Improvement of Weldment Properties by Hot Forming Quenching of Friction Stir Welded TWB Sheet

Abstract

The purpose of this study is to improve the mechanical properties and formability of friction stir welded tailor-welded blanks (TWBs) of Al6061 alloy with a new forming method called hot forming quenching (HFQ) in which solid-solution heat-treated aluminum sheets are formed at elevated temperature. Forming and quenching during HFQ are simultaneously performed with the forming die for the solid-solution heat-treated sheet. In this study, specimens of aluminum TWBs were prepared by friction stir welding (FSW) with a butt joint. The effectiveness of FSW joining was evaluated by observation of the macrostructure for different sheet thicknesses. In order to evaluate the formability of TWBs by HFQ, a hemisphere dome stretching test of the limit dome height achieved without specimen failure was performed with various tool temperatures. A Vickers test was also performed to measure weldment hardness as a function of position. The formability and mechanical properties of products formed by HFQ are compared with those formed by conventional forming methods, demonstrating the suitability of HFQ for sheet metal forming of friction stir welded TWBs.

Friction stir welding of aluminium alloys: An overview of experimental findings – Process, variables, development and applications

“…A tilt angle of 1 to 3 is advisable. 50,[96][97][98][99] Greater tilt angles tend to lift the bottom of the pin from the root of the weld thereby decreasing the target depth leading to insufficient stirring at the root causing defects at the root of the weld. The effect of various variables/combination of variables on the weld quality of different aluminium alloys has been reported by many researchers.…”