Formability of Tailored hybrid blanks

Abstract

Tailor Welded Blanks (TWB) characterized by the fact that sheets with different material qualities and/or thicknesses welded together before forming process. The application of TWBs in the automobile industry brings several advantages, for instance, reduction of car body weight, reduction of manufacturing costs and integration of several drawing parts into one part. Despite several established tailor welded blanks types, a new version has emerged the Tailored Hybrid Blanks (THB). Unlike steel TWBs, the challenges in connecting steel and aluminum by a conventional welding method are, on the one hand, the different physical characteristics such as density, melting temperature, electrical conductivity and thermal expansion. On the other hand, due to high heat input a thick, very hard and brittle intermetallic phase seam (IMP) develops in the weld seam. This strongly distinctive phase seam reduces the formability of the welding line. Therefore this limits the realization in technical applications. The current investigation focuses on tailored hybrid blanks joined by the CMT-welding technology. The main aim of this study is to specify the forming ability of Aluminum Steel tailored blanks. Steel (HC340LA, 0.8 mm) blank sheets combined with an Aluminum alloy (AA6014-T4, 1.2 mm). Nakajima tests with online deformation analyses shows that the main formation takes place on the Aluminum side. All specimens in the tensile test failed beyond the HAZ in the Aluminum. In particular, the weld line has the tendency to move during the forming operation toward the direction of the steel. In the cup test, the deep-drawing ability improved by introducing recesses on the tool.