In situ correlation between metastable phase-transformation mechanism and kinetics in a metallic glass.

A combination of complementary high-energy X-ray diffraction, containerless solidification during electromagnetic levitation and transmission electron microscopy is used to map in situ the phase evolution in a prototype Cu-Zr-Al glass during flash-annealing imposed at a rate ranging from 10 to 10 K s and during cooling from the liquid state. Such a combination of experimental techniques provides hitherto inaccessible insight into the phase-transformation mechanism and its kinetics with high temporal resolution over the entire temperature range of the existence of the supercooled liquid. On flash-annealing, most of the formed phases represent transient (metastable) states - they crystallographically conform to their equilibrium phases but the compositions, revealed by atom probe tomography, are different.

On the Formation Mechanism of Column Damage Within Modular Taper Junctions.

Background: Column damage is a unique degradation pattern observed in cobalt-chromium-molybdenum (CoCrMo) femoral head taper surfaces that resemble column-like troughs in the proximal-distal direction. We investigate the metallurgical origin of this phenomenon.

Methods: Thirty-two severely damaged CoCrMo femoral head retrievals from 7 different manufacturers were investigated for the presence of column damage and chemical inhomogeneities within the alloy microstructure via metallographic evaluation of samples sectioned off from the femoral heads.

Nanoglass-Nanocrystal Composite-a Novel Material Class for Enhanced Strength-Plasticity Synergy.

The properties of a material can be engineered by manipulating its atomic and chemical architecture. Nanoglasses which have been recently invented and comprise nanosized glassy particles separated by amorphous interfaces, have shown promising properties. A potential way to exploit the structural benefits of nanoglasses and of nanocrystalline materials is to optimize the composition to obtain crystals forming within the glassy particles.

Crystal-Glass High-Entropy Nanocomposites with Near Theoretical Compressive Strength and Large Deformability.

High-entropy alloys (HEAs) and metallic glasses (MGs) are two material classes based on the massive mixing of multiple-principal elements. HEAs are single or multiphase crystalline solid solutions with high ductility. MGs with amorphous structure have superior strength but usually poor ductility.

Atomic Scale Origin of Metal Ion Release from Hip Implant Taper Junctions.

Millions worldwide suffer from arthritis of the hips, and total hip replacement is a clinically successful treatment for end-stage arthritis patients. Typical hip implants incorporate a cobalt alloy (Co-Cr-Mo) femoral head fixed on a titanium alloy (Ti-6Al-4V) femoral stem via a Morse taper junction. However, fretting and corrosion at this junction can cause release of wear particles and metal ions from the metallic implant, leading to local and systemic toxicity in patients.