Abstract
The precipitation-hardenable aluminum alloy 6061 (AA 6061) is favored for aerospace components and automotive parts. However, the tenacious oxide layer on the surface greatly limits the quality and applicability of joining AA 6061. In this study, the joining method of solid-state diffusion bonding was implemented for AA 6061 plates, and the effects of post-weld heat treatment (PWHT) on the joint interface were investigated. The bonding temperatures were within the range of 500–530 °C, and the time periods varied from 30 to 240 min under a static pressure of 5 MPa in a vacuum. The diffusion bonded specimens were subjected to T4- and T6-PWHT to improve the bonding quality. The interfacial microstructure of the joints was analyzed by scanning electron microscopy, and the mechanical properties were evaluated with shear tests. The experimental results showed that the shear strength of the diffusion bonded joint could reach around 71.2 MPa, which was highly dependent on bonding temperature and holding time, and T6-PWHT further enhanced it to over 100 MPa. The effects of PWHT on the diffusion bonded AA 6061 joint were investigated, and the fractography on the sheared surfaces indicated that PWHT-T6 played an important role in enhancing joint strength, which was consistent with the measured shear strength. The sequential PWHT for AA 6061 after diffusion bonding was proven to be feasible for bonding of AA 6061 parts, and the joint strength was sufficient for industrial needs.
Highlights
Aluminum alloys have been widely used in engineering structures in the automotive and aerospace industries due to their unique physical properties, such as low density, high specific strength, good formability, and excellent corrosion resistance
The present paper focuses on diffusion bonding of commercial AA6061, which is precipitation-strengthened by Al–Mg–Si intermetallic compounds (IMCs), and the joint is further strengthened by the post-weld heat treatment based on the temper grades of T4 and T6 [28], which were originally implemented for the purpose of strengthening the base material
This paper has presented the feasibility of solid-state diffusion bonding of alloy 6061 (AA 6061) joints and the effects of post-weld heat treatment (PWHT) on the mechanical properties and fracture mechanisms of the bonded AA 6061 specimens
Summary
Aluminum alloys have been widely used in engineering structures in the automotive and aerospace industries due to their unique physical properties, such as low density, high specific strength, good formability, and excellent corrosion resistance. To allow the utilization of aluminum alloys in these machinery manufacturing industries, the joining method is a major concern in the provision of complex structures for a wide variety of applications. Welding technologies such as laser beam welding (LBW) [1], tungsten inert gas welding (TIGW) [2,3,4], and friction stir welding (FSW) [5,6] have been adopted for a wide range of Al alloy joint structures.
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