Effect of heat treated alloys in deformation
Abstract: through solid solution treatment, cold rolling and subsequent aging treatment of cu-1.0 cr-0.2 Zr alloy, the influence of deformation and aging process on mechanical properties, electrical properties and structure of materials was studied. The results show that the alloy has a strong aging effect. Pre-cooling deformation before aging can significantly improve mechanical properties of cu-1.0 cr-0.2 Zr alloy and maintain high electrical conductivity. The tensile strength and yield strength of the alloy reached 527.0 and 487.0mpa, respectively, with a elongation rate of 12.3% and a conductivity rate of 82.0%IACS under the optimal deformation heat treatment process. The improvement of mechanical properties of alloy and slight decrease of electrical properties are mainly controlled by three factors: dissolution of solid solution during aging process, recovery and recrystallization of matrix, and precipitation of new phase. Among them, precipitation of fine and uniform distribution is an important influencing factor for obtaining high mechanical and electrical properties.
The main composition of the experimental alloy is cu-1.0 cr-0.2zr. Slab specimens, is the basic process of solid solution 2 at 960 ℃, the water quenching and aging at room temperature before cold deformation. Some reference to previous research results [19-21], aging temperature range as 430 ~ 530 ℃, cold deformation range of 20% ~ 80%, aging time as the first 4 h. Firstly, optimize the aging temperature within the aging temperature range, then further optimize the aging time under the optimized aging temperature, and finally optimize the influence of cold deformation on the aging process on the optimized aging temperature and time.
The sample size and processing of the plate after aging heat treatment shall be conducted according to the national standard, with a marking distance of 40 mm and a drawing speed of 2 mm/min. Tensile test was conducted on the css-44100 universal electronic tensile testing machine. The conductivity test first measured the resistance value of the single-arm bridge in QJ19 and then converted to conductivity. The metallographic sample grinding surface was taken from the rolled surface of the plate, and optical metallographic analysis was carried out on the PLOYMAR MET microscope. The samples were ground and polished for chemical corrosion. The corrosion solution was hydrochloric acid solution of FeCl3. The microstructure of the alloy with the best properties during the deformation heat treatment was observed and analyzed by JEOL 2001 high resolution electron transmission electron microscope.
2 results and analysis
2.1 effects of solid solution - cold deformation - aging process on alloy properties
After hot-rolled annealed plate is treated with solid solution-cold deformation-aging process, the mechanical properties and electrical properties of the alloy are obtained under different aging processes.
At 960 ℃ solution 2 h and 4 h under the condition of limitation of different aging temperature on the influence of alloy mechanical properties and electrical conductivity. When temperature above 430 ℃ ageing, alloy of high tensile strength and yield strength to ascend, and 450 ℃ when the alloy tensile strength and yield strength of the peak, then with the increase of aging temperature tensile strength and yield strength of the alloy and falling rapidly, alloy has a strong limitation to strengthen effect. Meanwhile, the conductivity of the alloy increases with the aging temperature.
Under the 450 ℃ ageing temperature, different aging time on the mechanical properties of the alloy and the influence of the conductivity. It can be seen that the mechanical properties of the alloy first increase, reaching the peak value at the time of 4h aging, and then continuously decline with the extension of the aging time, while the conductivity increases with the extension of the aging time, but the increasing trend slows down and finally reaches the constant value. Visible, from the analysis of above 450 ℃ ageing 4 h is better aging treatment system, in this system, alloy tensile strength and yield strength of the peak, the electrical conductivity of alloy at high levels.
Under the condition of 450 ℃ ageing 4 h, of different cold deformation before aging on mechanical properties of alloys and the influence of the conductivity. Under the same aging process conditions, the strength of the alloy increases with the increase of cold deformation, while the conductivity decreases after reaching the peak value. This is because the increase of cold deformation before aging leads to the increase of dislocation, vacancy proliferation and crystal interface area. Meanwhile, a large number of dislocation and other defects increase the deformation energy storage of the alloy, and the precipitated phase is more sufficient and the enhancement effect is increased, so the strength of the alloy increases. When the deformation reaches 80%, the influence of defects and interfaces on the conductivity exceeds that of solute atoms on the conductivity, leading to a decline in the conductivity. However, the defects such as dislocation and vacancy caused by deformation have little effect on the conductivity of the alloy. When the preaging cold deformation is 70%, the conductivity of the alloy still reaches 79.87%IACS, maintaining a high conductivity.
1) Cu-1.0Cr-0.2Zr alloy has strong aging effect. As the aging temperature increases and the aging time increases, the precipitated phase grows and the alloy strength decreases. However, with the constant dilution of solid solution in the aging process, the electron scattering decreases, and the conductivity increases and remains at the level of a platform.
2) deformation heat treatment can improve mechanical and electrical properties of cu-1.0 cr-0.2 Zr alloy. Alloy solid solution by 60% after 2 h at 960 ℃ 450 ℃ cold deformation and aging 4 h, tensile strength, yield strength and elongation of the alloy is 527.0 MPa, 487.0 MPa and 12.3%, respectively, the relative conductivity of alloy is 82.0% IACS.
3) Cu - 1.0 Cr - 0.2 - Zr alloy after 60% cold deformation 450 ℃ ageing 4 h, alloy for two kinds of fine dispersed distribution of precipitation phase. The stapling of the precipitate to the dislocation slows down the process of deformation recovery and subsequent recrystallization. The dispersion of fine precipitated phase is an important mechanism of alloy strengthening.