Quantitative Shape-Classification of Misfitting Precipitates during Cubic to Tetragonal Transformations: Phase-Field Simulations and Experiments.

The effectiveness of the mechanism of precipitation strengthening in metallic alloys depends on the shapes of the precipitates. Two different material systems are considered: tetragonal γ'' precipitates in Ni-based alloys and tetragonal θ' precipitates in Al-Cu-alloys. The shape formation and evolution of the tetragonally misfitting precipitates was investigated by means of experiments and phase-field simulations.

Simulation of the θ' Precipitation Process with Interfacial Anisotropy Effects in Al-Cu Alloys.

The effects of anisotropic interfacial properties and heterogeneous elasticity on the growth and ripening of plate-like θ'-phase (AlCu) in Al-1.69 at.% Cu alloy are studied.

Microstructure and Mechanical Properties of Precipitate Strengthened High Entropy Alloy AlCoCrFeNiTi with Additions of Hafnium and Molybdenum.

High entropy or compositionally complex alloys provide opportunities for optimization towards new high-temperature materials. Improvements in the equiatomic alloy AlCoCrCuFeNi (at.%) led to the base alloy for this work with the chemical composition AlCoCrFeNiTi (at.

Entropy Determination of Single-Phase High Entropy Alloys with Different Crystal Structures over a Wide Temperature Range.

We determined the entropy of high entropy alloys by investigating single-crystalline nickel and five high entropy alloys: two fcc-alloys, two bcc-alloys and one hcp-alloy. Since the configurational entropy of these single-phase alloys differs from alloys using a base element, it is important to quantify the entropy. Using differential scanning calorimetry, c-measurements are carried out from -170 °C to the materials' solidus temperatures T.

Tensile Behavior and Evolution of the Phases in the AlCoCrFeNiTi Compositionally Complex/High Entropy Alloy.

Compositionally complex alloys, or high entropy alloys, are good candidates for applications at higher temperatures in gas turbines. After their introduction, the equiatomic AlCoCrCuFeNi (at.%) served as a starting material and a long optimization road finally led to the recently optimized AlCoCrFeNiTi (at.

Laser Cladding of Ultra-Thin Nickel-Based Superalloy Sheets.

Laser cladding is a well-established process to apply coatings on metals. However, on substrates considerably thinner than 1 mm it is only rarely described in the literature. In this work 200 µm thin sheets of nickel-based superalloy 718 are coated with a powder of a cobalt-based alloy, Co-28Cr-9W-1.

Influence of W, Mo and Ti trace elements on the phase separation in Al8Co17Cr17Cu8Fe17Ni33 based high entropy alloy.

Compositionally complex alloys, also called high entropy alloys, have been investigated for over a decade in view of different applications, but so far only a small number of alloys can be considered as presenting good enough properties for industrial application. The most common family of elements is Al-Co-Cr-Cu-Fe-Ni. The equiatomic alloy having 5 phases and being too brittle, the composition has been modified in order to improve the mechanical properties.

An activated energy approach for accelerated testing of the deformation of UHMWPE in artificial joints.

The deformation behavior of ultrahigh molecular polyethylene (UHMWPE) is studied in the temperature range of 23-80 degrees C. Samples are examined in quasi-static compression, tensile and creep tests to determine the accelerated deformation of UHMWPE at elevated temperatures. The deformation mechanisms under compression load can be described by one strain rate and temperature dependent Eyring process.

Potential for adhesive wear in friction couples of UHMWPE running against oxidized zirconium, titanium nitride coatings, and cobalt-chromium alloys.

The classical wear mechanisms abrasion, fatigue, and adhesion are the most frequent causes of surface changes of ultra high molecular weight polyethylene (UHMWPE) in artificial joints. The counterpart material has a strong influence on the wear and friction behavior of artificial joints due to its abrasive properties and adhesive interaction with UHMWPE. The formation of a transfer layer on the counterpart in UHMWPE bearing systems is often described as being a clear indication of strong adhesive forces.

Abrasion resistance of oxidized zirconium in comparison with CoCrMo and titanium nitride coatings for artificial knee joints.

Most total knee replacement joints consist of a metal femoral component made from a cobalt-chromium- molybdenum (CoCrMo)-alloy and a tibial component with an ultrahigh molecular weight polyethylene (UHMWPE) bearing surface. Wear of the UHMWPE remains the primary disadvantage of these implants. The allergic potential ascribed to CoCrMo-alloys is a further concern.

Determination of the temperature rise within UHMWPE tibial components during tribological loading.

The wear of ultrahigh molecular weight polyethylene (UHMWPE) is considered as one of the major reasons for revision of artificial joints. While in vivo measurements have shown a significant temperature increase in knee implants, the amount of heat dissipated within the UHMWPE tibial component and its influence on the friction behavior when paired with a cobalt-chromium (CoCrMo) femoral component is unknown. Our goal was to address these questions by measuring the temperature rise over a wide range of tribological loading conditions that mimic certain spots on artificial knee joints.