Metallic glass (amorphous metal) is a sturdy material that is finding its way into a number of applications, including nanomolds, as a biomaterial for setting broken bones, and for use in cell phones and other devices. Sometimes, however, the material can crack or break. Researchers at Johns Hopkins University have been studying this phenomena using computer simulations to determine how much energy is required to crack the material, and how susceptible it is to breakage.
A process called cavitation causes the formation of tiny bubbles in the glass under high negative pressure, and can play a role in these failures. Using a computer model of a cube of metallic glass, the researchers looked at the conditions under which the bubbles form.
According to a press release from the university:
The simulations revealed that these bubbles emerge in a way that is well predicted by classical theories, but that the bubble formation also competes with attempts by the glass to reshuffle its atoms to release the stress applied to a particular location. That second process is known as a shear transformation. As the glass responds to pressure, which of the two processes has the upper hand—bubble formation or shear transformation—varies, the researchers found. For example, they determined that bubbles dominate in the presence of high tensile loads, meaning the strong pulling forces that are more common near the tip of a crack. But when the pulling forces were at a low level, the atom reshuffling process prevailed.
“Our aim is to incorporate our findings into predictive models of failure for these materials,” said Michael Falk, professor in the Whiting School of Engineering’s Department of Materials Science and Engineering, “so that they can be optimized and used in applications that require materials that are both strong and fracture-resistant.”
You can read more about the research in the journal Physical Review Letters.
Source: Johns Hopkins