Keywords

Abstract

Friction stir welding; 

Microhardness;

 Impact toughness;

 Response surface methodology;

 Central composite design

This study aims to develop mathematical models that can predict the characteristics related to mechanics, such as microhardness and impact resistance, of Aluminum that has been friction stir-welded 8006 alloy joints with 95% confidence. The four process parameters tool tilt angle, welding speed, tool pin shape, and rotating speed were systematically varied across three levels. Following a response surface and central composite design approach that is face-centered, the influence of different factors on the mechanical properties of aluminum 8006 alloy joints was assessed. The highest impact toughness of 58 joules was observed in joints specially prepared by a cylindrical threaded pin profile tool with a 1° tilt angle operating at 800 RPM and a feed rate of 20 mm/min and test was conducted at room temperature. Additionally, it was investigated how process factors affected impact toughness by ANOVA and the results revealed that the tool pin geometry is identified as the most significant process variable on impact toughness, contributing 52.52%, thereafter the tool tilt angles (15.53%), rotating speed (8.80%), and welding speeds (5.84%). The findings showed that, for impact toughness, the tool tilt angle and pin shape were more important than welding speed and tool rotation speed, but the tool pin profile and the welding speed showed governance over rotational speed and angle of tilt in case of hardness. The joints achieved a maximum hardness of 166 VHN at stir zone of the welded specimen made from a threadless taper pin tool for the speed of 1200 rpm, the tool was tilted at 2 degrees while welding at a speed of 40 mm/min. Finally, the effects of process parameters on the microstructure of friction stir welded Aluminum 8006 alloys were addressed and discussed.

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