Top Result for FY2021

Revealing the strengthening mechanism of metallic materials by nanoscale defects

Masato Wakeda
Principal Researcher, Mechanical Properties Group, Materials Evaluation Field, Research Center for Structural Materials

Although defects such as cracks induce fractures, many nanoscale defects can actually increase the strength of metallic materials. This may sound surprising, but metallic materials strengthened by nanoscale defects are widely used in our society. To develop metallic materials with more strength, it is useful to understand the relationship between nanoscale defects and strength. There are various types of defects in metallic materials, and many phenomena related to strength occur at the nanoscale. This study combines nanoscale mechanical testing, observation, and atomistic simulation to reveal the relationship between the types of grain boundaries (planar defects) and their contribution to strength, and the origin of this relationship.

Q＆A

Q：How can "defects," which seem bad, improve the strength of a material?
A：Deformation of metallic materials is often induced by the motion of very small, but large in number, line defects. When the movement of the line defect is disturbed by other defects, the metallic material becomes less deformable. This is how defects make metallic materials stronger.

Q：Are defects visible?
A：Defects such as large cracks can be visible, but the small defects that make a metal stronger are basically invisible. There are many types of defects, the smallest of which are on the atomic scale. Some defects can be observed by using special experimental equipment.

Q：What is the point of this achievement?
A：The key is that we have investigated the origin of the strength of metals by combining experimental equipment that allows us to reveal the strength of materials in the nanoscale region, observation equipment that allows us to see the region, and atomic-scale simulations. These methods can complement each other and give us new information about the origin of strengthening mechanisms related to the grain boundary.

Q：When do you get excited in your research activities?
A：When I get new results that I did not expect, or when I come up with a new idea, I get excited. Although the ideas I come up with are often infeasible, I enjoy thinking about them. I also enjoy it when I apply new simulation approaches to materials.