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EN
In this work we present the influence of low temperature gallium nitride (LT-GaN) nucleation layer deposition and recrystallization conditions on the electrical and optical properties of buffer and active layer of metal–semiconductor field-effect transistor (MESFET) structure. MESFET structures were used to investigate the properties of bulk materials that determine also the performance of many type GaN based devices, like light emitting diodes (LEDs), high electron mobility transistors (HEMTs) and metal–semiconductor–metal (MSM) detectors. The set of n-GaN/u-GaN/sapphire structures using different nucleation LT-GaN layers thickness and different annealing times was deposited using AIXTRON CCS epitaxial system. In contrast to typical procedure, the high resistive GaN buffer layer was not obtained by intentional Fe/Mg doping, but by specific adjustment of GaN nucleation conditions and recrystallization process parameters that introduce carbon atoms in epitaxial layers, that serve as donors. Generally, low pressure (below 200 mbar) in a reactor chamber, during initial stages of nucleation and recrystallization as well as HT-GaN epitaxy, promotes the growth of high resistive material. Obtained results show that annealing/recrystallization time of LT-GaN has a significant impact on the electrical and optical properties of GaN buffer layers. Longer annealing periods tend to promote crystallization of material with higher electron mobility and higher Si dopant incorporation/activation while maintaining high resistivity in u-GaN buffer area. It was shown that the dimensions of the GaN islands, that could be influenced by the duration of an annealing step of LT-GaN growth, have no impact on the HT-GaN buffer layer coalescence process and material resistivity, but influences mainly electrical properties of active n-GaN layer. Author suggests that the key parameters that are determining the buffer resistivity are the pressure and temperature during LT-GaN annealing and buffer layer coalescence. The influence of GaN island diameters, after LT-GaN annealing, on the u-GaN resistivity was not confirmed.
EN
In this study, the chemical and phase composition of two samples of phosphogypsum from the waste dumps of the Industry of Chemical Products “Elixir – Prahovo” (Serbia) were examined, as well as the possibility of recrystallization of gypsum from an aqueous suspension of phosphogypsum. The negative effect of higher temperatures on the solubility of calcium sulfate (13.08 mmol/dm3 at 95°C vs. 15.43 mmol/dm3 at 40°C) was utilized. In several repeated cycles, calcium sulfate component was progressively dissolved in water at room temperature and then precipitated at 100°C, using the same liquid phase throughout the experiment. Therefore, phosphogypsum was separated into recrystallized (purified) gypsum, insoluble residue and supernatant, and the mass balance for the experiment was calculated. Elemental, XRD and SEM-EDS analyses were performed on raw phosphogypsum, purified gypsum and insoluble residue. The whiteness of raw phosphogypsum and purified gypsum were determined and compared. The main objective of the study was to investigate the nature of insoluble impurities, in order to define and optimize the methods for their removal during a potential industrial processing of phosphogypsum.
PL
W artykule przedstawiono skład chemiczny i fazowy dwóch próbek fosfogipsu ze składowisk odpadów Przemysłu Chemicznego „Elixir – Prahovo” (Serbia), a także możliwość rekrystalizacji gipsu z zawiesiny wodnej fosfogipsu. Wykorzystano negatywny wpływ wyższych temperatur na rozpuszczalność siarczanu wapnia (13,08 mmol/ dm3 w 95°C wobec 15,43 mmol/dm3 w 40°C). W kilku powtarzających się cyklach siarczanu wapnia stopniowo rozpuszczano w wodzie w temperaturze pokojowej, a następnie wytrącano w 100°C, stosując tę samą fazę ciekłą w całym doświadczeniu. W ten sposób fosfogips został rozdzielony na rekrystalizowany (oczyszczony) gips, nierozpuszczalną pozostałość i supernatant, kolejno obliczono bilans masy dla doświadczenia. Analizy elementarne, XRD i SEM-EDS przeprowadzono na surowym fosfogipsie, oczyszczonym gipsie i nierozpuszczalnej pozostałości. Określono i porównano biel surowego i oczyszczonego gipsu. Głównym celem pracy było zbadanie natury nierozpuszczalnych zanieczyszczeń w celu określenia i zoptymalizowania metod ich usuwania podczas przemysłowego przetwarzania fosfogipsu.
3
Content available Friction Weldability of UFG 316L Stainless Steel
EN
The broad range applications of Ultra-Fine Grained metals is substantially limited by the lack of a welding method that allows them to be joined without losing the strong refinement of structure. From this point of view, the solid state welding processes are privileged. Friction welding tests were carried out on UFG 316L stainless steel. A joining process at high temperature activates the recrystallization, therefore the friction welding parameters were selected according to the criterion of the lowest degree of weakness due to recrystallization in the heat affected zone. In order to characterize the structure of basic material and selected areas of the obtained joint, were performed SEM, TEM and metallographic examinations in terms of hardness and range of softening of the material and tensile test. Despite the short time and relatively low welding temperature, results of the test by scanning electron microscopy and transmission electron microscopy confirmed the loss of the primary ultrafine structure in the Heat Affected Zone of welded joint.
EN
The research paper studies the strengthening and the kinetics of recrystallization of ETP copper and OF copper. This research covers a wide scope of strain hardening specific for the manufacturing of microwires (true strain of the order of 5) and the range of temperatures and times of the recrystallization process referring to the real life conditions occurring in advanced technologies of microwires’ manufacturing. As a result of the performed tests, it was established that the recrystallization temperature of ETP copper is lower than the recrystallization temperature of OF copper regardless of the recrystallization time as the recrystallisation effect can be achieved after about 10–30 s regardless of the copper grade.
5
Content available remote Re-crystallization of Silicon during Rapid Thermal Treatment
EN
It is by means of the Auger-spectroscopy, spectral ellipsometry, X-ray diffraction that for the first time an opportunity was shown of applying the rapid thermal treatment for removal of the disrupted layer on the working surface of the silicon wafers after the chemical-mechanical polishing owing to its solid-phase re-crystallization.
PL
Dzięki użyciu spektroskopii Augera, elipsometrii spektralnej oraz dyfrakcji rentgenowskiej po raz pierwszy przedstawiona została możliwość zastosowania szybkiego termicznego usuwania uszkodzonej warstwy na powierzchni roboczej wafli silikonowych, powstałych po chemiczno-mechanicznym polerowaniu, za pośrednictwem jego rekrystalizacji w fazie stałej.
PL
Wyciskane na gorąco pręty ze stopu aluminium AlZn6,43Mg2,23Cu1,78 (AA7010) poddano, kolejno, odkształceniu drogą ciągnienia, wyżarzaniu na stan miękki (O) oraz procesowi utwardzania wydzieleniowego na stan T6. Próbki ciągnionych prętów o zróżnicowanej wielkości odkształcenia (5–67%) poddano wyżarzaniu w szerokim zakresie temperatury (300–465°C) i czasu wyżarzania (1–10 h). Zastosowane warunki wyżarzania aktywizują procesy zdrowienia, rekrystalizacji i rozrostu ziarna. Wykazano, że proces rekrystalizacji prętów, wyżarzanych na stan O, jest kontrolowany przez dystrybucję i stabilność termiczną wydzieleń fazy czynnej η (MgZn2). Wyżarzanie w temperaturze niższej od temperatury granicznej rozpuszczalności fazy czynnej (poniżej 400°C) zachowuje liniowy rozkład wydzieleń tej fazy, co utrudnia migrację frontów rekrystalizacji w kierunku promieniowym prętów i prowadzi do formowania ziaren o dużej anizotropii kształtu. Wzrost temperatury wyżarzania powoduje istotne przyśpieszenie procesu rozpuszczania wydzieleń fazy czynnej, w wyniku czego następuje uwolnienie frontów rekrystalizacji, a w konsekwencji formowanie ziaren o znacznie mniejszej anizotropii kształtu oraz zmiana dystrybucji i morfologii wydzieleń tej fazy. Stwierdzono ponadto, że – pomimo znaczących różnic strukturalnych – wielkość odkształcenia praktycznie nie wpływa na własności wytrzymałościowe i plastyczne prętów zarówno w stanie O, jak i w większości przypadków w stanie T6. Potwierdzono eksperymentalnie słabą zależność własności wytrzymałościowych Al i jego stopów od wielkości ziarna oraz istotny wpływ rodzaju i dystrybucji prowydzieleń (wydzieleń) faz umacniających na własności mechaniczne tych stopów w stanie T6.
EN
The hot extruded rods of aluminum alloy AlZn6,43Mg2,23Cu1,78 (AA7010) were subjected to, in sequence, deformation by drawing, annealing to the O temper and precipitation hardening to the T6 temper. The samples of rods drawn with the variable strain value (area reduction of 5–67%), were annealed in the wide range of temperatures (300–465°C) and times (1–10 h). The applied annealing conditions activate recovery, recrystallization and grain growth processes. It was shown that recrystallization process of rods annealed to the O temper is controlled by a distribution and thermal stability of active phase η (MgZn2). The annealing at the temperatures lower than the temperature of active phase solubility limit (below 400°C) maintains a linear distribution of this phase precipitates. It hinders recrystallization fronts migration in radial direction of rods and leads to formation of grains with considerable shape anisotropy. The increase of annealing temperature results in significant acceleration of the active phase precipitates dissolution process, whereby a release of recrystallization fronts and in consequence formation of grains with appreciable lower shape anisotropy, as well as change of distribution and morphology of mentioned phase precipitates take place. Moreover, it was found that – despite considerable structural differences – strain value during drawing hardly influences strength and plastic properties of the rods in the O temper, as well as in the most cases in the T6 temper. The weak relationship between grain size and strength properties of Al and its alloys, as well as significant influence of hardening phases pre-precipitates (precipitates) type and distribution on mechanical properties of these alloys in the T6 temper were experimentally confirmed.
EN
The preliminary results of 57Fe Mössbauer spectroscopy and X-ray diffraction (XRD) of fully metamict samarskite dated at ~1500 Ma, which absorbed -dose of 6.5 × 1017 α-decay mg–1, are reported after one-hour annealing at 673, 873, 1173 and 1373 K in argon atmosphere. Metamict minerals contain radioactive elements that degrade their crystal structures over geological time. All the Mössbauer spectra obtained can be fitted to two quadrupole doublets assigned to Fe2+ and Fe3+ in octahedral positions. The relative contribution of Fe2+ (Fe2+/Fe) reaches a minimum of 0.10 at 1173 K.
EN
The annealing behavior of AA1050 aluminum alloy deformed by equal-channel angular pressing (ECAP) was studied experimentally. The material was subjected to extrusion through die with channels intersecting at an 90° angle. Samples were pressed for up to 8 passes using route BC, then cut into slices and subsequently annealed for 1 hour at temperatures from 100°C to 350°C. Hardness measurements were performed on each slice. Microstructure of material was analyzed in the longitudinal section by means of Electron Backscatter Diffraction system in a scanning electron microscope (EBSD/SEM). From the obtained sets of Kikuchi diffraction patterns orientation maps and Image Quality maps were determined. Grain size, disorientation distributions and crystallographic texture were also estimated. ECAP caused significant improvement of hardness, with stabilization after 4 passes. Refinement of microstructure was obtained with the increasing amount of passes. Material properties were stable during annealing at temperatures lower than 150°C. Annealing at higher temperatures caused a decrease in hardness corresponding to an increase of the grain size.
EN
The paper presents the results of research concerning the influence of hot plastic working parameters on the deformability and microstructure of a Ni-Fe superalloy. The research was performed on a torsion plastometer in the range of temperatures of 900-1150°C, at a strain rates 0.1 and 1.0 s-1. Plastic properties of the alloy were characterized by the worked out flow curves and the temperature relationships of flow stress and strain limit. The structural inspections were performed on microsections taken from plastometric samples after so-called “freezing”. The stereological parameters as the recrystallized grain size, inhomogenity and grain shape have been determined. Functional relations between the Zener-Hollomon parameter and the maximum yield stress and the average grain area have been developed and the activation energy for hot working has been estimated.
PL
W artykule porownano wpływ mieszanek stabilizujących na przebieg procesu rekrystalizacji w sorbetach truskawkowych bezpośrednio po przygotowaniu oraz po miesiącu przechowywania w temp. -18°C. Do badań wykorzystano zdjęcia kryształów lodu wykonane za pomocą mikroskopu i kamery Nikon przystosowanych do pracy w ujemnej temperaturze. Następnie zdjęcia przeanalizowano stosując program NIS Elements D i określono wymiary średnic powstałych kryształów lodu. W badaniu jako dodatki stabilizujące zastosowano preparaty żelatyny wieprzowej, gumy guar, gumy ksantanowej, mączki chleba świętojańskiego, kappa-karagenu oraz alkoholu, naturalne białko ochronne AFP i przemysłową mieszankę stabilizatorów oznaczaną jako CRE. Stwierdzono, że dodatek AFP (w połączeniu z żelatyną i gumą guar) oraz mieszanka CRE najskuteczniej hamowały proces rekrystalizacji, a kryształy lodu po miesiącu przechowywania nie były większe niż 15 μm.
EN
The aim of the present paper was to evaluate and compare the effect of stabilizing mixtures on the run of recrystallization process in strawberry sorbet directly after preparation and after a month of storage at -18°C, using a microscope and a Nikon camera adapted to take pictures at the temperature below zero. The images were then analyzed, using NIS Elements D program to determine equivalent ice crystals’ diameters. In the present study, gelatin, guar gum, xanthan, locust bean gum, κ – carrageenan, alcohol, and natural protective protein, called AFP and the mixtures of stabilizers under the trade name CRE were used as stabilizing additives. It was found that the addition of AFP (in combination with gelatin and guar gum) and CRE mixture inhibited most effectively the recrystallization process and the ice crystals after one month of storage did not exceed 15 μm.
EN
This paper describes some recent trends in metal forming such as isothermal forging of titanium aluminides and process combinations between metal forming and additive manufacturing. These trends rely on accurate process and material models for process design. Process and material models must hence be able to track the microstructure evolution in complex materials such as titanium aluminides as well as predict the microstructure evolution along process histories with multiple deformation and/or heat input steps. In models for such processes, JMAK-type kinetics for and phase transformation are still common. For processes involving deformation and heat, the accuracy, consistency and limits of JMAK-type models are discussed. It is shown that the consistency of DRX models as well as the stability of model predictions in multi-stage processes require further attention.
12
EN
The main goal of the paper is dedicated to proper arrangement of the Finite Element (FE) and Random Cellular Automata (RCA) methods in order to develop numerical model of dynamic recrystallization (DRX) and therefore to simulate microstructure morphology changes during plastic deformation at elevated temperatures. In the approach, Finite Element solver provides information on equivalent stress and strain fields after subsequent time steps. Then these data are transferred to RCA model, which is responsible for evaluation of corresponding microstructure morphology evolution and dislocation density changes. Finally, information from the CA part is send back to the FE solver as an input for the next time step. As a result, a fully coupled RCAFE model to simulate progress of DRX is established. The present paper is directly focused on development of algorithms and methods to transfer input/output data between both FE and RCA models. The developed communication protocol is based on the Abaqus VUMAT subroutine. Examples of obtained results from the developed model are also presented to highlight its potential.
PL
W pracy przedstawiono wyniki badań efektów walcowania wysokotemperaturowego taśm ze stopu na osnowie fazy międzymetalicznej Ni3Al z dodatkami stopowymi cyrkonu i boru. Proces odkształcania plastycznego realizowano w dwóch etapach, w temperaturze 1000 i 1100OC z prędkością obwodową walców roboczych 4, 10 i 15 m/min. Efekty przebudowy struktury obserwowano przy użyciu skaningowej mikroskopii elektronowej sprzężonej z układem do analizy dyfrakcji elektronów wstecznie rozporoszonych (EBSD), a także wykonano pomiary twardości. Stwierdzono przebudowę struktury taśm na drodze rekrystalizacji dynamicznej, której udział rósł wraz ze wzrostem prędkości i temperatury walcowania. Najsilniejsze efekty dynamicznej odbudowy struktury (powyżej 50% objętości taśm z parametrem GOS < 2O) obserwowano po drugim etapie walcowania wysokotemperaturowego realizowanego w temperaturze 1100OC z prędkością 15 m/min.
EN
The results of high temperature rolling of Ni3Al-based strips with zirconium and boron addition are shown in the paper. The deformation process was realized by two step rolling at temperature 1000 and 1100OC, with a speed: 4, 10 or 15m/min. The effects of Ni3Al strips structure rebuilding were observed by using a scanning electron microscopy coupled with an electron backscatter diffraction system (EBSD) and a hardness tests were done. The effects of growing up participation of recrystallization with rising a temperature and speed rolling were obtained. The largest effects of dynamic processes of structure recovery (approx. 50% of alloy volume with GOS < 2O) was observed after the second stage of the high temperature rolling conducted at the temperature of 1100°C with the speed of 15 m/min.
14
Content available Microstructure of Hot-Deformed Cu-3Ti Alloy
EN
In the paper, results of investigations regarding temperature and strain rate effects on hot-deformed Cu-3Ti alloy microstructure are presented. Evaluation of the alloy microstructure was performed with the use of a Gleeble HDS-V40 thermal-mechanical simulator on samples subjected to uniaxial hot compression within 700 to 900ºC and at the strain rate of 0.1, 1.0 or 10.0 s-1 until 70% (1.2) strain. It was found that within the analyzed temperature and strain rate ranges, the alloy deformation led to partial or complete recrystallization of its structure and to multiple refinement of the initial grains. The recrystallization level and the average diameter of recrystallized grains increase with growing temperature and strain rate. It was shown that entirely recrystallized, fine-grained alloy structure could be obtained following deformation at the strain rate of min 10.0 s-1 and the temperature of 800°C or higher.
PL
Celem niniejszej publikacji jest opracowanie i implementacja wysokowydajnego systemu do identyfikacji parametrów modelu rekrystalizacji opartego na metodzie automatów komórkowych z wykorzystaniem podejścia analizy odwrotnej. Założenia algorytmu odwrotnego z uwzględnieniem zastosowanych metod optymalizacji zostały przedstawione w pierwszej części pracy. Następnie opisano wykorzystany w trakcie badań model rekrystalizacji oparty na metodzie automatów komórkowych. Ostania część pracy zawiera wyniki przeprowadzonej identyfikacji oraz ich porównanie z wynikami badań eksperymentalnych.
EN
Subject of this work is development and implementation of high-efficiency system for parameter identification of recrystallization models based on cellular automata method with inverse analysis methods. Main assumption of the inverse algorithm are presented first. Particular attention is put on description of optimization technique used during the research. Then major assumptions of the model of recrystallization based on cellular automata method are provided. Finally, results from model parameters identification procedure realized with the developed approach are presented and compared with experimental results.
EN
The main aim of the studies presented in paper was to optimize the parameters of the recrystallisation annealing process used in the course of cold plastic working of high carbon steel for patented wires. Object of the research described in the work was eutectoid steel of 0,8% content of C designated for production of colddrawn wires applied for reinforcement of car tires, hoses and ropes. The results of tests show that the condition of the material and mainly degree of plastic deformation has a clearly influence on the effectiveness of pearlitic steel recrystallisation.
EN
Modeling of the manufacturing process of thin wires made of MgCa08 alloy is described in the paper. This process is composed of 25 drawing passes in heated dies for initial wire diameter of 1.0 mm and final diameter of 0.1 mm. Parameters of drawing process were chosen in such a way that complete recrystallization of the wireoccurred in all passes. The model of static recrystallization (SRX) for MgCa08 alloy was developed to enable design of the drawing process. The parameters of the model were determined on the basis of stress relaxation tests. The tests were performed on GLEEBLE 3800 physical simulator for three temperatures 250, 300, 350ºC and three strains 0.1, 0.2 and 0.3. SRX model was implemented into Drawing2D software, which allows simulation of drawing processes in heated dies. Two variants of drawing process were simulated. In the first variant all passes were performed with the die temperature of 350ºC. In the second variant one pass were carried out with the die temperature of 21ºC. The verification of simulations was done on the basis of microstructures observed in experiments and it was showed in the paper that the model predicts correctly final microstructure. Performed experiments and numerical simulations showed that contribution of the dynamic recrystallization is small and it may be neglected in simulation of multi-pass hot drawing of MgCa08 alloy. The results of simulations of the SRX showed that in this process only every second pass has to be realized in a hot die. After each cold pass the hot pass is required in order to restore the plasticity by recrystallization.
PL
Praca poświęcona jest modelowaniu numerycznemu procesu ciągnienia cienkich drutów ze stopu magnezu MgCa08. Opisywany proces składa się z 25 przepustów wykonanych w gorących ciągadłach przy początkowej średnicy drutu 1 mm oraz końcowej .1 mm. Parametry procesu ciągnienia dobrano w taki sposób, by w czasie ciągnienia zachodziła pełna rekrystalizacja. Dlatego konieczne było opracowanie modelu rekrystalizacji statycznej (SRX). Parametry modelu SRX określono na podstawie badań taksacji, które zostały wykonane na symulatorze GLEEBLE 800 dla trzech różnych temperatur 250, 300, 350 °C i trzech wartości odkształcenia 0.1, 0.2 oraz 0.3. Model rekrystalizacji statycznej został zaimplementowany do oprogramowania Drawing2D, które umożliwia symulację procesu ciągnienia w podgrzewanych ciągadłach. Wykonano dwa warianty symulacji procesu ciągnienia. W pierwszym wszystkie przepusty w procesie ciągnienia zostały wykonane w temperaturze 50 °C, w drugim zaś jeden z przepustów wykonano w temperaturze pokojowej. Weryfikacja modelu rekrystalizacji została wykonana w oparciu o zdjęcia mikrostruktur drutów po procesie ciągnienia. Przeprowadzone badania doświadczalne i symulacje numeryczne wykazały, że udział rekrystalizacji dynamicznej w badanym procesie jest niewielki i może ona zostać pominięta w modelu. Wyniki symulacji rekrystalizacji statycznej pokazały, że w procesie wielostopniowego ciągnienia drutów ze stopu MgCa08 wystarczy, jeżeli co drugi przepust jest wykonywany w podgrzewanym ciągadle. Po każdym przepuście w temperaturze otoczenia wymagany jest przepust w podgrzewanym ciągadle.
EN
Bulk metal forming processes range from processes with a single deformation step such as certain closed-die forging operations to processes with many subsequent stages such as hot rolling, ring rolling or open die forging. Modelling of these manufacturing processes requires both precise process models as well as adequate material models. Microstructure evolution by recrystallization is decisive in all of these processes since the microstructure determines the flow stress and hence the forming forces but it also influences the product properties. In this context, the propagation of variations in the processing conditions and in the material behavior are of special importance and methods for the quantification of uncertainties and their effect on model predictions are required. Such questions can be approached using models of different complexity on various scales as shown in the following examples: In closed die forging of a gear wheel from 25MoCr4 alloy the complex geometry requires a Finite Element process model which in this case is combined with a JMAK type material model. In plate rolling a simplified process model can be applied successfully. Based on the slab theory, which is enhanced for spatial resolution of shear strain using a meta model derived by FEM, this model can simulate even longer roll pass schedules within seconds and offers the possibility to combine it with numerical optimization techniques. Recrystallization of a high-manganese steel in interpass times between hot rolling passes is an example where models with spatial resolution (CP-FEM and phase field) are combined on the micro-scale to predict the recrystallization kinetics based on physically meaningful variables such as grain boundary mobility. In ring rolling the process model must include the closed-loop control system of the rolling machine to achieve a realistic prediction of the process kinematics. Feedback control loops for up to eight kinematic degrees of freedom (velocities and positions of all radial, axial and guiding rolls) have been defined using virtual sensors integrated in the simulation. Offline coupling with microstructure simulation is used to predict the final grain size and determine under which conditions static recrystallization occurs during the rolling sequence.
EN
This paper presents an overview of methods for recrystallizing 3-nitro- 1,2,4-triazol-5-one (NTO), with particular emphasis on methods for obtaining spheroidal particles with low porosity. The effects of selected solvents and surfactants on the recrystallization results was checked. Products in the form of spheroidal particles were obtained for some selected solvent-surfactant systems. The bulk density, surface area, size distribution, and sensitivity to friction and impact were tested for the spherical NTO samples and thermal analysis was also performed.
EN
Use of the protective steel capsules enabled to manage the laboratory hot flat rolling of the extremely brittle as-cast aluminide Fe-40at.%Al-Zr-B with the total height reduction of almost 70 %. The hot rolling parameters were optimized to obtain the best combination of deformation temperature (from 1160°C up to 1240°C) and rolling speed (from 0.14 m·s−1 to 0.53 m·s−1). The resistance against cracking and refinement of the highly heterogeneous cast microstructure were the main criteria. Both experiments and mathematical simulations based on FEM demonstrated that it is not possible to exploit enhanced plasticity of the investigated alloy at low strain rates in the hot rolling process. The heat flux from the sample to the working rolls is so intensive at low rolling speed that even the protective capsule does not prevent massive appearance of the surface transverse cracking. The homogeneity and size of product’s grain was influenced significantly by temperature of deformation, whereas the effect of rolling speed was relatively negligible. The optimal forming parameters were found as rolling temperature 1200°C and the rolling speed 0.35 m·s-1. The effective technology of the iron aluminide Fe-40at.% Al-Zr-B preparation by simple processes of melting, casting and hot rolling was thus established and optimized.
PL
Zastosowanie ochronnych stalowych kapsuł pozwoliło na przeprowadzenie laboratoryjnego walcowania na gorąco pasm z niezwykle kruchego odlewanego aluminidku żelaza (stopu na osnowie fazy międzymetalicznej) Fe-40at.%Al-Zr-B, które umożliwiło redukcję wysokości o prawie 70%. Parametry walcowania na gorąco były dostosowywane celem uzyskania korzystnego zakresu temperatury odkształcenia (od 1160°C do 1240°C) oraz prędkości walcowania (od 0.14 m·s−1 do 0.53 m·s−1) dla otrzymania pasma bez pęknięć i rozdrobnienia silnie niejednorodnej mikrostruktury odlewu. Zarówno eksperymenty jak i matematyczne symulacje oparte na MES wykazały, że niemożliwe jest uzyskanie dobrej plastyczności badanego stopu przy niskich prędkościach odkształcenia podczas walcowania na gorąco. Strumień ciepła płynący z próbki na walce jest tak intensywny przy małej prędkości walcowania, że nawet kapsuła ochronna nie zapobiega pojawieniu się powierzchniowych pęknięć poprzecznych. Jednorodność i rozmiar ziarn w materiale silnie zależy od temperatury odkształcenia, podczas gdy wpływ prędkości walcowania jest relatywnie niewielki. Optymalne parametry kształtowania stopu to: temperatura 1200°C oraz prędkość walcowania 0.35 m·s−1. Skuteczna technologia przygotowania aluminidku żelaza Fe-40at.%Al-Zr-B w prostym procesie topienia, odlewania i walcowania na gorąco została w ten sposób ustalona i zoptymalizowana.
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