چكيده به لاتين
Heat treatment is widely used on aluminum alloys as one of the effective methods to improve the mechanical properties and microstructure of materials. Since most of these operations in aluminum alloys are time-consuming and make artisans face many problems in the field of production with higher efficiency, this research examines the solution to this problem. It also follows the improvement of tensile properties and the increase of hardness in 6061 aluminum alloy. Accordingly, in this project, an infrared furnace with a rapid heating rate characteristic was used for the heat treatment of this alloy, which provides an increase in the entropy of the dissolved atoms during the solution process, which, according to thermodynamic and metallurgical relationships, increases the driving force for the formation of precipitation and the rate of nucleation during the aging process.
Therefore, with T6 heat treatment on 6061Al (Al-Mg-Si) alloy with heating rates of 0.3 and 2 degrees Celsius/second, which are related to resistance and infrared furnaces, respectively, the effect of rapid heating on the tensile properties and hardness of 6061Al alloy was investigated. All these operations were done with solution temperature of 530 ͦ C and aging temperature of 180 ͦ C and quench with water, and only the time of each process was changed and tested in the samples. The hardness of the aged sample was measured in the resistance furnace with the conventional heat treatment cycle in the industry (solution time 60 minutes and aging time 8 hours), 105HV. Also, the ultimate strength, yield strength, and absorbed energy before failure of this sample were estimated as 293.7, 254 MPa, and 48.92 kJ, respectively, and its elongation was estimated as 17.8%. But the hardness of the sample aged in the infrared furnace was measured as 110.6 HV with a solution time of 40 minutes and an aging time of 2 hours. Also, the ultimate strength, yield strength, and absorbed energy before failure of this sample were estimated as 297.51, 250 MPa, and 50.54 kJ, respectively, and its elongation was estimated as 17%. These results were obtained while the total heat treatment time in the resistance furnace is 3.37 times the total heat treatment time in the infrared furnace. Also, by examining and analyzing the SEM images of the heat treated sample in the resistance furnace by Imagej software, the number, average area size and approximate volume percentage of the precipitation formed in the matrix after aging were calculated as 288, 0.08 square micrometers and 1.69%, respectively. Meanwhile, the number, average size of the area and approximate volume percentage of the precipitation formed in the matrix of the heat treated sample in the infrared furnace after aging were estimated to be 409, 0.1 square micrometer and 3.22%, respectively.
