Janusz Krawczyk

Development of microstructure and texture during recrystallization of a Cu-Al single crystal with (1 0 0)[0 1 1] orientation

Abstract Microstructure and texture development during recrystallization of a Cu−Al single crystal with (1xa00xa00)[0xa01xa01] orientation deformed by cold rolling to 80% reduction in thickness were investigated. The strongest components of recrystallization texture show the following relationships with the main component of the deformation texture: 30° 〈1xa01xa01〉 and about 45° 〈1xa01xa01〉. The orientations of the first nucleated grains do not show such relationships with the orientation of the deformed matrix.

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.

Microstructure and Tribological Properties of a Material with Cementite Eutectic Applied for Metallurgical Rolls

Three prototype metallurgical rolls were produced on the basis of G200CrNiMo4-3-3 material. The method applied for the microstructure forming was different for each roll: the roll marked WOT – as cast state (without a modification and heat treatment); the metallurgical roll marked WMT – during its casting the FeCaSi deoxidizing was applied and then modification by a complex inoculant and argoning; the metallurgical roll marked WNT – subjected to a heat treatment (incomplete normalizing).The mentioned above differences in the technology of making rolls caused changes in their microstructure.The cementite eutectic and pearlitic matrix occurred in each roll. The main differences in the microstructure of cast steel rolls concerned a morphology of precipitates of hypereutectoid cementite. In the WOT roll cementite was mainly in the Widmannstӓtten system. Precipitates of hypereutectoid cementite in the WMT roll occurred along grain boundaries of primary austenite. A large fraction of spheroidal hypereutectoid cementite, precipitated in the whole volume of the primary austenite grain, appeared in the WNT roll. The microstructure influenced the rolls hardness and was equal 260 ÷ 350 HBW.Tribological investigations indicated decreasing the abrasive wear resistance with increasing the hypereutectoid cementite fraction within the primary austenite grains.

Correlation of Tribological Properties of Titanium Alloys with their Microstructures

In general titanium alloys are associated with biomedical applications due to their unique properties such as: high biocompatibility, high strength to density ratio. They have been commonly used as a prosthetic material. However the microstructural development by heat treatment, directly correlated with the changes in mechanical properties of the material, allows us to consider these alloys as components of machines. One of the main properties of machine components are tribological properties. Knowledge of tribological properties of the machine elements allow us to determine the parts viability and improve the functionality of the entire engineering system. Titanium alloys are characterized by the low wear resistance caused by chemical reactivity and easy formation of adhesion joints. Intensive adhesive wear of this material is associated with the strong degradation of the material surface. To determine the influence of microstructure on the tribological properties of titanium alloys, dry sliding wear test was performed. The materials for the investigations were five titanium alloys. The tribological test was performed with a load of 100 N for 2000 s on a 500 m distance. The microstructural observations were performed by light microscopy, in addition the wear mechanism was also investigated and for each sample the mechanism of wear was defined. For this type of tribological test a small proportion of adhesive wear was observed. The main mechanisms of wear were microgridding and microcutting. The increase of material hardness does not seem to impact on the increase of average friction coefficient of the samples. Increase of friction coefficient corresponds to the decrease of mass loss for the titanium alloys.

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.