Effect of Stabilization on microstructures, mechanical properties and corrosion resistance of Al-7Mg forged alloys

Project Details

Description

The 500-series Al-Mg alloys are non-heat-treatable casting alloys. Generally, used after homogenization, and been widely used in ship chairs because of its good machinability, excellent corrosion resistance and surface finishing, etc. While the Mg content is >3wt.%, alloy in the range of 50~90°C for a long time, Mg and Al tend to precipitate β-Mg2Al3 at the grain boundary. If the β phase precipitates in a continuous network on the grain boundary. The sensitization phenomenon of the intergranular corrosion of the alloy in a corrosive environment results in a significant attenuation of the original excellent corrosion resistance. B535.0(Al-7Mg-0.15Ti) is a cast aluminum-magnesium alloy containing high magnesium. It has good corrosion resistance and weldability. Its T5 strength and ductility can reach 260MPa and 10% respectively, and it has been widely used in ship structures and aviation materials under corrosive environment. The magnesium content of B535.0 alloy is as high as 7wt%, this alloy has extremely high solid solution strengthening and working strengthening, and slightly dispersion strengthening effect, so often regarded as poor formability, not easy to use as forgings. However, tests by a partner company (JinQuanxing) found that this alloy has excellent hot and cold workability, and can be successfully made into forged wires and plates (temporarily named MB5350 alloy). However, whether this alloy (MB5350 alloy) has good corrosion resistance is the key to whether this forged material has practical value. Since aluminum-magnesium alloys are often used at the sensitization temperature (50~90℃), sensitization is an inevitable process, which causes the aluminum-magnesium casting alloy to have a problem of being sensitive to corrosion. The cooperative enterprise is limited to its own research and development capabilities. This topic cannot be effectively researched and developed to solve practical problems and principles. Therefore, this case is requested to improve the accuracy of practical applications and provide a theoretical reference for the theory. The leading of this study found that MB5350 forged alloy, after being stabilized at (250~300℃), was tested by ASTM-G67, its nitric acid corrosion weight loss test value was less than 18mg/cm2, only slightly higher than 15mg/cm2 without intergranular corrosion sensitivity. (But not serious) But it is rare that its (T5 state) mechanical strength can reach 325MPa, and the ductility also reaches 12%, which is better than B535.0 alloy. The cooperating enterprise deeply felt that there was a practical opportunity for this result, and the applicant also felt that the use of heat treatment theory could overcome the problem of slightly higher sensitivity to intergranular corrosion. In addition, it was also necessary to discuss its theory clearly, so this project was proposed.
StatusFinished
Effective start/end date1/11/2031/10/21

UN Sustainable Development Goals

In 2015, UN member states agreed to 17 global Sustainable Development Goals (SDGs) to end poverty, protect the planet and ensure prosperity for all. This project contributes towards the following SDG(s):

  • SDG 9 - Industry, Innovation, and Infrastructure
  • SDG 12 - Responsible Consumption and Production
  • SDG 17 - Partnerships for the Goals

Keywords

  • stabilization treatment
  • forged Al-Mg alloy
  • intergranular corrosion
  • β-phase(Mg2Al3)
  • sensitization

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