Microstructural Origin of Residual Stress Relief in Aluminum
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INTRODUCTION
DEFORMED aluminum typically shows[1–3] a hierarchy of dislocation substructures. The latter may range from deformation bands and strain localizations to cell blocks and dislocation cells. Any such substructure is also expected[4–6] to be associated with the evolution of residual stresses. Post-deformation annealing often modifies the substructure,[1,2,7–9] and thus enables residual stress relief.[10,11] This is the so-called thermal stress relief: a subject of both applied and academic interest. However, correlating substructure evolution with residual stress relief is a tedious experimental task that has
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. Contact e-mail: [email protected] ADITYA PRAKASH and INDRADEV SAMAJDAR are with the Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Mumbai, 400076, India. SHYAM M. KERALAVARMA is with the Department of Aerospace Engineering, Indian Institute of Technology Madras, Chennai, 600036, India. A. AMINE BENZERGA is with the Department of Aerospace Engineering, Texas A&M University, College Station, TX 77843 and also with the Department of Materials Science and Engineering, Texas A&M University, College Station, TX 77843. CHRISTOPHER HUTCHINSON is with the Department of Materials Science and Engineering, Monash University, Clayton, VIC 3800, Australia. Manuscript submitted December 12, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS A
rarely been attempted. Furthermore, the physics underlying any such correlations cannot be fully revealed on the sole basis of experiments. One of the reason for this is the relatively small time-scale involved. It is to be noted that the time-scale associated with pre-recrystallization recovery may range from a fraction of a second to a few seconds at best. The present study thus sets out to address possible correlations by combining experimental measurements with discrete dislocation dynamics (DDD) simulations. The DDD simulations are expected to account for key processes believed to drive microstructure evolution during annealing. The residual stress can be viewed both mechanistically and from an atomistic perspective,[2,12] the latter being more appropriate to the present study. This happens as the stress-free equilibrium lattice spacing (d0) is changed to a non-equilibrium value. The constraints allow retention (fully or in part) of such non-equilibrium value after the external stresses are removed. Naturally, the constraints are important to the subsequent stress relief. In a deformed material, the dislocation substructures may provide such constraints.[2] Annealing, on the other hand, modifies the dislocation substructures and thus enables a stress relief. In general, annealing involves both recovery and partial recrystallization. Recovery is driven by
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