Influence Of New Heat Treatment Process On The Microstructure And Properties Of Deforming Aluminum Alloy

2024aluminum alloy, belonging to Al-Cu-Mg deforming aluminum alloy,can be strengthened by heat treatment. This kind of alloy is widely used inindustrial production with its low density, high strength, and goodabrasion-resistance. The performance of deforming aluminum alloy has aclose relationship with heat treatment process. At present, heat treatmentprocesses for2024aluminum alloy are concentrated in solid solutionprocessing+natural aging. In order to meet the different needs of performancein each industry, it is necessary to study the different heat treatment system forperformance requirements. The influence of thermomechanical treatment,double-aging and RRA on the properties of2024aluminum alloy is studiedthrough room temperature uniaxial tensile, metalloscope, scanning electronbreak scanning, XRD phase analysis, cupping test and bending experiment,The main research results are as follows:(1)2024aluminum alloy plate in thermomechanical treatment, the colddeformation before aging can improve aging hardening characteristics andaccelerate the process of aging, shorten the aging time, and thus the strengthof the alloy was dramatically improved. Adequate amount of the deformationcan improve dislocation density, refining precipitated phase, so as to improvethe strength of the material. In this experiment, the40%of the deformation ofthe alloy strength reaches the highest.(2) For double-aging of2024aluminum sheet, as the duration of endingaging increases, the strength of the alloy first increases and then decreases;while the elongation increases. Short ending aging time will lead to small sizeand amount of sub-stable precipitated phase, which can’t strongly preventdislocation motion, so the effect of aging strengthening is not obvious, andalloy displays low strength and high plasticity. When precipitated phase issuitable in size and amount, the strengthening effect will be best. As the timeof aging increases, some sub-stable phase which size is little then the criticalwill dissolve in matrix again, and the strength decreases. (3) As the time of artificial ending aging increases, serrated yieldingbegins later, and stress drop becomes lager. The interaction between mobiledislocations and precipitated phases is the main factor to serrated flow.(4) In the regression and aging experiments, the results shows that, withthe regression temperature rises, alloy strength first increases, then decreases,and in270℃gets to peak, then down gradually. In the early stages of theregression, higher temperature leads to a large number of GP zone and smallprecipitated phase dissolve in matrix, so the strength is low. As thetemperature rises, insoluble GP zone promotes the original precipitated phasegrowing up and new precipitated phase forming. Larger size of matrixprecipitated phase blocks dislocation cutting and promotes sliding. Alloystrength gradually rises, continues to increase aging time, making precipitatedphase thicker in grains and grain boundaries, and the strength of alloy beginsto decline.