Study of Corrosion, Structural, and Mechanical Properties of EN AW-6082 and EN AW-7075 Welded Joints.

Tomasz Wojdat,Karol Jaśkiewicz,Paweł Kustroń,Jarosław Pabian

doi:10.3390/ma14164349

Abstract

The purpose of the work was to test the welded joints of aluminum alloys EN AW-7075 and EN AW-6082, which are used to join individual structural elements of car bodies, e.g., B-pillar with the body. The joints were made using the low-energy cold metal transfer (CMT) arc welding method. The results of the structure investigations of lap and butt joints, as well as tests of mechanical properties are presented. The influence of linear energy and the way of arranging materials in lap joints on the possibility of hot cracks occurrence has been demonstrated. The shear strength of lap joints was equal to 150 MPa, while the tensile strength of butt joints was equal to 375 MPa. The highest hardness reduction was observed in the heat affected zone (HAZ) from the EN AW-7075 alloy side in the range of 98 to 138 HV 0.05. In addition, a significant reduction of the corrosion resistance in the transition zone between HAZ and the base material (EN AW-7075 alloy) in the medium salinity environment, corresponding to the sea conditions according to ASTM G85 was indicated.

Highlights

The application of aluminum alloy sheets in the construction of car bodies is more and more common. This is, European, and a global trend caused by newly introduced directives and pro-ecological regulations, including, e.g., reduction of CO2 emissions [1] and other contaminants (HC, NOx, PM, and particulate matter) coming from the combustion of fuels in gasoline and diesel engines [2]
The low magnification observations of samples was done by scanning light microscope Keyence VHX1000 (Keyence, Osaka, Japan)
The visual tests carried out after the welding process showed a significant amount of small spatters in the welding zone very close to the weld (Figure 2a)

Summary

Introduction

The application of aluminum alloy sheets in the construction of car bodies is more and more common. This is, European, and a global trend caused by newly introduced directives and pro-ecological regulations, including, e.g., reduction of CO2 emissions [1] and other contaminants (HC, NOx, PM, and particulate matter) coming from the combustion of fuels in gasoline and diesel engines [2]. For example, the B-pillar which rather than steel, can be made of highstrength aluminum alloy EN AW-7075 [3] Applying such a solution, causes considerable difficulties in assembly technology, especially in welding methods. This alloy has very limited weldability, which excludes the possibility of using conventional welding methods [4]

Objectives

Discussion

Conclusion