Engineers at Monash University in Australia have developed a high-strength aluminum alloy with a 25-fold increase in fatigue life. For the transportation manufacturing industry, this invention is of great significance.
The researchers said that the reason for the poor fatigue performance of high-strength aluminum alloys is a weak link called the "precipitation-free zone" (PFZ). A team led by Professor Christopher Hutchinson from the Department of Materials Engineering at Monash University has developed an aluminum alloy microstructure that can repair weak links during operation (a form of self-repair). Compared with the most advanced alloys, the life of high-strength aluminum alloys can be increased by 25 times.
Aluminum alloy is currently the second most popular engineering alloy. Compared with steel, they are light weight (one-third density), non-magnetic, and have excellent corrosion resistance. In transportation applications, aluminum alloys occupy an important position because they are light and can improve fuel efficiency. However, compared with steel of similar strength, its fatigue properties are very poor. Professor Hutchinson said: "80% of engineering alloy failures are caused by fatigue. Fatigue failure due to alternating stress is a big problem in manufacturing and engineering."
Material fatigue failure occurs in stages. In the weak link of the material, alternating stress will lead to micro-plasticization of the material (due to permanent changes in stress) and accumulated damage in the form of local plasticization. Local plasticization will induce fatigue cracks, which gradually expand and eventually lead to material fracture. Researchers use commercial AA2024, AA6061 and AA7050 aluminum alloys to repair weak links in the PFZ microstructure through the mechanical energy applied to the material in the early fatigue cycle, thereby greatly delaying local plasticization, avoiding fatigue cracks, and improving fatigue life And intensity.
Professor Hutchinson said that as the demand for fuel-efficient, light-weight and durable aircraft, cars, trucks and trains continues to grow, these findings have important implications for the transportation manufacturing industry. Studies have shown that in the application of dynamic loads, the microstructure design of aluminum alloy has undergone a conceptual change. He said: "We are not designing a robust microstructure and want it to remain stable for as long as possible during fatigue loads. We recognize that dynamic loads will change the microstructure. Therefore, we designed an initial microstructure, although The static strength may be lower, but it will change and significantly improve fatigue performance."
"In a sense, this is to train the structure and use a training plan to repair the weak points of PFZ. This method is universal and can be applied to other precipitation hardening alloys containing PFZ. For these alloys , Fatigue performance is an important consideration."