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Description
Martensitic advanced high strength steel (MS-AHSS), specifically MS1500, is an identified steel for various applications in the automotive industry to reduce the car weight improving fuel economy without compromising structural integrity. Nevertheless, hydrogen embrittlement (HE) is an issue with MS-AHSS. The HE susceptibility is affected by a number of the steel’s characteristics including the strength of the material, microstructure, tempering temperature, and precipitates. While the microstructure of MS1500 is considered to be “fully martensitic”, TEM and atom probe tomography have revealed nanoscale iron carbide precipitates that have transformed within martensitic lathes. These nanoscale precipitates have been identified to be the carbon ordering Fe4C phase. These steels were then hydrogen charged by electrolysis revealing that these carbides act as traps. This paper will address the experimental details of hydrogen charging and postulated geometric rationales why the Fe4C can trap the hydrogen within its interior rather than other carbides, which report trapping at the interface of carbide and steel matrix.
