Dr. Elliot Biro, Manager, Product Characterization ArcelorMittal Global Research
To improve automotive fuel economy while increasing crash resistance, automakers are increasingly using advanced high strength steels (AHSS) for their vehicle designs. AHSS is a broad term for several families of steels that have both high strength and high formability. This combination of properties allows parts to be made thinner and lighter while retaining their ability to form complex shapes needed for automotive parts as well as being able to absorb large amounts of energy in crash situations. These steels develop their properties from their multiphase microstructure. Dual-phase (DP) and martensitic steels are two families of AHSS that derive their strength from martensite in their microstructures. After welding, the martensite within these steels tempers, locally softening the material adjacent to the weld. This change in properties can affect material forming and crash performance. To be able to predict post-welding properties, isothermal softening data was fit to the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation. The JMAK curve fits were examined in detail to gain greater understanding of the metallurgical processes occurring during softening, as well, the material models were applied to thermal cycles from various laser and spot welds to predict HAZ softening.
Elliot Biro attained his bachelor’s and master’s degrees from the University of Waterloo where he specialized in welding. After graduating in 2001, he started working at ArcelorMittal Dofasco Research where he was responsible for designing and running the welding research program. During this time, Elliot concurrently completed his PhD in Materials Science and Engineering at McMaster. In 2012, he became the manager of the Product Characterization group which was responsible for metallographic and mechanical testing and development of characterization techniques. Four months ago, Elliot returned to his previous responsibilities when he became a Principal Researcher in the Research Department.