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The influence of the hold time of the austempering heat treatment at 280°C on the microstructure and corrosion resistance in NaCl-based media of austempered ductile iron was investigated using X-ray diffraction, micro-hardness measurements, corrosion tests and surface observations. Martensite was only found in the sample which was heat treated for a short period (10 minutes). Corrosion tests revealed that this phase does not play any role in the anodic processes. Numerous small pits were observed in the a-phase which is the precursor sites in all samples (whatever the value of the hold time of the austempering heat treatment). [ABSTRACT FROM AUTHOR]

The article presents research aimed at determining the effect of adding rare earth elements to near-eutectic Al-Si and Al-Si- Ni alloys on the microstructure and mechanical properties of the obtained products. Material for the research was prepared using a melt spinner - a device used for rapid crystallization, casting thin ribbons, which were then subjected in subsequent stages to fragmentation, consolidation and plastic working. The ribbons and extruded rods cast were described in terms of their structure and their strength properties were determined at different measurement temperatures. It was shown that the lightweight materials produced from aluminium alloys using the rapid solidification process have an ultra-fine structure and good strength properties. Analysis under a microscope confirmed that the addition of rare earth alloys Al-Si and Al-Si-Ni causes fragmentation of the microstructure in the tapes produced. The presence of rare earth elements in the alloys tested has an impact on the type and the morphology of the particles of the microstructure's individual components. In addition to the change in particle morphology, the phenomenon of the separation of numerous nanometric particles of intermetallic phases containing rare earth elements was also observed. The change in microstructure caused by the addition of rare earth elements in the form of a mischmetal increases the mechanical properties. [ABSTRACT FROM AUTHOR]

The aim of this work is to develop a numerical model capable of predicting the grain density in the Mg-based matrix phase of an AZ91/SiC composite, as a function of the total mass fraction of the embedded SiC particles. Based on earlier work in a range of alloy systems, we assume an exponential relationship between the grain density and the maximum supercooling during solidification. Analysis of data from cast samples with different thicknesses, and mass fractions of added SiCp, permits conclusions to be drawn on the role of SiCp in increasing grain density. By fitting the data, an empirical nucleation law is derived that can be used in a micro model. Numerical simulation based on the model can predict the grain density of magnesium alloys containing SiC particles, using the mass fraction of the particles as inputs. These predictions are compared with measured data. [ABSTRACT FROM AUTHOR]

The main aim of this work was to numerically investigate and optimize feeding and geometrical parameters to produce inlet valves of Ti6Al4V alloy that are free from defects, especially porosity. It was found that the change of geometry orientation as well as inlet feeder diameter and angle showed distinct relationships between geometric alteration and occurrence of porosity. Alteration in the pouring parameters such as temperature and time had none or only slight effect on occurrence or position of porosity in the valve. It was also found that investigating individual parameters of simple geometry and then utilizing these best fit results in complex geometry yielded beneficial results that would otherwise not be attainable. [ABSTRACT FROM AUTHOR]

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