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Search Publications by: Lawrence Cho (Assoc)

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Displaying 1 - 4 of 4

Characteristics and Mechanisms of Hydrogen-Induced Quasi-Cleavage Fracture of Lath Martensitic Steel

January 10, 2021
Author(s)
Lawrence Cho, Peter E. Bradley, Damian S. Lauria, May L. Martin, Matthew J. Connolly, Jake Benzing, Eun Jung Seo, Kip O. Findley, John G. Speer, Andrew J. Slifka
This study presents an in-depth characterization of the microstructures, crystallographic orientations, and dislocation characteristics beneath the hydrogen-induced quasi-cleavage features of an as-quenched, lath martensitic (') 22MnB5 steel. The fracture

Transgranular Cracking in a Liquid Zn Embrittled High Strength Steel

January 15, 2020
Author(s)
Diptak Bhattacharya, Lawrence Cho, Ellen Van der Aa, Hassan Ghassemi-Armaki, Andreas Pichler, Kip O. Findley, John G. Speer
Intergranular Zn-assisted liquid metal embrittlement (LME) cracks have been frequently reported in steels, involving austenite grain boundary penetration of liquid Zn at high temperature. In the present study, a Zn-coated high strength steel was deformed

Focused Ion Beam-Induced Displacive Phase Transformation From Austenite to Martensite during Fabrication of Quenched and Partitioned Steel Micro-Pillar

January 5, 2020
Author(s)
Eun Jung Seo, Lawrence Cho, Jin Kyung Kim, Javad Mola, Lijia Zhao, Sukjin Lee, Bruno C. De Cooman
We report evidence of displacive phase transformation from retained austenite to martensite during preparation of quenched and partitioned steel micro-pillars by using focused ion beam (FIB) technique. The BCC phase produced by the FIB damage was

Effects of Al-Si Coating and Zn Coating on the Hydrogen Uptake and Embrittlement of Ultra-High Strength Press-Hardened Steel

September 25, 2019
Author(s)
Kyoung Rae Jo, Lawrence Cho, Dimas H. Sulistiyo, Eun Jung Seo, Seong Woo Kim, Bruno C. De Cooman
Press-hardened steel (PHS), used for automotive safety-related structure parts, is sensitive to hydrogen embrittlement due to its martensitic microstructure. Hydrogen is introduced in PHS during the hot press forming (HPF) process, by an atmospheric