Abstract: In the present paper the wettability of a liquid metal by another liquid metal is studied theoretically,
based on a recent model on interfacial energies in metallic systems. It appears that in all practical
cases the liquid metal with a lower surface tension will perfectly wet (with a zero contact angle) the
liquid metal with a higher surface tension practically at any temperature, and therefore will
encapsulate it. As a result, the first order surface phase transition will start in monotectic metallic
systems at 0 K. The phenomenon of the surface phase transition is considered in some details, based
on a recent paper.
Abstract: The process known as Tempcore is used to produce high resistance rods by the formation
of a surface layer of quenched and tempered martensite that surrounds a core made of ferrite and
pearlite. Such a mixed structure is result of processing hot rolled rods through waters headers that
reduce the temperature at the surface below that for the transformation into martensite. This
structure is tempered by the heat flowing from the core of the rod, which transforms into ferrite and
pearlite while the rod is in the cooling beds. Such processing produces a significant increase in yield
and ultimate tensile strength, while maintaining adequate ductility. The economic advantages of this
process are huge in comparison with those that require alloying elements or further metal working
to improve mechanical properties. A series of experimental trials were carried out in a pilot plant in
which parameters such as reheating temperature, water flow and processing time were varied to
study their effect on the mechanical properties of carbon steel rods and on the structures formed in
the bars. The study is being complemented by the thermal modelling by the finite element method.
Abstract: The author developed a three-dimensional model for the description of fast plastic
deformation of metals in the case of cutting. Shear strain occurring as a result of shear stress
has a reverse effect on stress, while the temperature of the material is increasing. These
counteracting effects may lead to thermomechanic instability, which may result in aperiodic
chaotic conditions besides periodic fluctuation due to the non-linear nature of the process.
Apart from bifurcation and multi-cycle periodic deformation, the model also describes
aperiodic chaotic deformation, which is proven by experimental results.
Abstract: The final microstructure of DP and TRIP assisted steels can evolve after hot working
(hot rolling) or during post heat treatment process. In the formation of the final structure a number
of different technological parameters have important role, e.g. finishing temperature of rolling,
cooling rates, temperature of intercritical annealing, etc. As a result of the individual factors and
their combinations a lot of production technology routes are feasible. The effect of the different
combinations of these technological parameters on the microstructure can be mapped by a special
Jominy end-quench test (so called intercritical Jominy end-quench test) described in this paper.
Unlike the traditional Jominy test, in this case there is a partial austenizing between A1 and A3
temperatures which results in a given amount of ferrite in the microstructure before quenching. The
amount of ferrite depends on the temperature. In some cases the quenching process was interrupted
for a given period of time in order to model the cooling process on the run-out table. During cooling
each point of the Jominy specimen has a different cooling rate, so the effect of cooling rate on the
microstructure can be evaluated along the length of the specimen.
Abstract: This paper deals with the characterization of solidification, cooling and expected
properties of continuously cast slabs. Semi-empirical models based on theoretical consideration and
on the results of heat transfer model are used for characterization of the following: surface and inner
temperature distribution of the cast semis, liquid sump depth and shape, liquid motion intensity
resulting in centerline segregation, parameters of the primary dendritic structure (primary and
secondary dendritic spacings, columnar to equiaxed transition position, CET). This method
provides an opportunity to make a realistic comparison between the solidification and final
properties of semis with different chemical compositions as a function of applied casting
technologies. The final goal of this research activity in the future is to define a comprehensive
quality function for optimizing continuous casting technology.
Abstract: To characterize topologically the polycrystalline microstructure of single-phase alloys
computer simulations are performed on 3-dimensional cellular models. These infinite periodic
cellular systems are constructed from a finite set of space filling convex polyhedra (grains). It is
shown that the appropriately selected topological shape factors can be successfully used for the
quantitative characterization of computer-simulated microstructures of various types.
Abstract: Kinetic models of new types are suggested which are designated primarily to predict the
progress of non-isothermal transformations occurring during rapid heating and cooling in alloys. A
common feature of each model outlined is that it takes into account not only the varying
temperature but also the rate of temperature change on the transformation rate of the process. The
two models represented by differential equations are generated by using the concept of virtual
kinetic parameters, which can be determined from non-isothermal experiments only. A key property
of the virtual parameter "p" involved in the transformation rate equations is that it quantitatively
characterizes the temperature rate dependence of the non-isothermal reaction.
Abstract: In order to simulate the polyhedral grain nucleation in alloys, 3-D cell population growth
processes are studied in space-filling periodic cellular systems. We discussed two different methods
by which space-filling polyhedral cellular systems can be constructed by topological
transformations performed on “stable” 3-D cellular systems. It has been demonstrated that an
infinite sequence of stable periodic space-filling polyhedral systems can be generated by means of a
simple recursion procedure based on a vertex based tetrahedron insertion. On the basis of computed
results it is conjectured that in a 3-D periodic, topologically stable cellular system the minimum
value of the average face number 〈f〉 of polyhedral cells is larger than eight (i.e. 〈f〉 > 8). The
outlined algorithms (which are based on cell decomposition and/or cell nucleation) provide a new
perspective to simulate grain population growth processes in materials with polyhedral
Abstract: Experiments were performed for visual observation and investigation of liquid Gallium
flow at a temperature of 40oC in a rotating magnetic field. Two different measuring methods were
developed to determine the revolution number of rotating melt. In both cases the frequency of
magnetic induction was 50, 100 and 150 Hz and the values of magnetic induction could be changed
between 0 and 70 mT. The magnetic Taylor number changed between 0 and 3.54x107 during the
Abstract: When applying laser transformation hardening (LTH) on a steel part the aim is to harden
a localized area, which results in high hardness value for a defined width and depth of the material.
To assure the hardened zone and keep the maximum temperature of the surface below the melting
point we have used a finite element model (FEM) to compute the solution for heat distributions and
the phase transformation of the material during LTH. Modelling results were used to introduce safe
operating regions for LTH with different processing conditions.
A problem associated with some LTH applications is the necessity to overlap the hardening passes.
The temperature distribution of this phenomenon was also modelled using FEM which truly assist
in finding optimum overlapping and technological parameters.