The use of tailor-welded blanks (TWBs) in the automotive industry helps to meet an ever-increasing demand for lightweight, safe, and crash-resistant structural components for modern vehicles. These blanks enable the production of intricately optimized load-bearing assemblies that are both lightweight and exceptionally robust. One such application is evident in the fabrication of B-pillars, where laser-welding different press-hardened steels (PHSs) creates components that have tailored elongation properties for enhanced energy absorption and increased yield strength for improved structural integrity under high dynamic loads. However, the laser welding of aluminum-silicon (Al-Si) coated PHSs results in the formation of a softer ferrite phase in the welded joint which is attributed to the mixing of the Al-Si coating in the molten weld pool, resulting in a catastrophic premature failure of the joint. Current industry practice involves pre-weld removal of the Al-Si layer through laser ablation, but this can be costly and time-consuming. This presentation discusses the use of in-situ alloying of Ni during laser welding that solves the issue of softening without the prior removal of the Al-Si coating. Research findings have shown that the introduction of Ni into the joint as an austenite stabilizing element can decrease ferrite content and increase weld strength without sacrificing process efficiencies. This presentation will explore in detail the impact of in-situ alloying of Ni with 22MnB5 to analyze how the morphology, crystallography, and mechanical properties of the resulting fusion zone can be improved. This investigation offers insights into potential advancements in developing new press-hardened steels and other advanced materials processing techniques that have applications in several important industries.
Keywords: Fiber laser welding; press-hardened steels; ferrite suppression; tailor-welded blanks; surface modification; austenite stabilizing elements; hot stamped steel; Al-Si coated 22MnB5
Dr. Muhammad Shehryar Khan is a Banting Postdoctoral Fellow in the field of advanced materials processing within the Department of Materials Science and Engineering at MIT. He also serves as an adjunct professor in the Department of Mechanical and Mechatronics Engineering at the University of Waterloo, from where he received his Ph.D. in Mechanical and Mechatronics Engineering. In 2023, Dr. Khan was awarded the Governor General’s Gold Medal for his graduate work which is one of the highest academic honors given in Canada. He is a recipient of the Natural Sciences and Engineering Research Council (NSERC) Postgraduate Scholarship (2020-2022) and the Alexander Graham Bell Canada Graduate Scholarship (2022-2023), and most recently, he was ranked 1st out of 159 world-class doctoral applicants in the internationally-contested Banting Postdoctoral Fellowship competition in 2023.
Dr. Khan works in the realm of advanced materials processing with his core research interests lying at the intersectional understanding of relationships between process, microstructure, and properties of materials, with a focus on advancing the fields of mechanical engineering, materials science, and advanced manufacturing. He has a keen interest in addressing real-world processing and advanced materials related challenges faced by various industries including automotive, aerospace, and the energy sectors. He has published research in materials processing topics related to high-speed high-power laser processing of steels and other materials including laser welding and laser cladding. He has also published fundamental studies related to a non-fusion joining process called weld-brazing that uses Cu-based filler materials to join high strength steels used in the automotive industry. He also specializes in dissimilar joining of structural materials and various issues related to industrial metallurgy ranging from liquid metal embrittlement of Zn-coated steels to microstructural refinement of steels using in-situ alloying and processing techniques. He is currently utilizing laser-induced particle impact testing (LIPIT) to study fundamental issues related to cold spraying technology, which is a solid-state powder deposition process that achieves impact-induced mechanical or metallurgical bonding at extremely high strain rates. His ongoing research explores bonding mechanisms for various materials, including pure metals and alloys, to shed light on solid-state bonding behaviors in industrially relevant dissimilar materials.
Banting Postdoctoral Fellow, Department of Materials Science and Engineering, Massachusetts Institute of Technology