In this research, the multi-pass friction stir processing on AZ91 alloy has been simulated with the three-dimensional numerical modeling based on the ABAQUS/ Explicit. This simulation involves the Johnson-Cook models for defining the material behavior during this intense plastic deformation and investing the fracture criterion. Friction stir processing is a complex process that includes several issues such as high strain rate deformation, microstructure evolution, the asymmetric flow of material, and heat. Therefore, the modeling of this process is challenging. This model simulates the tool plunging and stirring phases in the two-pass process. In this paper, to prevent too much damage in the elements during processing, the Arbitrary Lagrangian-Eulerian technique for automatically remeshing of distorted elements has been used. This work shows that the numerical modeling can be an efficient method to study the effect of process parameters on the thermal evolution and the stress distribution. The thermal model was calibrated using the experimental results from the previous works. This model can predict the transient temperature distribution and residual stress field during FSP on AZ91. The results show that the maximum temperature in the advancing side is more than that in the retreating side. In addition, numerical results show that at the end-position of the process, the tool during the lift-up leaves the keyhole region in a compressive stress state. Manuscript profile

The attractive mechanical properties of 7075 alloy, such as its high strength-to-weight ratio and fracture toughness, have received special attention in the automotive and aerospace industries. However, welding as a fabrication process has a detrimental effect on this alloy’s properties which affects its mechanical performance. In this work, to compensate for the loss in mechanical properties caused by welding, proper heat treatment operations are adopted. To this end, 1.5 mm AA7075 sheets were first preheated and butt welded using the gas tungsten arc welding process. The welded sample was solution heat treated, quenched, and then artificially aged. Microhardness tests showed an increase of hardness in all zones of the aged specimen compared to those of the original welded blank before heat treatment. A maximum microhardness value of 180 HV was recorded in the heat-affected zone of the aged specimen. In addition, elongation at break, and strength (yield, tensile, and fracture) of the original welded blank increased by about 50% after the artificial aging operation. Manuscript profile