| This paper took 7A04 aluminum alloy materials as the research object. The sample is divided into two parts and heat treatment,two samples were carried out on the hot extrusion test,one for the T6 state of the sample, and the second for T5 state of the sample.,and compare the test results, obtained the best technical parameters.Results of themet allurgieal analysis show that the high temperature and the violent deformation during the hot extrusion brings large distortion energy and high dislocation density to the7A04 aluminum alloy,facilitates the gather of the particles of second phase and intensifies the thermal-effect of extruding,thus leads to dynamic re-crystallization.During the hot compression of 7A04 Al alloy, when the temperature rises and Intense deformation make the 7A04 aluminum alloy to be stored in a large number of distortion. Dislocation density make aggravated second-phase particles segregation and deformation heat effect, resulting in the alloy to promote the occurrence of dynamic recrystallization.After 7A04 cast aluminum alloy by 470±5℃T6 treatment, its strength and hardness are higher than the lower temperature and the lower violent deformation, and the elongation increased 70%, the section shrinkage increased 2 times, its extensibility was heightened greatly, the forming property got great improvement ultimately. According to the measured experimental data analysis:Influence of extrusion process parameters on mechanical properties of 7A04 aluminum alloy mainly by controlling the organization shape an dsize of Grain,and distribution of second phase. During hot compression deformation subgrain structure formed, When the deformation is less than 30%, Alloy dynamic recovery only occurs, When the deformation is more than 60%, Alloy started to occur in dynamic re-crystallization. Dynamic re-crystallization grain size increases with the deformation decreases. As the deformation temperature elevated, alloy dynamic re-crystallization occurred and thus a fine grain size.T6 aluminum alloy for example:In the different extrusion ratios, with the extrusion temperature rising of 7A04 aluminum alloy, subgrain rotation and aggregate easily, develop as the core of dynamic recrystallization, so that when the thermal deformation of the nucleation rate increases,with strength of larger but also increased plasticity and toughness. At various deformation temperatures, as the deformation increases, second-phase of 7A04 particles along the grain boundary precipitation, leading to a second phase of aggregation and coarsening and making it easy to place around the dislocation pileup, which will be conducive to dynamic re-crystallization nucleation.Deformation temperature of 480℃and 75% of deformation is the high strength alloy can get the optimum technology,σb=582MPa,δ=9% andΨ=14.2%.T5 aluminum alloy for example:In the different deformation temperatures, when 7A04 aluminum alloy increased as the deformation, subgrain combined dynamic recovery occurs, the intensity reduce in the first, Deformation resulting from increased promotion of dynamic recrystallization,which make Intensity and Plasticity increased significantly. In the different extrusion ratios, With deformation temperature the strength and plasticity of 7A04 increase. Deformation temperature of 480℃, the strength of materials is to improve the best temperature,σb=328MPa;Temperature is higher than 400℃, Alloy plastic is better. The maximum value isδ=19%,Ψ=32.6%.In a word, this experiment comprehensive analysis about influence of extrusion process parameters on mechanical properties of 7A04 aluminum alloy, the results show that the alloy after T6 and T5 treatment and hot extrusion deformation process at the above-mentioned conditions can effectively improve the mechanical properties of alloys at room temperature,which supply a scientific basis for the improvement of the extrusion parameters and the improvement of product property on the microstructure and mechanical properties. |
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