Twin dilemma for strong but ductile metals

A combination of electron microscopy and computer modelling has helped materials scientists discover a quirk of behaviour in nanoscale samples of tungsten that could help discover ways to improve material strength without sacrificing its ability to be processed into different shapes. Key to the discovery was a new technique to make samples of nanowires small enough to be studied by high-resolution transmission electron microscopy.

The researchers, from Georgia Tech in Atlanta, the University of Pittsburgh and Drexel University in Philadelphia, first had to devise a way to make tungsten samples below 100nm in size. Graduate student Jiang Wang and research leader Scott Mao, both of Pittsburgh’s Swanson School of Engineering, welded together two small pieces of individual tungsten crystals to create a 20nm nanowire, which allowed the arrangement of atoms in the crystal, a form known as a body-centred cube (BCC), to be resolved by the microscopes. BCC structures are based on a unit of eight atoms at the vertices of a cube surrounding a single atom in the middle.