An Extended Age-Hardening Model for Al-Mg-Si Alloys Incorporating the Room-Temperature Storage and Cold Deformation Process Stages

Abstract

In this article, a new age-hardening model for Al-Mg-Si alloys is presented (named NaMo-Version 2), which takes into account the combined effect of cold deformation and prolonged room-temperature storage on the subsequent response to artificial aging. As a starting point, the original physical framework of NaMo-Version 1 is revived and used as a basis for the extension. This is permissible, since a more in-depth analysis of the underlying particle-dislocation interactions confirms previous expectations that the simplifying assumption of spherical precipitates is not crucial for the final outcome of the calculations, provided that the yield strength model is calibrated against experimental data. At the same time, the implementation of the Kampmann-Wagner formalism means that the different microstructure models can be linked together in a manner that enforces solute partitioning and competition between the different hardening phases which form during aging (e.g., clusters, b¢¢ and b¢). In a calibrated form, NaMo-Version 2 exhibits a high degree of predictive power, as documented by comparison with experiments, using both dedicated nanostructure and yield strength data as a basis for the validation. Hence, the model is deemed to be well-suited for simulation of thermomechanical processing of Al-Mg-Si alloys involving cold-working operations like sheet forming and stretch bending in combination with heat treatment and welding.

Characterization of phase development in commercial Al-Zn-Mg(-Mn,Fe) alloy with and without Sc,Zr-addition

“…Assuming the presence of the Sc,Zr-containing particles, it can also be concluded that the yield strength of the AlZnMgScZr alloys cannot be expressed as a linear superposition of several strength contributions. This conclusion is in agreement with the observation of the others in the commercial AA6xxx alloys, see [30,31]. The AlZnMgScZr alloys show significantly higher HV values at higher temperatures in contrast to the AlZnMg alloys ( Fig.…”

Role of Small Addition of Sc and Zr in Clustering and Precipitation Phenomena Induced in AA7075

“…Assuming the presence of the primary and secondary Al3(Sc,Zr)-phase particles it can be also concluded that the yield strength cannot be captured as a linear superposition of several strength contributions. This conclusion is in an agreement with other observations in commercial 2xxx, 6xxx and 7xxx alloys, see References [20,25,65,[67][68][69].…”

Temperature Effects on the Tensile Properties of Precipitation-Hardened Al-Mg-Cu-Si Alloys

“…These models include the Kocks-Mecking model [9][10][11], the Alflow model [12], and Myhr et al's model [13]. Although these sophisticated models may include the effects of stacking fault energy, grain size, impurity element content, precipitation particle sizes/contents, etc., on the hardening behavior of alloys, we elected to use a simpler Hollomon equation (σ t = Kε t n , where σ t , ε t , K, and n are true stress, true strain, strength coefficient, and strain hardening exponent, respectively) to represent the hardening behavior of Al-A319 alloys.…”