HFQ forming of AA6082 tailor welded blanks

Jun Liu,Liliang Wang,Haoxiang Gao,Omer El Fakir,Jianguo Lin,Y Qin,S J Yuan,J Lin,F Vollertsen,T A Dean

doi:10.1051/matecconf/20152105006

Abstract

An advanced forming technology, solution Heat treatment, Forming and in-die Quenching (HFQ ® ), has been employed to form AA6082 tailor welded blanks (TWBs). In comparison with conventional stamping of TWBs, the mechanical properties and formability of AA6082 laser TWBs could be improved under the HFQ forming condition. The TWB was divided into three physical zones, i.e. base metal, heat affected zone (HAZ) and weld zone, based on the hardness distribution. It was found that the degraded hardness of the weldment can be restored after HFQ forming. TWBs of AA6082 with different thickness ratios of 2 (2-1mm), 1.3 (2-1.5mm) and 1 (1.5-1.5mm) were used to study the TWB thickness ratio effects on the forming behaviour. Hemispherical punch dome tests on the TWBs with varying thickness ratios demonstrated different formabilities, and indicated increased displacement of the weld line with increasing thickness ratio. Finite element (FE) modelling was adopted to analyse the weld line movement and strain distributions during HFQ forming. HFQ ® is a registered trademark of Impression Technologies Ltd.

Highlights

In recent decades, aluminium alloys have attracted the attention of many researchers, engineers and designers as promising structural materials for the automotive industry applications
The limit dome height (LDH) increases with the decreasing blank thickness ratio and increases as the forming speed increases from 75 to 400 mm/s, the increasing trend for the 2–1 mm tailor welded blanks (TWBs) is not as significant as the 1.5– 1.5 mm TWBs
The premature fracture occurred at higher blank thickness ratios, because the localised strain primarily occurred in the thinner blank at higher circumferential stress levels

Summary

Introduction

Aluminium alloys have attracted the attention of many researchers, engineers and designers as promising structural materials for the automotive industry applications. As a commercial alloy with high stiffness to density and high strength to density ratios, AA6082 is suitable for structural sheet-metal fabrications. Tailor welded blanks (TWBs) consisting of multiple sheet materials joined with welds has been widely used in lightweight structures. The market for aluminium alloys is expanding into various sectors, most significantly in automotive industries where the use of tailor welded blanks in aluminium is developing rapidly. Due to the development of advanced forming technologies, it is possible to form tailor welded blanks to produce body panels with complex structure and reduced weight [1]. The most commonly used welding technology for manufacturing the AA6082 tailor welded blanks is laser beam welding. Laser welding has various advantages, including high productivity, high weld quality in terms of controllable heat affected zone (HAZ) and weld zone, low distortion, flexibility due to the movable heat source, reliability and precision [2]

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