Metallography and Mechanical Properties of Al5083 Sheets Processed Through Peen Forming

Abstract

Peen forming is a die less forming process performed at room temperature. During the process, the surface of the work piece is impacted by pressure from small, round steel shot. Every piece of shot impacting the surface acts as a tiny hammer, producing elastic stretching of the upper surface. The impact pressure of the peening shot causes local plastic deformation that manifests itself as a residual compressive stress. The surface force of the residual compressive stress combined with the stretching causes the material to develop a compound, convex curvature on the peened side.

In the current project, As Al5083 is a corrosion resistance and non-heat treatable alloy, is chosen to deform through shot peening. The 0.5mm thickness sheet with length of 150mm and width of 60mm is placed in a Los Angles abrasive machine. 240gms of Steels balls (Six balls each weighing 60gms) were used for imposing impact load to compress the sheets during peening. The process is carried out for 100, 200 and 300 revolutions for 3minutes, 6minutes and 9minutes. The shot peened deformed sheets were tested for area and hardness to study the amount of deformation and strength. As the number of revolutions increases the area of the deformed sheets decreases, the hardness of deformed sheets increases with increase in no. of revolutions. The microstructure through optical microscope reveals the formations fine grains during peening. Highest hardness of 72HRB is found for 300 revolutions sheets during cold working of shot peening. The tensile specimens were prepared according to ASTM E-8 standards the strength increases from 285MPa to 325MPa with increase in no. of revolutions through shot peening.