چكيده به لاتين
This research investigates the effect of the accumulative roll bonding (ARB) process and precipitation hardening process on the microstructure and mechanical properties of Al-Ag-sc Alloy due to its unique properties, such as casting. Al-Ag-Sc alloys, due to their ability in heat treating and precipitation hardening and suitable mechanical properties, are considered to be one of the essential and widely applicable alloys in strategic industries.Aging heat treatment and ARB are the main strengthening methods used in aluminum alloys. Combining these methods leads to more strengthening, known as thermomechanical operation. This research investigates the effect of ARB and precipitation hardening process on the microstructure and mechanical properties of Al-Ag-sc Alloy. The specimens were annealed for 24 hours at 600 C for this task; then, they were cooled to room temperature inside a furnace. For two-step precipitation hardening, the specimens were first kept for 5000 seconds at 350 C and quenched in water. The specimens were heated to 250 C for 5000 seconds for the second step and then quenched in water. Finally, eight passes of ARB were conducted on the specimens.
SEM, OM, and hardness tests were used for mechanical and microstructural analysis. Structural alteration of specimens was measured by XRD and EDS analysis. Specimens' mechanical properties were examined by tensile, wear, and micro hardening tests during different passes of ARB. Moreover, a slight degree of annealing at 150 and 250 C in an oven with an air atmosphere were conducted. Then, the effect of slight annealing on the specimens' microstructure, mechanical properties, and fracture surface was studied. An SEM Microscope was used to examine the quality of cold bonding in ARB. Microstructural parameters such as crystallite size, microstrain, and dislocations density on the sheets were calculated using the RithWeld*** method. After the tensile test, the specimens' fracture surfaces were examined by an SEM, and the results illustrated suitable rolling joints between the layers except in the last cycle.
Additionally, the size of the crystallites showed that the samples were fine-grained with increasing ARB cycles. The mechanical test results showed that after 4 cycles, the tensile strength and stiffness reached 4 and 3.8 times that of the annealed samples, respectively. At the same time, the elongation increased slowly and reached 8% in cycle 8. The cross-sectional area of the microscopic fracture of the specimens consisted of deep, coaxial dimples, indicating a soft fracture. As the cycles increased, the diameter and depth of the dimples decreased, and the soft fracture gave way to the soft shear fracture. After the partial annealing process, the strength decreased slightly in the first cycle and significantly decreased in the subsequent cycles.
