Impact of flat-surfaced pins on material flow and particle distribution in friction stir processing: a CEL method analysis

Abstract

This study examines the impact of pin profile geometry on temperature, strain, particle distribution, and material flow through a Finite Element Method (FEM), which utilizes a Coupled Eulerian-Lagrangian (CEL) formulation and effectively is capable of predicting temperature, strain, and material flow during Friction Stir Processing (FSP). A comparison between experimental and numerical results regarding the distribution of reinforcing particles in the base metal reveals a strong correlation, highlighting the model's capability to accurately forecast material flow patterns. The findings indicate that the circular tool was ineffective in achieving a uniform distribution of particles, as a substantial number accumulated at the center of the sheet. In contrast, the square and hexagonal tools exhibited superior performance in terms of particle distribution. This can be attributed to the design of their pin profiles, in which flat surfaces generate a pulsating effect, thereby enhancing material flow. Moreover, in samples processed with square and hexagonal pins, particles located near the top surface of the plate spin with the pin and are subsequently stretched towards the advancing side, despite in the circular pin a significant number of particles accumulated in the center of the sheet. As a result, the square and hexagonal tools exhibit higher average hardness values of 68.88 HV and 66.84 HV, respectively, in comparison to the circular tools, which have an average hardness of 57.17 HV.