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The effects of thermomechanical treatment (TMT) on the engineering properties of aluminum alloys are discussed. At present, only one type of TMT seems commercially practicable. This is a T3XX type treatment for 2000 series alloy sheet. Of the other kinds of TMT those with the most potential are high-temperature aging final thermomechanical treatments (FTMT). Factors unfavorable to commercial exploitation of TMT are the extra costs, particularly if hot working is involved, the significant improvements in properties obtainable from conventionally processed newer alloys, the promising results for powder metallurgy alloys, which, however, also entail additional processing costs, and the lack of consistent improvement of fatigue properties by TMT. The main incentive for continued investigation of TMT and the most likely key to its commercial exploitation is the possibility of improving fatigue properties.
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Effect of large cold deformation on the age-hardening characteristics of 2024 aluminum alloys was investigated. The results reveal: 1) the aging response is accelerated after large cold deformation, and the peak strength is attained after aging for 40 min; 2) double aging peaks can be found in the age-hardening curves, and the first peak appears when aged for 40 min. The corresponding peak tensile strength (σb) and elongation are up to 580 MPa and 9.2% respectively, the second peak appears when aged for 120 min, but the peak tensile strength (520 MPa) is lower than the first one; 3) in early stage of aging (
The effect of grain size upon the stress corrosion cracking of 7475 Al-alloy plates has been investigated. Grain refinement resulted in a more homogeneous slip mode and a smaller size of grain boundary precipitates (GBPs) to influence the stress corrosion cracking (SCC) resistance. The more homogeneous slip mode is always beneficial for improving the SCC resistance. However, if the GBPs size was smaller than a critical precipitate size for nucleating hydrogen bubbles, the improvement of SCC resistance due to grain refinement, resulting from a more homogeneous slip mode, could not be obtained. The correlation of SCC susceptibility and hydrogen embrittlement susceptibility has been evaluated. The SCC susceptibility of the 7475 aluminum alloys is mainly controlled by hydrogen induced cracking mechanism.
Mechanical properties of age-hardenable aluminum alloys can be markedly improved by proper application of thermomechanical treatment (TMT). The degree of improvement in mechanical properties was indicated to be dependent upon TMT cycles and the alloy composition. The objective of the present work was to study the changes in microstructure and tensile properties of an AlMgSi alloy at room and elevated temperatures, produced by applying cold rolling reductions before aging at various temperatures.
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