Experimental Investigation of Dynamic Abnormal Grain Growth

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TECHNICAL SUMMARY: Dynamic abnormal grain growth (DAGG) is a recently-discovered secondary recrystallization phenomenon that occurs only during plastic deformation at elevated temperature. DAGG can rapidly produce very large single crystals in the solid state at relatively low homologous temperatures, approximately 0.65 Tm, a feat not possible by any other process. The dynamic nature of DAGG is its most unique characteristic and poses new challenges to current understandings of abnormal grain growth and grain-boundary migration, foundational topics in the metals science of microstructure evolution. To date, DAGG has been observed in only two materials, Mo and Ta BCC refractory metals. The proposed research will investigate the processes which give rise to DAGG in these metals and then develop new metal systems susceptible to DAGG. Research goals include developing (1) a capability to predict when and in what materials DAGG will occur and (2) a capability to control DAGG in materials susceptible to abnormal grain growth. The resulting mechanistic understanding of DAGG will be used to predict the occurrence of DAGG under conditions of technological importance.NON-TECHNICAL SUMMARY: Dynamic abnormal grain growth (DAGG) is a recently-discovered phenomenon in the field of materials science. DAGG occurs while deforming polycrystalline material at elevated temperature and has been used to grow large single crystals in molybdenum and tantalum for scientific studies. Beyond this initial practical application, DAGG represents an opportunity to gain new fundamental insights into the evolution of material microstructure. Controlling material microstructure is critical to the manufacture of advanced components in many industries, particularly the transportation industries. Potential impacts of this research include creating new materials and improving the quality of manufactured components. The proposed research will enhance collaborations with General Motors and Sandia National Laboratory. Both graduate and undergraduate students will be trained in the fields of materials and metals science through research activities and as well as mentoring during academic studies. Outreach activities which promote science and engineering to the local community will be supported.