Mechanical and microstructural characterization of magnesium single crystals
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Svitlana Fialkova and Sergei Yarmolenko Center for Advanced Materials and Smart Structures, North Carolina A&T State University, Fort Interdisciplinary Research Center, Greensboro, North Carolina 27411, USA
Vesselin Shanova) Department of Mechanical and Materials Engineering, University of Cincinnati, Cincinnati, Ohio 45221, USA; and Department of Biomedical, Chemical and Environmental Engineering, University of Cincinnati, 601 Engineering Research Center, Cincinnati, Ohio 45221, USA (Received 1 June 2017; accepted 4 October 2017)
This study describes results from mechanical tests conducted on magnesium single crystals in comparison with polycrystalline magnesium. It was found by impact testing that the magnesium single crystal is highly ductile due to energy absorption by twinning and slip, while the polycrystalline samples fracture easily upon impact. Compressive testing along two orthogonal directions at low plastic strains was also performed. The microstructure studies by electron backscatter diffraction and XRD pole figure analysis revealed profuse (1012) twinning when compression is done along the growth plane (72 16 88 62). The twinning and interaction between different twin modes resulted in incipient recrystallization at strains as low as 8% at room temperature. Compression along the nearly orthogonal plane (2 2 4 15) was marked by a much lower degree of both twinning and recrystallization. The variation in microstructural response with the orientation of loading allows for a wide range for tailoring mechanical properties of pure magnesium single crystals without any need of alloying.
I. INTRODUCTION
Magnesium has generated a lot interest in the field of biomedical implants recently, owing to its biodegradable nature.1,2 Its density and mechanical properties are close to that of the human bone tissue, making it particularly attractive for orthopedic and craniofacial implants.1,3 There has also been interest toward the application of magnesium and its alloys in cardiovascular stents, meshes, as well as other sutures.4 Additionally, Mg and its alloys have several applications in the automotive industry.5 In most of these applications, the mechanical properties and behavior are key for optimum performance. The deformation mechanisms on magnesium single crystals were first investigated several decades ago using compression as the primary mode of deformation in these studies.6–9 This was used to observe the slip and twinning mechanisms when stress was applied along different crystallographic directions involved in the deformation of Mg. With the development of modern characterization techniques, such as severe plastic and
Contributing Editor: Jürgen Eckert a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2017.419
high-strain-rate deformation, nano indentation, electron backscatter diffraction (EBSD), high resolution transmission electron microscopy, and crystal plasticity modeling have been used to obtain more accurate information on the deformation microstructur
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