PSI - Issue 60

B.P. Kashyap et al. / Procedia Structural Integrity 60 (2024) 494–509 B.P. Kashyap et al. / Structural Integrity Procedia 00 (2023) 000 – 000 11 Cu eutectic follows ̇ ∝ ( )̇ 0.64 type relationship (Kashyap, 1991), and the strain rate exponent is comparable with the maximum m of this material. The data of variation in grain size ( d ), cavity size ( C s ), and cavity volume ( C v ) as a function of strain were obtained at ̇ =1×10 −4 s -1 at T = 813 K (Kashyap and Tangri, 1987, 1989), and the same are plotted in Fig. 6(a) to examine some mutual relationship among them. It is noted that both C s and C v concurrently increase with grain growth following the interrelationships =1×10 −4 ( ) 4.8 R 2 = 1 (20) =1×10 −23 ( ) 22 R 2 = 1 (21) Increasing cavity volume with increasing strain occurs by increasing cavity nucleation and growth of cavities. The variation in mean cavity size C s as a function of cavity volume ( C v ) is plotted in Fig. 6(b) at 813 K, which follows the relationship =48( )+3.5 R 2 = 0.91 (22) The increasing cavity size with increasing cavity volume fraction is seen to be generally obeyed irrespective of strain rate and strain to suggest that the increasing cavity size might arise from inter-linkage of cavities at larger strain and/or higher strain rate. The variation in C v as a function of temperature is presented in the form of an Arrhenius plot to get some estimate of activation energy for cavitation in Fig. 6(c), ∝ exp( + ⁄ ) . The cavity volume by diffusional process may increase with increasing temperature but, as a consequence of plastic deformation, it may be possible that the increasing temperature, by reducing stress concentration, can help in decrease of cavity volume viz. ∝ ∝ exp( + ⁄ ) . The slope of the plot in Fig. 6(c) gives + Q / R or Q Cv = 149 kJ/mol, which are comparable with the activation energy for lattice diffusion (142 kJ/mol)(Lundy and Hurdoch, 1962), grain boundary sliding (142 kJ/mol) (Davies et al., 1965), and creep (148 kJ/mol)(Sherby and Burke, 1968) of Al.

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Fig. 6. (a) variation in cavity size and cavity volume as a function of grain size of Al-Cu system; (b) plot of cavity size vs. cavity volume at same test condition present in (a); and (c) Arrhenius plot of cavity volume variation with temperature.