Structural influences on the work hardening behavior of aluminum

Thesis/Dissertation · Thu Dec 01 00:00:00 EST 1994

DOI:https://doi.org/10.2172/64278· OSTI ID:64278

Chu, David ^[1]

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1. Univ. of California, Berkeley, CA (United States)

Effects of various grain and subgrain morphologies on low temperature work hardening of pure Al is studied using tensile tests. Plotting the work hardening rate as a function of true stress, the work hardening is separable into two distinct regimes. Both regimes are approximated by a line θ = θ₀ - K₂σ, where θ₀ is theoretical work hardening rate at zero stress and K₂ is related to dynamic recovery rate. The first or early deformation regime exhibits greater values of θ₀ and K₂ and can extend up to the first 10% strain of tensile deformation. This early deformation regime is contingent on the existence of a pre-existent dislocation substructure from previous straining. The θ₀ and K₂ associated with the early deformation regime are dependent on the strength and orientation of the pre-existent dislocation substructure relative to the new strain path. At high enough temperatures, this pre-existent dislocation substructure is annealed out, resulting in the near elimination of the early deformation regime. In comparison, the latter regime is dominated by the initial grain and/or subgrain morphology and exhibit lower values of θ₀ and K₂. The actual value of K₂ in the latter regime is strongly dependent on the existence of a subgrain morphology. Recrystallized or well-annealed microstructures exhibit greater values of K₂ than microstructures that remain partially or fully unrecrystallized. The higher K₂ value is indicative of a more rapid dynamic recovery rate and a greater degree of strain relaxation. The ability to achieve a more relaxed state produces a low-energy cellular dislocation substructure upon deformation. The introduction of subgrains hinders the evolution of a low-energy dislocation cell network, giving way to a more random distribution of the dislocation density.

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 64278
• Report Number(s): LBL-36547; ON: DE95011262
• Resource Relation: Other Information: TH: Thesis (Ph.D.); PBD: Dec 1994
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM
STRAIN HARDENING