Microstructure-crystallographic texture and substructure evolution in unpeened and laser shock peened HSLA steel upon ratcheting deformation

ABSTRACT

Uniaxial ratcheting behaviours associated with microstructural development of unpeened and laser shock peened ASTM A 588 Grade D High Strength Low Alloy (HSLA) steel were studied in this investigation. The mechanism of plastic deformation and crystallographic texture evolution during ratcheting was also studied. For this, the primary experimental works involved were stress-controlled ratcheting fatigue tests (on unpeened/laser-peened specimens) at room temperature. Followed by this, microstructure and texture evolution on the surfaces and/or cross sections of the deformed specimens, using electron back scattered diffraction (EBSD) were studied in detail. Additionally, the substructural evolution of some selected samples was also studied using transmission electron microscopy (TEM). The results indicated that the average grain size of all the unpeened ratcheted specimens was marginally reduced after fatigue tests. The laser-peened specimen, however, showed a marginal increase in average grain size after ratcheting. Continuous dynamic recovery and recrystallisation (CDRR) during ratcheting was thought to be the cause of the observed reduction in average grain size in unpeened specimens, whereas continuous dynamic recrystallisation (CDRX) was believed to be the controlling factor for marginal accretion of grain size in laser-peened specimens. The plastic deformation of investigated steel was qualitatively explained by the observed dislocation patterns and their evolution.

KEYWORDS:

• HSLA steel
• ratcheting behaviour
• plastic deformation
• EBSD
• microstructure-crystallographic texture
• substructure evolution

Acknowledgements

The authors are grateful to Dr. Arun Kumar Rai RRCAT Indore for helping us to conduct the laser shock peening experiment in his laboratory. The authors are thankful to Dr. P. Ganesh RRCAT Indore for his encouragement and support during the course of this work. The authors are also thankful to Prof. I. Samajdar for conducting EBSD and TEM studies of the samples in his laboratory, at the Dept. of Metallurgical Engg. and Materials Science, IIT Bombay, Powai, Mumbai. Pushpendra Kumar Dwivedi: Conceptualisation, Methodology, Visualisation, Investigation, Software, Writing-Original draft preparation. R. Vinjamuri: Software, Writing-Reviewing and Editing. Krishna Dutta: Supervision, Writing-Reviewing and Editing.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The raw/processed data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study.