Cyclic Strain Rate Dependent Low-Cycle Fatigue Behavior of Alloy 617

Abstract

Alloy 617 is identified as a potential material for defense applications, particularly in military air platforms. Therefore, this study aims to examine the impact of strain rate on Alloy 617 properties during low-cycle fatigue (LCF) at room temperature (RT). LCF life properties and damage mechanism of alloy 617 are examined across a strain rate range of (5x10-4 ~ 10-2 s-1) in a fully-reversed controlled total strain range of 1.2%. Slow strain rate test (SSRT) is found to be a cost-effective method for assessing the material capability to respond to environmental interference. This study shows that LCF life of Alloy 617 is strongly influenced by the time-dependent mechanism, in terms of SSRT. The relationship between total strain, plastic strain, and time to failure with strain rates are established and expressed using the power law function to describe the fatigue life. Fractured specimens undergo metallography examination using an electron microscope, and fractography is discussed to differentiate the impact of SSRT on the physical damage characteristics under LCF loadings. LCF resistance of Alloy 617 is found to be time-dependent. Based on the results, it is recommended that the factor of safety must be considered in the designing phase to evaluate the fatigue life.

Keywords

• alloy 617
• fatigue life
• fractography
• low-cycle fatigue
• slow strain rate test