Professor Kester Clarke

Colorado School of Mines

Thermomechanical processing for metal manufacturability and performance

Metallic alloy processing and service conditions have significant effects on our ability to efficiently manufacture metals with desired microstructures and implement those metals in performance critical applications. Third-generation advanced high strength steels containing metastable retained austenite have resulted in cost-efficient structural steels with unprecedented performance for automotive structural applications. That performance is most commonly quantified in the laboratory by tensile testing at quasi-static strain rates. Both manufacturing processes such as stamping and in-service deformation due to crash events deviate significantly from the strain state, path, rate, and temperature conditions commonly tested. Thus, tailoring austenite stability is critical for optimizing the forming response and crash performance of quenched and partitioned grades. Accumulative roll bonding (ARB) affords the ability to create fine-grained microstructures with otherwise unobtainable properties, but bulk manufacturability is limited by severe edge cracking that occurs due to the necessary large, single-pass rolling reductions. Here we show that lateral constraint can significantly reduce or eliminate edge cracking and maintains improved thickness homogeneity during ARB of aluminum alloys. This methodology greatly improves sample quality and yield when applied to multiple ARB cycles and is scalable to bulk manufacturing processes, allowing for microstructure design toward lower temperature superplastic forming and improved strength in service.

Bio:

Dr. Kester Clarke is an associate professor in the Metallurgical and Materials Engineering Department at Colorado School of Mines and serves as the Forging Industry Education and Research Foundation (FIERF) Professor. He holds a joint appointment as a scientist at Pacific Northwest National Laboratory (PNNL) and is a visiting scientist at Los Alamos National Laboratory (LANL). He engages in research on deformation processes in metal alloys and serves as the Industry Liaison Officer for the Center for Advanced Non-Ferrous Structural Alloys and collaborates with the Advanced Steel Processing and Products Research Center. His research interests include alloy development, material deformation and fabrication processes, and the use of experimental and modeling methods to examine the effect of material processing history and microstructure on mechanical properties and performance. Dr. Clarke holds a B.A. in Psychology from Indiana University, a B.S. in Materials Science and Engineering from Wayne State University, and M.S. and Ph.D. degrees in Metallurgical and Materials Engineering from the Colorado School of Mines. He has worked as a consulting Metallurgical Engineer for Engel Metallurgical and as a Senior Engineer/Research and Development for Caterpillar.  He conducted postdoctoral research at Los Alamos National Laboratory, was an R&D scientist/engineer serving as the technical lead for thermal-mechanical processing of metals and metal component fabrication.  

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