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An Investigation on the Effects of Cyclic Quench-Rolling on the Mechanical Properties and Formability of a 7000 Series Aluminum Alloy

Farmani, Mohammad Reza | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56192 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Karimi Taheri, Ali; Serajzadeh, Siamak
  7. Abstract:
  8. Nowadays, Thermomechanical processes are used to change the microstructure and create desirable mechanical properties in metals. In this research, with the aim of improving the mechanical properties and formability of 7000 series aluminum alloys, the Cyclic Quench-Rolling (CQR) process was designed and investigated as a new thermomechanical process with solid solution strengthening mechanism. First, for solution heat treatment, the 7075-T6 aluminum sheet was placed in the oven at 460 °C for 5 hours and quenched in water. After making the solid solution, in each cycle of CQR, a rolling step was performed, then intermediate solutioning heat treatment and then quenching was performed. To study the effect of different parameters on this process, tests were carried out at intermediate solution temperatures of 280, 370 and 460 °C, for a period of 5, 15 and 30 minutes, in the quenching environments of 25 °C water and oil, with a rate of change of form of 10, 20 and 30% in each cycle, with a final strain of 40%, 67% and 84% in variable number of cycles. To determine the mechanical properties and formability of the samples produced by CQR, uniaxial tensile test, hardness test, Erichsen formability test, metallographic and scanning electron microscope (SEM) images and X-ray diffraction analysis were performed. According to the results, a sample was produced under optimal production conditions and aged at 180°C for 24 hours in order to achieve more stable properties. The final strength and elongation percentage of the optimal sample produced after aging reached 624 MPa (54 MPa more than the as receive sample) and 11.12% (about twice the as receive sample), respectively. As a result of this process, the microstructure of the sample was transformed into a collection of fine grains resulting from recrystallization in heat treatment cycles and elongated coarse grains resulting from rolling. After aging a homogeneous and fine distribution of the strength phase particles was obtained. Also, due to the simultaneous increase in strength and length, the formability of the sample also increased
  9. Keywords:
  10. Solid Solution ; Aluminum Alloy 7075 ; Thermomechanical Processing ; Erichsen Test ; Cyclic Deformation ; Aluminum Alloy Series 7xxx

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