G. Cios

The Influence of Cooling Rate During Crystallization on the Effective Partitioning Coefficient in High-Entropy Alloys from Al-Ti-Co-Ni-Fe System

An influence of two different cooling rates on the microstructure and dispersion of the components of high-entropy alloy from Al-Ti-Co-Ni-Fe system has been examined. For investigated alloys, the effective partitioning coefficient has been calculated. This factor indicates the degree of segregation of elements and allows for the specification of the differences between dendrites and interdendritic regions. The obtained results allow for the conclusion that the cooling rate substantially affect the growth of dendrites and the volume fraction of interdendritic regions as well as the partitioning of elements in the alloy. Furthermore, the obtained results made it possible to compare the influence of the cooling rate and the chemical composition on the dispersion of the alloying elements.

Strain-induced martensite reversion in 18Cr–8Ni steel – transmission Kikuchi diffraction study

ABSTRACT Reverse transformation of strain-induced martensite (SIM) was studied in the 18Cr–8Ni stainless steel. Microstructure analysis was performed on samples in an as-deformed state and after reversion annealing at 873 and 973 K, using the transmission Kikuchi diffraction. The primary, as well as reversed, austenite possesses the Kurdjumov–Sachs crystallographic orientation relationship, with respect to the SIM. The reverted austenite keeps one orientation within all reverted grains, regardless of the applied heating procedure, where the amount of reverted austenite depends only on the annealing temperature.

T-Shape Connector Hydroforming Process Analysis

The work is focused on hydroforming of T-shape connector for high temperature applications. A seamless part for use in industrial applications was formed in a high pressure liquid extrusion process. Due to the occurrence of faults in the final products, numerical simulations were conducted to reveal the possible sources of such failures. The numerical simulation took into account precisely determined boundary conditions allowing proper selection of processing parameters. The microstructure of charge material as well as that of the final product was also examined. Numerical simulations of the investigated extrusion process showed the possibility of obtaining good quality product, however, the quality of final part is strongly influenced by properly designed heat treatment schedule.