Deformation Mapping and the Role of Carbides on the Microstructure and Properties of Evolved Adiabatic Shear Bands
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INHOMOGENEOUS plastic deformation at high strain rates and large strain results in strain localization within narrow bands known as adiabatic shear bands (ASBs).[1–10] Several mechanical and microstructural factors have been reported to influence the susceptibility of structural materials to the formation of ASBs.[1–9] The effect of carbides and second-phase particles in metallic materials on the formation of ABSs has been studied by various investigators.[1,11–14] It was shown that the presence of carbides/second-phase particles in the priordeformation microstructures increases their susceptibility to the formation of ASBs during high strain rate deformation.[9,12] However, the latent effect of the SOLOMON BOAKYE-YIADOM, Research Associate, is with the Department of Mechanical and Manufacturing Engineering, University of Manitoba, E3-177 EITC, Winnipeg, MB R3T 5V6, Canada. Contact e-mail: [email protected] ABDUL KHALIQ KHAN, Research Associate, is with the Department of Mechanical and Manufacturing Engineering, Manitoba Institute of Materials (MIM), E1-277 EITC, Winnipeg, MB, Canada. NABIL BASSIM, Professor, is with the Department of Mechanical and Manufacturing Engineering, University of Manitoba, E1-382 EITC, Winnipeg, MB, R3T 5V6, Canada. Manuscript submitted March 28, 2014. Article published online August 14, 2014 METALLURGICAL AND MATERIALS TRANSACTIONS A
carbides/second-phase particles on the structure and properties of evolved ASBs are still under investigation. Crack nucleation and propagation within ASBs leading to fracture and fragmentation have been attributed to the brittle nature of the structure within the shear bands with their associated high residual stresses.[1–9] Thermomechanical and/or microstructural mechanisms which have been used to explain the evolution of ASBs is unable to adequately explain the properties and the structure within the evolved shear bands. Rittel reported that the physical picture on the phenomenon of ASBs is inadequate because there is no connection between the reported mechanical quantities and microstructural observations.[15,16] The prevailing theory for the formation of ASBs is that they form in narrow bands because of two competing mechanisms occurring sequentially: strain hardening followed by thermal softening from the retained heat due to the impact.[2,3,8,12,17] However, other investigators have used infrared techniques and computer simulations to suggest that the observed temperatures are inadequate to affect the mechanical properties of the material and are unable to account for the structure within the evolved ASBs.[1,7,9,15,16,18–20] These investigators argued that thermal softening can affect the mechanical properties of the material leading to strain localization only when the rise in temperature is at VOLUME 45A, NOVEMBER 2014—5379
least equal to the homologous temperature of the material during deformation.[1,15,18–20] In addition, dynamic recovery (DR) and dynamic recrystallization (DRX) have been used to explain the evolution of ASBs because of t
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