Evolution of Microstructure and Mechanical Properties in a Single-Stage Aged 7075 Aluminum Alloy Pulse Variable Polarity Plasma Arc Welded Joint

Guowei Li,Yongquan Han,Yahong Liang,Li Sun,Furong Chen

doi:10.3390/met9040428

Guowei Li, Yongquan Han + Show 3 more

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https://doi.org/10.3390/met9040428

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Journal: Metals	Publication Date: Apr 10, 2019
Citations: 6	License type: CC BY 4.0

Affiliation: Inner Mongolia University of Technology

Abstract

A 7075 aluminum alloy was successfully welded by pulsed variable polarity plasma arc welding (PVPPAW) and the single-stage aging behavior of the 7075 aluminum alloy PVPPAW joint was systematically investigated. The results demonstrated that the tensile strength of the welded joints initially increased and then decreased with the increase of the single-stage aging temperature and time. After single-stage aging at 490 °C for 80 min and at 130 °C for 24 h, the tensile strength of the welded joint was 551 MPa, which was increased by 38.5% compared to the as-welded joint. Moreover, the conductivity was 25% international annealed copper standard (IACS) at room temperature, and the resistance to stress corrosion was improved. The main strengthening phases of the weld center were η′ and η phase. The average precipitate size slightly increased with the increase of the single-stage aging temperature, but no obvious change was observed with the increase of the single-stage aging time. The area fraction was initially increased and then decreased with the increase of the single-stage aging temperature and time.

Highlights

Due to their excellent mechanical properties, 7××× series high-strength aluminum alloys are widely used in aerospace, national defense, navigation, automobile, and other fields [1,2,3,4,5,6]
A VPPA-300 welding power supply and a PMW-300 plasma arc welding torch were used in the experiments, the welding equipment is shown in Figure 1, while 99.9% argon gas was used as both plasma and shielding gas
A 7075 aluminum alloy was welded by pulsed variable polarity plasma arc welding (PVPPAW) using ER5183 (Al-Mg alloy)

Summary

Introduction

Due to their excellent mechanical properties, 7××× series high-strength aluminum alloys are widely used in aerospace, national defense, navigation, automobile, and other fields [1,2,3,4,5,6]. Compared to other traditional fusion welding techniques, PVPPAW technology has significant advantages in welding aluminum alloys [9,10,11], such as the small deformation, energy concentration, absence of a need for groove preparation, narrow weld bead, one-sided welding, and both sides formation. There are some limitations, including the strength loss and poor corrosion resistance of welded joints [12,13], which affect, to a certain extent, the further development and application of the Al-Zn-Mg-Cu aluminum alloy

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