Mechanical Properties and Microstructures of Commercial‐Purity Aluminum Processed by Rotational Accelerated Shot Peening Plus Cold Rolling

Abstract

Commercial purity aluminum with 99.7% purity was processed by rotational accelerated shot peening (RASP) and cold rolling. RASP samples were rolled at room temperature to a thickness reduction of 20% and 30%, for the purpose of surface roughness reduction and strengthening. Detailed microstructural characterization and hardness tests revealed that cold rolling caused grain growth at the surfaces of RASP samples from ~472 nm to ~1000 nm. Moderate cold rolling is effective in smoothing the surface of RASP samples, while improving strength and maintaining ductility. However, cold rolling to more than 30% thickness reduction will eventually diminish the gradient nanostructure. During cold rolling of RASP samples, a transition zone with strong strain incompatibility was noticed by a sharp rise in hardness at some point of the hardness distribution curve from the surface to the core of the sample. This transition zone was a result of quick generation of geometrically necessary dislocations. Although, the transition zone with strong strain incompatibility is short lived, it is anticipated to be common among gradient-nanostructured materials under cold rolling condition.

Effective Surface Nano-Crystallization of Ni2FeCoMo0.5V0.2 Medium Entropy Alloy by Rotationally Accelerated Shot Peening (RASP)

“…Once the nano-crystalline layer is formed, the material’s surface is significantly hardened. The RASP-imposed shear stress decreased drastically when it transmitted through the hard nano-crystalline layer [ 52 ]. Thus, only a thin layer of a few tens of nanometers below the nano-crystalline layers experienced a high shear stress, which was just sufficient to activate deformation twinning.…”

Nano-Gradient Materials Prepared by Rotary Swaging

“…Moreover, the residual stress also has an effect on strength. References [43] point out that the strength dis- Interestingly, according to previous literature, there are three different hardness/strength distributions observed in the cross sections (top view) of RSed rods: (1) V-shaped distribution [40,43]-the strength of edge is higher than that of the center; (2) uniform distribution [64]-the strength of edge is basically equal to that of the center; (3) Λshaped [41,50,65]-the strength of edge is lower than that of the center. Fortunately, these hardness distributions are detected in the Cu rods with various strains.…”

Phase Transformation-Induced Improvement in Hardness and High-Temperature Wear Resistance of Plasma-Sprayed and Remelted NiCrBSi/WC Coatings

“…Therefore, it is necessary to improve their wear resistance in such environments. Generally, surface modification methods for improving wear resistance include thermal spraying [2][3][4], laser processing [5][6][7][8], friction stir processing [9,10], micro-arc oxidation [11], shot peening [12,13] and so on. Among these methods, thermal spraying is an efficient technology to produce reliable coatings on the workpieces [14].…”