Researchers at the Lawrence Berkeley National Laboratory (LBNL) have made an extraordinary discovery: they have developed a metal alloy that remains stable at high temperatures and does not become brittle at extreme sub-zero temperatures - material properties that are actually incompatible.
The new alloy consists of niobium, tantalum, titanium and hafnium. It retains its strength even at temperatures of up to 1,600 °C and does not crack at temperatures as low as minus 196 °C. These properties make it a potential key component for engineering and aerospace applications where materials must withstand extreme conditions. The LBNL team led by David Cook discovered these properties during experiments with so-called refractory high entropy alloys (RHEA). These alloys consist of several metals with a high melting point, which are mixed in almost equal proportions.
Strength even at temperatures of up to 1,600 °C
"Our team has been working with such alloys for some time and we have repeatedly found that although these materials are very heat-stable, they have extremely low crack resistance," explains Cook's colleague Punit Kumar. However, the new alloy behaved differently and showed an unusual combination of hardness and flexibility. Analysis of the material structure using crystallographic methods revealed that special defects, known as kink bands, form in the alloy's crystal lattice. These bands suppress stress hardening and prevent the propagation of cracks by reorienting micro-stripes of the crystal towards the higher shear stress and directing damage away from the crack tip. This discovery could lead to the alloy being used in safety-critical applications such as reactors, engines or aerospace, as it exhibits exceptional crack stability across extreme temperature ranges.
However, until the alloy is used in practice, the research team plans to further investigate its characteristics and properties.
The results of the study were published in the journal "Science", doi: 10.1126/science.adn2428.
Sources: scinexx, DOE/Lawrence Berkeley National Laboratory
