was observed after aging. These promising results are the elaboration of a nondestructive new method for estimating the remaining life for components of different generations under long-term overheated operation conditions.

Aging, AISI 321, Damping Capacity, Microstructural change, Mechanical properties