New research shows nanovoids improve material performance.
Could porosity be a good thing in metal additive manufacturing?
Voids or pores are typically viewed as fatal flaws that severely degrade a material’s mechanical performance and, for this reason, they’re generally avoided in additive manufacturing.
However, a research team led by Prof. JIN Haijun from the Institute of Metal Research at the Chinese Academy of Sciences has proposed that the presence of voids is not always hazardous. Instead, voids can be beneficial if they are added “properly” to the material.
The team demonstrated that a metal with a large number of nanoscale voids shows improved mechanical performance compared to samples without voids.
The new material developed by the team has been dubbed nanovoid dispersed gold (NVD Au). It contains a huge number of nanoscale voids, with sizes ranging from a few nanometers to several hundred nanometers, distributed uniformly throughout the material. Manufacturing NVD Au combines a process of dealloying with compression and thermal annealing treatments.
The researchers found that NVD Au shows improved strength and ductility in tension in comparison with fully dense Au.
This is the exact opposite of the effect observed in materials with large voids that are prepared by powder sintering and other metal 3D printing techniques. The researchers attribute the enhanced properties of NVD Au to improved dislocation-surface interactions and suppressed crack nucleation in this structure.
“We achieved both NVD strengthening and density reduction simultaneously, and thus realized lightweighting,” said JIN in a press release. “Also, it does not involve any change of composition or phase, so that the excellent physical/chemical properties of the base material can be largely preserved.”
The team believes their strengthening approach could have applications in many areas, ranging from portable electronics to aviation manufacturing.
The study was conducted in collaboration with scientists from Liaoning Academy of Materials and Nanjing University of Science and Technology.
The research is published in Science.
