The latest development of rheocasting process is based on the principles of HPDC. The material in semi-solid state is pressed into the tool cavity. That enables faster solidification and better productivity. Due the narrow temperature window the optimization of the new rheocasting process demands precise control of process parameters. Presented is development of the microstructure of the semi-solid slurry and the rheocast Component, an overview of observed defects in components produced by new rheocating process as well as results of simulation of the HPDC of Al-Si9Cu3 casting in the H13 steel die. A comparison between the simulated porosity and experimental determined porosity is presented.
COBISS.SI-ID: 1200991
Results show that each production phase has a considerable influence on residual stress field generated in double-layer cast rolls. Surfaces exposed to too high cooling rates in the casting pit general show higher residual stress values. Very critical phase in the rolls production is coarse grinding, which if not carried out properly generates very high tensile stresses and cracks. Heat treatment on the other hand results in uniform compressive residual stress field. Finally, machining parameters needs to be carefully selected not to introduce too much residual stresses in the rolls surface.
COBISS.SI-ID: 11388699
Equilibrium solidification thermal effects can also be represented with the calculated heat capacity using the complete or partial chemical compositions of complex alloy systems based on Fe-Cr-Ni. The use of Creq and Nieq in the solidification studies should be used after critical assessment
COBISS.SI-ID: 1259615
Vacuum heat treatment, deep cryogenic treatment and pulse plasma nitriding are efficient techniques to improve the properties of tool and high speed steels. Sometimes the influence of subzero treatment could be directly ascribed to the transformation of retained austenite into martensite, causing a general increase in hardness. In other cases the increase in wear resistance is not supported by higher hardness and several theories with poor experimental evidence were proposed. In this work specific attention was paid to the influence of subzero treatment just after quenching and solubilization in the vacuum heat treatment or simultaneous pulse plasma nitriding and tempering of high speed steel. Special emphasis was put on resistance to galling and abrasive wear resistance under dry sliding conditions. From obtained results it can be concluded, that the application of deep-cryogenic treatment results in a significantly higher wear resistance of high speed steels, but no significant improvements in fracture toughness have been noticed
COBISS.SI-ID: 890794
Tachnological development causes the more often presence of nano fibers in our environment. For that reason there is a question of the influence of nano fibers on living organisms and how to control this influence. Usual method, applied in biology is thin slicing of tissue and the control with light microscope. Such process is time consuming and expensive. The proposed method enables to control the surface of digestive system with scanning electron microscope (SEM). The comparison of non contaminated surface with nano fibers contaminated surface is eassy Method with SEM revealed that most of nano fibers pass the digestive system. Some shorter nano fibers, with the length similar to distance between epithelial cells, can pierce the epithelial cell wall during contraction period of digestive tube and broke during next contractions.
COBISS.SI-ID: 946346