Scientists have come up with a way to delay the so-called “fatigue failure” in aluminum alloys
Aluminum metal is lightweight and has strong corrosion resistance, providing very desirable characteristics in automobile manufacturing. However, it may encounter problems due to its repeated alternating stress (for example, a paper clip bends back and forth until it breaks) and produces weak points. Scientists in Australia have proposed a solution to this so-called “fatigue failure”, which changes the microstructure of aluminum alloys so that they can repair these weak points by themselves.
Christopher Hutchinson, a professor at Monash University who led the research, said: “80% of engineering alloy failures are due to fatigue. Fatigue is failure due to alternating stresses. It is A very serious problem.”
Hutchinson and his team were the first to conduct this research, focusing on the underlying cause of fatigue known as the precipitation-free zone (PFZ). These weak links are formed in the aluminum alloy through alternating stresses, starting with tiny plastic points, and then forming cracks before the material finally breaks.
Hutchinson and his team of engineers tried early on to intervene in the process by using mechanical energy generated under alternating stress. More specifically, the team proposed a method to capture new particles and use these particles to reinforce weak points, stitch cracks together or delay the appearance of cracks.
This is achieved through a “training” process that simulates the strain imposed on the material (although it is higher than the normal stress) and needs to be repeated hundreds of cycles. This results in a higher concentration of fine particles in the weakened area, thereby increasing the yield strength and tensile strength of the material, which can then heal itself during operation.
Hutchinson said: “We have’trained’ the structure and used it to repair PFZ that may represent weak points. This method is universal and can be applied to other precipitation hardening alloys containing PFZs. And fatigue performance is an important consideration. .”
Researchers say that changing the initial microstructure in this way can significantly increase the fatigue life of aluminum alloys. They also pointed out that the fatigue strength of high-strength aluminum alloys is notoriously low, but they get the most benefits, mainly that the fatigue life can be extended by 25 times.
Hutchinson said: “Our research shows that the microstructure design of the aluminum alloy used for dynamic loading has undergone a conceptual change.”
“We did not design a strong microstructure, but wanted it to remain stable as long as possible during fatigue loads. We realized that the microstructure would change due to dynamic loads. Therefore, we designed an initial microstructure ( May have lower static strength), will change the way of work, thereby significantly improving its fatigue performance.
The research was published in the journal Nature Communications.
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