Microstructure-Bendability Relationship in V-Bending of Cast Aluminum Alloy A356

Cast aluminum alloys provide interesting microstructures with a large number density of second phase particles that act as potential sites for damage initiation and development. Therefore, fundamental studies related to the role of second phase particles on deformation behavior can be easily carried out. However, the challenge lies in the observation and characterization of damage during the deformation process.In the present work, the effect of microstructure on bendability of an automotive cast aluminum alloy A356 has been studied under V-bending loading. In-situ V-bend tests are carried out inside a scanning electron microscopy (SEM) while recording high magnification images of the through-thickness region of the bend to determine aspects of strain localization and particle induced damage in the microstructure. In addition, the initial microstructure is utilized as a speckle pattern for further analysis of through-thickness strain development in the bent region via digital image correlation (DIC) method. This method utilizes digital images of progressive deformation of specimen to obtain displacement and strain fields. The above methodology is applied to unmodified and Sr-modified A356 compositions. The results indicate superior bendability of Sr modified A356 alloy compared to the unmodified alloy. The differences in bendability are attributed to the morphology of the second phase particles in the two cast alloys and its effect on the deformation and damage mechanisms during bending. The findings are consistent with uniaxial tensile elongation of the two alloys. Also, the results demonstrate that insitu SEM bending coupled with DIC based strain analysis offers a useful method of analyzing the effect of microstructure on bendability of cast materials.