| 其他摘要 | 5B02Al is a low Mg content Al-Mg alloy which possesses excellent plasticity, anticorrosion property and weldable property. 5B02Al tubes are usually used as the parts in the aerocraft, and are the importent configurable material in the aviation fields, 5B02Al belong to non heat treatment strengthening aluminium alloy, and cold deform -ation and recrystallization have a big effect on microstructure and mechanical proper -ties of tubes. The present research has focused on the attention to the microstructure and properties which are influenced by adjusting the cold process and heat treatment. Primary researching contents and results are as following；
1、The paper analyzed the cold deformation of tube drawing though calculating with upper bound solution and programming with Matlab software. Firstly，a generalized kinematically admissible velocity field suitable for axisymmetric tube drawing through die or plug is proposed.; Secondly, the internal power and the power dissipated on frictional and velocity discontinuity surfaces are calculated from the velocity field, and the total power is optimized with respect to the size changing of tube wall thickness; Lastly, the effective strain, the distribution of strain, and the deformation aberration are calculated. From calculating course of effective strain, it can can be seen that the degree of plastic deformation rest with not only the changing of intercepting aera of tube before and after deformation, but also with the conical converging angle. Effects of various process parameters have been discussed based on the solution.
2、The microstructure, mechanical property, and inner stress in different cold deformation mode are researched. Different deformation mode has a big effect on work hardening, and the work hardening coefficient is 2.8, 2.5 for drawing with die, and drawing with plug respectively. Different cold deformation mode influence the magnitude and distribution of inner stess, too.
3、Different cold deformation mode has a different recovery kinetics process when annealing at the low temperature. The recovery velocity of tube drawing with plug is faster than the tube drawing with die, and the kinetics parameter of the former is ,and the latter is .
4、The paper pay attention on the recrystallization grain size of cold deformation tube. As the increasing of effective strain, grain size of recrystallization firstly increase, and then decrease. The critical cold drawing reduction for the largest recrystallization grain size decrease as the annealing temperature was increased. For the tube of drawing with die, the critical effective strain is 5～32×10-2 ( 2％～15％). When the effective strain is over 0.5(or 20％), the abnormal recrystallization grain growth doesn`t appear in any annealing temperature. For abnormal grain growth(AGG), the grain size is 5-20 times more than that of the normal grain growth.
5、There will appear large grains with sizes of several hundreds microns when the samples are annealed at a certain deformation strain and temperature. For example, the grain size is 300μm when the deformation strain is 5.19×10-2 and the annealing temperature is 550℃ and the annealing time is one hour in the drawing tube with die. The other example is that the grain size is 800μm when the deformation strain is 7.17×10-2 and the annealing temperature is 550℃ and the annealing time is one hour in the drawing tube with plug.
6、The recovery before recrystallization can`t eliminate the abnormal grain growth. However the thorough recovery before recrystallization for the tube drawing with die can fine the grain size after annealing treatment.
7、After annealing treatment at the temperature more than 440℃, the hardness of the samples increase as the annealing temperature increase. Through measurement of the mechanical properties of various heat-treated cold-drawed tubes, matched with many methods, for example, quantitatively optical observation, SEM, EDX, etc., the relationship of the microstructure of tubes and the mechanical properties was obtained. The solution strengthing of Mg in Al crystal lattice results in the increasing of hardness. |
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