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The Defining Role of Micro-fissures on the Mechanical Behavior of Laser-Welded Fully Austenitic Stainless Steel
Journal
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
ISSN
10735623
Date Issued
2022-06-01
Author(s)
Sarkar, Arnab
Basu, Soudip
Pattnaik, Amulya Bihari
Jaya, Balila Nagamani
Karagadde, Shyamprasad
Samajdar, Indradev
Kumar, Hemant
Kumar, Ravi
Mythili, R.
Ghosh, Chanchal
Dasgupta, Arup
Albert, Shaju
Abstract
Laser-welded fully austenitic stainless steel (AISI 316LN) weldments revealed the presence of micro-fissures. They appeared at the grain boundaries, near the center of the welds. The grain boundaries, however, did not contain second phase or micro-segregation. The relative presence of micro-fissures decreased with increasing weld heat input. Spatial locations of the micro-fissures and their relative presence were associated with local misorientations and, in particular, with grain reference orientation deviation. Microstructural and microtextural studies indicated that solidification shrinkage was the origin of the micro-fissures in the laser welds. The use of sub-size tensile specimens (of 5- and 1-mm gauge length) with digital image correlation (DIC) related the presence of micro-fissures with mechanical property degradation by the appearance of strain localizations. This was further confirmed by analytical solutions and finite element analysis of critical flaw size and critical stress for fracture.