Brad Boyce, a materials scientist at Sandia National Laboratories, and his colleagues at Texas A&M University have witnessed an amazing phenomenon: pieces of metal cracking and then fusing back together without human intervention. This discovery could lead to an engineering revolution where self-healing bridges, engines and airplanes can repair damage caused by wear and tear and become safer and more durable.
Fatigue damage is one of the main causes of wear and breakdown of machines. Repetitive loads or movements over time cause microscopic cracks to appear and grow, which eventually lead to complete failure of the device. Researchers have discovered that tiny cracks at the nanoscale can disappear and heal on their own.
“From the solder joints in our electronic devices to the engines of our cars and the bridges we drive over, these structures often fail unpredictably due to cyclic loading that leads to cracks and eventual failure,” Boyce explains. The economic impact of such failures is estimated at hundreds of billions of dollars annually for the U.S.
Previously, self-healing materials have been created by scientists, but they were mostly plastics. Self-repairing metal was thought to be impossible. However, in 2013, Michael Demkovich, a professor at Texas A&M University, proposed a theory that metals can self-heal under certain conditions.
Now scientists at Sandia National Laboratories have confirmed this hypothesis. They have investigated how cracks form and propagate in a nanoscale piece of platinum using a special electron microscope technique. It turned out that after repeatedly pulling and stretching the metal, the crack in one place suddenly changed direction and one end of the crack fused together as if retracing its steps, leaving no trace of the previous damage. The crack then began to grow in a different direction.
This discovery opens up new possibilities in engineering. Self-repairing metal could be used to create stronger and more durable structures that can repair damage caused by wear and tear. This will reduce replacement and repair costs, and increase the safety and reliability of machines and structures.
“We are just beginning to realize the potential of self-healing metal,” says Boyce. “This discovery could lead to new technologies and innovations that will change our lives.”