Degradable silver-based alloys

Noble metals solved in iron implants are effective cathodes, which can suit to accelerate the corrosion rate of the base material. In terms of its antibacterial behavior as well as lower costs in comparison with gold or platinum, silver seems to be an attractive candidate to adapt the corrosion rate of implants to the medical requirements. However, the degradation of silver in human bodies is a time-consuming process, and is controversially discussed due to the unknown long-term effect of silver on the human organism. Alloying silver with chemical elements less resistant to corrosion in aqueous mediums, particularly, in simulated body fluid, can improve the degradability of silver. Therefore, the current study addresses the design of adapted silver alloys exhibiting improved degradability in comparison with pure silver. Pure silver and binary silver alloys containing silicon, magnesium and calcium are studied in terms of their microstructure, open-circuit potential and degradation rate.     

Optical Detection of Phase Transformations in Steels: An Innovative Method for Time-Efficient Material Characterization During Tailored Thermo-mechanical Processing of a Press Hardening Steel

Metallurgical and Materials Transactions A - With an innovative optical characterization method, using high-temperature digital image correlation in combination with thermal imaging, the local...     

Spray cooling of extruded EN AW-6082 aluminium alloy sheets: spatial heat transfer coefficients

Quenching profiles during their extrusion with subsequent ageing can increase their strength by a factor of 1.5–2 compared to the as-extruded state. Water-air spray cooling is a quenching technology which allows the desired profile temperature to be reached with high accuracy and which is characterised by low energy demand. To apply this cooling technique correctly, the heat transfer coefficient’s dependence on the surface temperature and properties of the extruded profile, made from EN AW-6082 alloy, and on the spray cooling parameters was determined using the lumped heat capacitance method. The absence of a significant impact of the spraying distance and inclination angle on the average heat transfer coefficient within the investigated range was noted. Dependencies of the relative heat transfer coefficient on the temperature and the distance to the spray axis were derived. It was shown that these dependencies, which can be used for modelling such processes, are practically identical for all considered spraying parameters.     

Assessment of subcritical crack growth in hydrogen-containing environment by the parameters of acoustic emission signals

Estimation models (differential equations, initial and final conditions) for determining the crack propagation kinetics in hydrogen-containing environments using the acoustic emission (AE) signal parameters are proposed. The formulation of these models is based on the main ideals of the AE method, dependence between the crack increment area and a sum of AE-signals amplitude, main criteria of fracture mechanics and laws of thermodynamics.     

Microstructure Transformations in Tempering Steels during Continuous Cooling from Hot Forging Temperatures

Apart from reducing the processing energy, hardening and tempering of near‐net shape forged components from their forging heat primarily promises shortened conventional process sequences. In this case, the continuous cooling transformation diagrams (CCT diagrams) found in the literature can only be used as a rough approximation of microstructural transformations during the heat‐treatment. The reasons for this are that firstly, the deformation influences the transformation kinetics and secondly, the deformation temperatures are comparatively high. Therefore, both deformation CCT diagrams and, for reference purposes, CCT diagrams without deformation were determined for a selection of heat‐treatable steels (34CrMo4, 42CrMo4, 52CrMo4, 51CrV4, 34NiMo6) at the heating temperature of 1200 °C and deformation levels of 0.3 and 0.6.