Aneta Łukaszek-Sołek

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.

The role of the deformation conditions in the evolution of the microstructure of the Ti-6Al-2Sn-4Zr-6Mo alloy

This work discusses the influence of the processing temperature, time and processing strain on the microstructure of the Ti6Al2Sn4Zr6Mo alloy. The Ti6Al2Sn4Zr6Mo alloy belongs to the two-phase (α+β) type of titanium alloys. The samples were compressed with the use of the Gleeble thermo-mechanical simulator at the temperatures of: 800, 900, 950, 1000 and 1100°C and at the strain rates of: 0.01; 0.1; 1; 10 and 100 s-1 to a total true strain of 1. The occurrence of the primary α phase in the Ti6Al2Sn4Zr6Mo alloy was investigated. The diagram showing the influence of the processing temperature and the strain rate on the dynamic recrystallization of the β phase was presented.The occurrence of the primary α phase precipitates blocks the grain growth. Therefore, the plastic deformation of this alloy should be carried out at a temperature at which the separation of the primary α phase occurs to finally obtain a material with a fine grain.

Processing Maps of the Ti-6Al-4V Alloy in a Forging Process Design

The paper presents the results of a complex study of the Ti-6Al-4V alloy, conducted with the application of the dynamic material modelling (DMM) method, in a wide range of temperatures, strain rates and strains. A compression test was carried out in a wide range of temperatures (800 – 1100°C) and strain rates (0.01 – 100 s-1), up to the constant final true strain value of 0.9. The obtained stress-strain curves were a basis for determining deformation activation energy with the use of an Arrhenius plot and a correlation between the Zener-Hollomon parameter and flow stress, for which the constitutive equation proposed by Sellars was used. The power dissipation efficiency parameter was calculated. The maps of power dissipation as the function of temperature and strain rate were plotted in the form of the isoclines of the power dissipation efficiency parameter expressed in %. The processing maps exhibited the range of occurrence and recrystallization of the primary α phase, the degree of the β phase recrystallization progress against the background of the process deformation windows and instability flow domain. An analysis of the influence of process parameters up on the microstructure and hardness changes was conducted.

The Hammer Forging of Ti-6Al-4V Alloy

In this paper, the research results of hammer forging process of titanium alloy Ti-6Al-4V are described. It is hard deformable alloy so forming details with complex shape from this alloy requires precise selection of thermomechanical parameters. Proper design of technological forging process of forging from Ti-6Al-4V alloy, taking into account the initial metal working, shape of supportive impressions, lubricants with proper tribological properties and also proper selected temperatures of tools and material allows to get the final product without defects. The numerical modelling based on the FE software QForm 3D was carried out. The distributions of temperature, effective strain and material flow kinematics were analyzed. The correctness of the modelling results was verified by the forging test performed in industrial conditions. Hammer forging tests were made in Polish forging plants. The products of good quality were obtained.

Textures of the Hot-Forged Ti6Al4V Alloy

This paper presents the results of the texture investigation in the hexagonal phase and the body-centered cubic  phase of the Ti6Al4V alloy hot-deformed by forging. Forging was performed at two different temperatures on the occurrence of the single  and in the two-phase  +  state. It was found that after deformation both  and  phases are textured and their textures strongly depends on deformation temperature.