Investigation of the effects of shallow-cryogenic and agingheat treatments on microstructure, hardness and naturalfrequency properties applied to AA2024, AA6061, AA7075 Al alloys

Daha sonra doldurulacaktır.Aluminum (Al) and its alloys are materials that are widely used in many industrial areas in terms of their low specific gravity, corrosion resistance and strength properties. Thanks to its properties, Al and its alloys have begun to replace the materials used in the past in the industry. Although the lightening of the designs and the preservation of their strength properties are interesting in the field of industry, the mass lightening of the designs can be caused by heat, cold and pressure etc. It triggers the natural frequency value that occurs as a result of excitation of materials under different environmental conditions. It is known that materials are constantly exposed to different frequencies by external stimuli according to the working area, and the resonance effect that occurs as a result of the coincidence of the different frequencies exposed and the natural frequency value of the materials can damage the material. This study produced AA2024, AA6061 and AA7075 Al alloy plates with 2 mm thickness by cutting samples with different cross-sectional areas between 0° and 1° with a 0.1° increase rate. The heat treatment process was applied to the test samples with different cross-sectional areas produced under two different conditions. The first heat treatment process applied in the study; Thawing at 510°C for 2 hours + quenching + aging at 160°C was applied. In the second heat treatment process applied; Test samples were obtained by thawing at 510°C for 2 hours + quenching + 168 hours shallow-cryogenic cooling at ≈ -75°C + aging heat treatment at 160°C. At the end of each applied step, the hardness properties and natural frequency values of Al alloys were analyzed. In line with the data obtained, two heat treatment processes, which include heating and cooling processes applied to Al alloys, and the effects of samples with different cross-sectional areas on the natural frequency value were investigated. The study applied Optical Microscope, FESEM, EDS and XRD analyses to the samples for characterization after and before the heat treatment. Thanks to the study, the effects of Al alloys on the natural frequency value in cold, hot environments and room temperatures were examined in detail by examining the improvement of the hardness properties of Al and its alloys in many engineering sectors, especially in the aviation sector, and their natural frequency properties.