SUPERHYDROPHOBIC COPPER SURFACES BY SHOT PEENING AND CHEMICAL TREATMENT

In this paper, superhydrophobic surfaces are developed on polycrystalline copper using a combination of mechanical and chemical treatments by shot peening, dislocation etching and stearic acid treatment. The key point in this combined approach is the fabrication of a dislocation forest by shot peening. These sites were dissolved by etching, and hierarchical structures were fabricated. When these etched surfaces are treated by stearic acid, which has low surface energy, they become superhydrophobic with contact angle more than 150[Formula: see text]. Because of the superior properties and low costs involved with this method, it is expected to be widely used in the industry to fabricate superhydrophobic surfaces.

Modelling Yield Strength in an A6061 Aluminium Alloy

The yield strength of an A6061 Aluminium alloy for different artificial ageing times, strain rates and temperatures is modelled taking into account precipitation, solid solution and dislocation forest strengthening. Precipitation kinetics during artificial aging and the individual strength contributions are simulated with the thermokinetic software package MatCalc. In the present contribution, we introduce the model for the temperature and strain rate dependence of the yield-strength based on thermal activation theory. The experimental work presented here is performed on a Gleeble 1500 thermo-mechanical simulator, where the solution annealed and quenched samples are heat treated to produce materials in various microstructural conditions. We demonstrate that yield strength simulation is a powerful tool to reduce experimental effort and to cut down costs in the process of alloy engineering. This approach consistently represents the yielding behaviour of alloys in a variety of microstructural conditions with respect to the production history of the alloy and the testing conditions, i.e. temperature and strain rate.

Dislocation Forest Interactions: Simulation and Prediction

Using linear elastic dislocation dynamics simulations, we show that junction formation between dislocations from various interacting slip systems can be predicted by a simple self-energy calculation. We find that this prediction is robust: dislocation curvature and external stress produce little change in the simulation results for junction formation. One key to this success appears to be a separation of timescales, where movement of the far away dislocation arms (under, for example, external stress) is typically slow compared to the process of making a junction. The self-energy calculation we describe gives a rule for dislocation encounters which should allow a considerable saving in computational effort, allowing one to impose correct interaction outcomes without calculating the interactions in detail. We also find that dislocations often come together under attraction without forming a junction. The resulting “cross-linked” state provides an additional type of connection between dislocations. We include preliminary results on the persistence of junctions and cross-linked states under stress.