T. Śleboda

The Range of the Occurrence of α Phase in near β Titanium Alloys

Two near β titanium alloys (Ti-3Al-8V-6Cr-4Mo-4Zr and Ti-10V-2Fe-3Al) were investigated in his research. Both materials contained disperse precipitations of α phase in β phase matrix. In the case of Ti-3Al-8V-6Cr-4Mo-4Zr alloy clear segregation of alloy constituents, resulting from casting process, were observed. This segregation caused different susceptibility to α phase precipitation in dendritic and interdendritic areas in the microstructure of the investigated alloy. The influence of the temperature, strain and processing time on α phase dissolution was determined. Gleeble compression tests were performed on both of the investigated alloys. The research showed different character of the influence of strain rate and processing time on the temperature of α phase dissolution for each alloy. The effect of heat treatment on α phase dissolution during ageing of the investigated alloys was also determined. The possibility of obtaining homogenous microstructure in these alloys by properly designed heat treatment was also discussed.

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.

Dynamic Recrystallization in Titanium Alloys

The results of the investigations on five different titanium alloys were presented in this paper. Two two-phase α+β alloys (Ti-6Al-4V and Ti-6Al-2Sn-4Zr-6Mo) as well as two β alloys (Ti-10V-2Fe-3Al and Ti-3Al-8V-6Cr-4Mo-4Zr) were studied. Moreover, Ti-48Al-2Cr-2Nb intermetallic alloy (γ alloy) was also investigated. All investigated alloys were tested in compression on Gleeble thermomechanical simulator under various strain rate and temperature conditions. Metallographic observations of the microstructure of tested samples allowed determining thermomechanical conditions under which dynamic recrystallization or recovery processes occurred in the investigated alloys. The obtained results also showed the importance of the influence of strong exothermic effect resulting from deformation process on recovery and recrystallization processes in these alloys. The methodology of distinguishing subgrains formed during recovery process from the grains resulting from recrystallization was also presented in this study.

Design and Verification of the Parameters of Hot Forging of Ti10V2Fe3Al Alloy Compacts

This research work was focused on the application of powder metallurgy technology to the production of high-quality products from Ti10V2Fe3Al alloy. For the purpose of investigations hot compaction and hot closed-die forging processes were used. As an initial material a mixture of elemental powders was applied. As a result of hot densification, fully densified semi-products were obtained (99.4 % relative density). Numerical modelling of forging of a selected forging was performed using finite element method. Various options of forging process conditions were applied. The designed parameters of forging technology were verified by means of trials performed in industrial conditions. The quality of the product was estimated by microstructure observations. It was found that hot forging of compacted mixture of elemental powders resulted in obtaining defect-free gear wheel showing the relative density of 99.8 ±0.2 %.