Abstract
Strips of 99.95 at.% Mo polycrystals annealed at 700 °C as well as the ones annealed and then aged for 6 months at room temperature were deformed in tension at various strain-rates in the range 2.1 × 10−4 to 4.2 × 10−3 s−1 till fracture. It is found that natural aging of the annealed specimens for 6 months leads to 20-30% reduction in the yield stress (YS), 18-22% reduction in the ultimate tensile strength (UTS), and 72-76% reduction in the ductility, i.e. the tensile strain εmax corresponding to UTS, depending on the value of \( \dot{\upvarepsilon } \) in the tensile strain-rate range referred to. Data analysis in terms of the kink-pair nucleation model of flow stress shows that the reduction in YS of the aged Mo specimens is a consequence of lowering of the Peierls energy per interatomic spacing along the length of screw-dislocation segments trapped in the Peierls valleys on the migration of point defects to the dislocation cores during the course of natural aging. The reduction in UTS and εmax is attributed to the variation in the relative contribution of the processes of dislocation multiplication and annihilation together with the reduction in the Peierls stress of the metal.
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References
R. Golovchak, A. Kozdras, O. Shpotyuk, S. Kozyuklin, and J.-.M. Saiter, Long-Term Aging Behaviour in Ge-Se Glasses, J. Mater. Sci., 2009, 44, p 3962–3967
S.V. Nemilov, Physical Aging of Silicate Glasses at Room Temperature: The Choice of Quantitative Characteristics of the Process and the Ranking of Glasses by Their Tendency to Aging, Glass Phys. Chem., 2001, 27, p 214–227
P. Boolchand, D.G. Georgiev, and B. Goodman, Discovery of the Intermediate Phase in Chalcogenide Glasses, J. Optoelectron. Adv. Mater., 2001, 3, p 703–720
A. Asif and M.Z. Butt, Analysis of Observations on Solid-Solution Hardening in KBr-KCl Single Crystals, J. Mater. Sci., 2007, 42, p 2862–2866
A. Asif and M.Z. Butt, Analysis of Temperature and Concentration Dependences of Flow Stress in KCl-KBr Single Crystals with Special Reference to the Nature of Solute Distribution, Phil. Mag., 2007, 87, p 1811–1820
V.V. Demirskiy, S.N. Komnik, and V.I. Startsev, Work Hardening of Single Crystals of Copper-Aluminum α Solid Solutions in the Range 4.2-300 K, Phys. Met. Metall., 1979, 46, p 51–158
R. Ruf and D. Koss, Solid-Solution Hardening of the Ternary System Nb-Hf-W, Phil. Mag., 1974, 30, p 1319–1326
C. Schwink and T. Wille, On the Concentration Dependence of Stress Equivalence in Solid Solution Hardening, Scripta Metall., 1980, 14, p 1093–1100
A. Varschavsky and E. Donoso, A Calorimetric Investigation on the Kinetics of Solute Segregation to Partial Dislocations in Cu-3.34 at.%Sn, Mater. Sci. Eng. A, 1998, 251, p 208–215
R.C. Picu, G. Vinczc, J.J. Gracio, and F. Barlat, Effect of Solute Distribution on the Strain Rate Sensitivity of Solid Solutions, Scripta Mater., 2006, 54, p 71–75
H. Sieurin, J. Zander, and R. Sandstrom, Modelling Solid Solution Hardening in Stainless Steels, Mater Sci. Eng. A, 2006, 415, p 66–71
M.Z. Butt and F. Aziz, Effect of Heterogeneous Solute Distribution on the Anomalous Theremo-Mechnical Response of Cu-Ni Alloy Single Crystals Below 50 K, Phil. Mag. Lett., 2007, 87, p 915–922
M.Z. Butt, M. Noshi, and F. Bashir, Onset of Local Ordering in Some Copper-Based Alloys: Critical Solute Concentration Vis-à-Vis Various Solution Hardening Parameters, Cent. Europ. J. Phys., 2008, 6, p 834–842
M.Z. Butt, M. Zubair, and I. Ul-Haq, A Comparative Study of the Stress Relaxation in Aged and Un-Aged High-Purity Aluminium Polycrystals, J. Mater. Sci., 2000, 35, p 6139–6144
M.Z. Butt, A.Q. Jakhar, and H. Aslam, Effect of Natural Aging on the Strain-Rate Sensitivity of Flow Stress in High-Purity Aluminium Polycrystals, Phys. Stat. Sol. (a), 1999, 176, p 877–884
M.Z. Butt and F.A. Khwaja, Effect of Aging on the Strength of High-Purity Aluminium, J. Nat. Sci. Math., 1995, 35, p 1–4
M.Z. Butt and P. Feltham, Work Hardening of Polycrystalline Copper and Alpha-Brasses, Metal Sci., 1984, 13, p 123–126
F. Bashir and M.Z. Butt, Effect of Natural Aging on the Mechanical Properties of Molybdenum Polycrystals, J. Mater. Sci., 2007, 42, p 7801–7805
M.Z. Butt, M. Khaleeq-ur-Rahman, and D. Ali, On the Strain-Rate Dependence of Flow Stress in Crystals with High Intrinsic Lattice Friction, J. Phy. D: Appl. Phys., 2009, 42, p 035405
M.Z. Butt, Kinetics of Flow Stress in Crystals with High Intrinsic Lattice Friction, Phil. Mag., 2007, 87, p 3595–3614
T.E. Mitchell, P. Peralta, and J.P. Hirth, Deformation by a Kink Mechanism in High Temperature Materials, Acta Mater., 1999, 47, p 3687–3694
R.L. Fleischer, Substitutional Solution Hardening, Acta Metall., 1963, 11, p 203–209
F.R.N. Nabarro, Solution Hardening, Dislocations and Properties of Real Materials, M.H. Loretto, Ed., The Institute of Metals, London, 1985, p 152–169
R.E. Reed-Hill and M.J. Kaufman, On Evaluating the Flow Stress in Niobium of Commercial Purity, Acta Metall. Mater., 1995, 43, p 1731–1739
G.A. Malygin, Structure Factors that Influence the Stability of Plastic Strain of bcc Metals Under Tensile Load, Phys. Solid State, 2005, 47, p 896–902
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Special thanks are due to the Pakistan Council for Science and Technology, Government of Pakistan, Islamabad, for financial assistance under the Research Productivity Allowance Scheme. We are also indebted to the reviewers for their constructive criticism and valuable suggestions.
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Bashir, F., Butt, M.Z. & Ali, D. On the Change in Work Hardening Characteristics of Molybdenum Polycrystals Due to Natural Aging. J. of Materi Eng and Perform 20, 250–256 (2011). https://doi.org/10.1007/s11665-010-9665-6
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DOI: https://doi.org/10.1007/s11665-010-9665-6