Simulation of Friction Stir Processing with Internally Cooled Tool

Abstract

Friction stir processing (FSP) is considered to be a promising sustainable technique for grain refinement of metallic alloys. The heat generated during FSP promotes dynamic recrystallization in processed material which is essential for grain sub-division process. However, excessive heat generation can lead to high temperatures of >300°C that may cause abnormal grain growth in the processed material. On the other hand, repetitive high temperature heating cycles can reduce the lifetime of the FSP tool. Therefore, it is essential to manage the process heat not only to achieve homogeneity and finer grain sizes in the processed material but also to reduce tool wear. In this work, friction stir processing of AZ31B Mg with an internally cooled FSP tool is simulated by a three-dimensional CFD model. We have studied the effect of rapid tool cooling on temperature and flow stress distribution in processed material. Additionally, the grain size and hardness of the processed material is estimated by using Zener-Holloman and Hall-Petch based relationships. It was found that FSP with internally cooled tool is a promising approach that effectively controls temperature levels during processing. Therefore it enables the achievement of better mechanical properties by effective grain refinement and has a positive effect on tool life.

Superplastic Forming Response of a Friction Stir Processed Mg Alloy Sheet – A Numerical Approach

“…CFD analysis of FSP is carried out to study the effects of processing parameters, such as tool rotational and translational speeds, on temperature fields, flow stresses, and microstructure evolution. For the sake of brevity, the discussion here will be limited to grain size prediction, more details can be found at [6]. The average recrystallized grain size in stirred and transition zones of the processed sheet is evaluated from temperature and strain rate fields using Zener-Holloman relation.…”

“…The purpose of this model is to predict the grain size after processing, starting from the as received microstructure. More details about the model can be found in [6]. In this model the sheet is assumed to behave as a non-Newtonian highly-viscous fluid.…”

Microstructure, hardness, and wear resistance of AZ91 magnesium alloy produced by friction stir processing with air-cooling

“…The authors found that the microstructures of all the samples were characterized by fine equiaxed grains in the stirring zone, but the greatest elongation of the samples was achieved for the CO 2 -cooled sample due to the lowest heat input during FSP. In turn, in [32], friction stir processing of the AZ31B magnesium alloy was performed using an internally cooled FSP tool. The authors found that the applied solution allowed effective temperature control during processing, which leads to improvement of the mechanical properties through effective grain refinement and has a positive effect on the tool life.…”

Microstructure, hardness and wear resistance of AZ91 magnesium alloy produced by friction stir processing with air cooling

“…The authors found that the microstructures of all the samples were characterized by ne equiaxed grains in the stirring zone, but the greatest elongation of the samples was achieved for the CO 2 cooled sample due to the lowest heat input during FSP. In turn, in [32] friction stir processing of the AZ31B magnesium alloy was performed using an internally cooled FSP tool. The authors found that the applied solution allowed effective temperature control during processing, which leads to improvement of the mechanical properties through effective grain re nement and has a positive effect on the tool life.…”