Abstract
Tensile tests were conducted on the aluminum alloy, AA6111, after various artificial aging treatments in order to examine the influence of precipitation state on yield stress and work-hardening behavior. During artificial aging, significant changes in the work-hardening rate were observed as the precipitation reaction proceeded. A semiempirical model has been developed to interpret these changes in work-hardening rate. This model shows that the significant changes in work-hardening rate can be related to the manner in which flow stress contributions from different obstacles are summed and the transition from shearable to nonshearable precipitates. The present study presents a new approach to determining the shearable/nonshearable transition from a series of tensile tests. Results on the aluminum alloy AA7030 were also found to be consistent with the proposed theoretical framework. Finally, the proposed model allows the overall mechanical response for a variety of aging conditions to be rationalized.
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Abbreviations
- α D :
-
constant relating to the storage of geometrically necessary dislocations
- α ⊥ :
-
constant in the relationship between dislocation density and flow stress
- b :
-
magnitude of the Burgers vector
- k 1 :
-
dislocation storage rate term due to statistically stored dislocations
- k 2 :
-
dislocation storage rate term due to dynamic recovery
- k D :
-
dislocation storage rate term due to geometrically necessary dislocations
- f, f s , f ns :
-
constants representing the modification of the dynamic recovery due to precipitate effects; subscripts s and ns refer to shearable and nonshearable precipitates
- F :
-
strength of nonshearable precipitates
- G :
-
shear modulus
- L :
-
spacing of precipitates on the glide plane
- M :
-
Taylor factor
- n :
-
exponent used in flow stress addition law
- ε :
-
total strain
- ε P :
-
plastic strain
- ρ :
-
dislocation density
- σ :
-
overall total flow stress of the alloy
- σ ss :
-
solid solution contribution to flow stress
- σ ppt :
-
precipitation-hardening contribution to flow stress
- σ Y :
-
yield stress
- σ ⊥ :
-
dislocation hardening contribution to flow stress
- σ ⊥s :
-
saturation stress for dislocation hardening contribution
- T :
-
line tension of the dislocation=G b 2/2
- θ ⊥ :
-
work-hardening rate for dislocation hardening
- θ ⊥o :
-
initial work-hardening rate for dislocation contribution to flow stress
- θ :
-
overall work-hardening rate of alloy
- θ max :
-
overall initial work-hardening rate of alloy as defined in Fig. 3
- dθ/dσ :
-
as defined in Fig. 3
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Cheng, L.M., Poole, W.J., Embury, J.D. et al. The influence of precipitation on the work-hardening behavior of the aluminum alloys AA6111 and AA7030. Metall Mater Trans A 34, 2473–2481 (2003). https://doi.org/10.1007/s11661-003-0007-2
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DOI: https://doi.org/10.1007/s11661-003-0007-2