Extrusion Process Of4045/3003Aluminum Alloy Bimetal Tubes

As the key material of efficient all-aluminum heat exchanger,4045/3003aluminum alloy bimetal composite tube is widely used in automotive andair-conditioning sectors. In this paper, hot compression tests of4045aluminum alloywere preformed on Gleeble-3500, and the mechanical behavior and microstuctureevolution under high-temperature compression are analysed. Finite element numericalsimulation software combined with experiment are used to analyse the influence of dieangle, extrusion temperature, extrusion speed, the initial billet thickness ratio andother parameters on the distribution of the cladding layer during extrusion process.The results are shown as following:The flow stress of4045aluminum alloy during hot compression deformationdecreases as the temperature increases, and increases as the the strain rate increases,which can be represented by the Zener-Hollomon parameter Z in the hyperbolic sineequation with the hot deformation activation energy of189.9kJ/mol.According to the dynamic model and microstructure analysis of the experimental,the instability area of4045aluminum is mainly concentrated in areas of high strainrate. As the strain increases, the instability region enlarges. At deformationtemperature of380-450oC and strain rate of0.1-0.3s-1, the alloy can be well processed.With the Z value decreases, dynamic recovery show a enhancement during hotdeformation. Sub-grain boundary gradually become clear and straight, dynamicrecrystallization gradually work. Two kinds of phase was observed through SEM, themainly difference of the two phases are the content of silicon. Two kinds of particlediffer in size are observed through TEM, each of them undergo a refinement orspherical as Z value decreased.Unstable longitudinal distribution of cladding layer thickness along the productlength occurred during the clad extrusion of4045/3003aluminum alloy bimetal tube.By analyzing the effect of die angle, extrusion temperature, extrusion speed andcoated billet thickness on distribution of composite pipe thickness ratio, thereasonable process parameters (die angle45o, textrusion temperature of420oC andextrusion speed of5mm/s) was obtained, under which the coating layer thicknessdistribution is most stable. The relationship between coated billet thickness ratio andthe cladding layer thickness ratio was also verified in this condition. Linear fitting wasused to obtain the linear equation of the percentage of cladding billet of the total billet and the percentage of coating layer thickness of the total thickness of the dual metalpipe: y1.06x1.83.The actual extrusion results are consistent with the result of numerical simulation,which were verified by the experiment. It indicated that the numerical simulationshave high accuracy and reasonableness.