Materials scientists in China have turned a common flaw in metal alloys into a component that increases their strength. Experts have created pure gold with nano-sized holes evenly distributed throughout the metal. The new method makes the material lighter, stronger and more plastic, which could expand the possibilities for using this type of gold.

There are many ways to strengthen metal. Different components can be mixed to create a heat-resistant, corrosion-resistant or magnetic alloy. There are chemical processing methods that strengthen metal, such as nitriding. Various hardening technologies, etc., have been known for a long time.

The demand for lightweight and strong metals is increasing in the industry due to manufacturers’ efforts to be energy efficient and environmentally friendly. It is possible to reduce the weight of parts by using lighter metals such as aluminum in the composition, but materials scientists are looking for opportunities to do the opposite, that is, to create hollow workpieces without losing them. However, a problem arises here because hollows are a defect that causes cracks and often makes the metal brittle.

In the magazine the other day Science A group of researchers from China published an article in which they talked about a new method of strengthening gold with the help of holes. Experts prepared pure gold with nanovoids evenly distributed in it – they were formed after the removal of silver residues from the alloy by corrosion.

The size of this period was about 30 nanometers, and so that it would not weaken the metal, scientists compressed and heated the studied samples at a temperature of 424.85 ° C. In order for the porous structure to close, it was necessary to press the metal to a critical density. After the process, most of the voids turned into spheres with a minimum diameter of 18 nanometers.

To test how the mechanical properties of gold change, materials scientists took small samples with holes of various sizes (18-180 nanometers in diameter) and stretched them. It turned out that the strength of the holey gold increased when the averaging time was shortened, but all samples outperformed the untreated gold. The porous metal had almost 107% higher yield strength, and the added 5% voids increased the strength-to-weight ratio by 118%.

As the researchers noted, some samples with particularly large pores showed increased strength as well as increased flexibility. The main difference between the new technology and conventional porous metals is that the pores in the studied substrate are evenly distributed, which minimizes stress concentration in one place. In order to strengthen the metal better, the pores need to be reduced, because with them the areas with high stress during loading are also reduced. The limit is around 101-102 nanometers; at this diameter the strength increases without loss of plasticity.

The new approach could be more scientifically called a zero-mass component. The holes could make the metal 10% lighter, improving its physical properties. The holey gold could be used to machine contacts in electronics, but the researchers plan to test the method with copper, the gold most commonly used in such devices.