Relating Residual Stress and Substructural Evolution During Tensile Deformation of an Aluminum-Manganese Alloy
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INTRODUCTION
ASPECTS of polycrystalline plasticity offer an interesting challenge to the materials community. Typically in a metallic material, deformation-induced crystallite imperfections, mainly dislocations, interact and a longrange dislocation patterning or substructure evolution occurs.[1–5] As a consequence of this evolution, orientation gradients evolve inside individual grains, breaking it into small blocks.[6] This results in subgrain boundaries which contain excess dislocations that are necessary for accommodating the imposed curvatures (known as geometrically necessary dislocations or GNDs).[7–9] As deformation progresses, the number of mobile dislocations increase as well as new dislocation sources are activated. Simultaneously, the grains do not undergo the same amount of deformation because the flow stress of an individual grain is a function of its crystallographic orientation.[10] When an external load is applied to a polycrystalline material, each grain experiences
ARIJIT LODH is with the IITB-Monash Research Academy, Indian Institute of Technology Bombay, Mumbai, 400076, India. TAWQEER NASIR TAK and P.J. GURUPRASAD are with the Department of Aerospace Engineering, Indian Institute of Technology Bombay, Mumbai, 400076, India. ADITYA PRAKASH and INDRADEV SAMAJDAR are with the Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology 7 Bombay, Mumbai, 400076, India. Contact e-mails: [email protected], [email protected] CHRISTOPHER HUTCHINSON is with the Department of Materials Science and Engineering, Monash University, Clayton, 3800, VIC, Australia. Manuscript submitted April 3, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS A
constraints from its neighboring grains, and thus tries to deform in a unique manner. This creates an incompatibility in the microscopic stress state. The result of this incompatibility, at the macroscopic scale, is the residual stress development inside the deforming material. It is to be noted that the residual strain/stress values, both experimental and simulated, mentioned in this manuscript were elastic stress/strain. The objective of this study is to correlate the evolution of the substructure during monotonic deformation with the development of residual stress. In the context of this study, it is useful to distinguish between the different ‘residual stress’ nomenclatures.[11–13] The residual stress developed in a material can be divided into two categories depending on the length scale[1]: macroresidual stress and microresidual stress. Macroresidual stress (often called as type-I or bulk residual stress) spans over a large number of grains and is of interest to design engineers. Microresidual stress can be of two types: type-II (or intergranular residual stress), which varies from grain to grain due to heterogeneity and anisotropy of individual grains and are important as an indicator of strain hardening and damage to a material; and type III (or intragranular residual stress) which exists inside a grain because of crystal imperfec
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