56 research outputs found
Ultrafino zrnati niskougljiÄni Äelici dobiveni intenzivnom plastiÄnom deformacijom
The structure and properties of 0,14% C and 0,1% C - B low-carbon steels taken in two initial states, martensitic and ferritic-pearlitic, were studied after cold equal-channel angular (ECA) pressing. ECA pressing leads to the formation of only partially submicrocrystalline structure with a grain size of 150 ā 300 nm, depending on the steel alloying and initial state. The finest structure with the elements of 190 nm in size is obtained in the 0,1% C - B steel microalloyed with boron. The strength of the 0,1% C - B steel after cold ECA pressing (Rm = 805-1235 MPa) meets the specifications of fasteners of the R80 - R120 strength grade. The strength of the deformed 0,14% C steel is close to the R80 strength grade.Ultrafino zrnati niskougljiÄni Äelici dobiveni intenzivnom plastiÄnom deformacijom. Struktura i svojstva niskougljiÄnih Äelika sa 0,14%C i 0,1% C-B uzeta u dva poÄetna stanja, martenzitnom i feritno-perlitnom, istraživani su poslije hladnog kutno kanalnog preÅ”anja (KKP). KKP postupak dovodi do stvaranja parcijalne submikrokristalne strukture sa veliÄinom zrna 150-300nm, ovisno od vrste Äelika i poÄetnog stanja. Najfinija struktura sa veliÄinom zrna 190nm dobijena je za 0,1%C-B Äelik (mikrolegiran borom). VlaÄna ÄvrstoÄa ovog Äelika poslije KKP-a (Rm=805-1235 MPa), uvrÅ”tava ovaj Äelik u kvalitetnu skupinu R80 - R120. Za Äelik sa 0,14%C dobijena vlaÄna ÄvrstoÄa ga uvrÅ”tava do R80
Razvitak intenzivnih plastiÄnih deformacija (IPD) kontinuiranog procesa za trake i Å”ipkaste proizvode
Grain refinement upon the severe plastic deformation (SPD) at low temperatures (below the recrystallization temperature) and an unusual improvement the properties of such materials are shown reliably. However, the industrial application is limited due to the absence of effective continuous SPD processes. The potential of development of continuous SPD processes based on the equal channel angular pressing (ECAP) process from one side and continuous extrusion or drawing processes from another side is considered. Existing various continuous SPD processes for strip, rod and wire production are analyzed.Usitnjavanje zrna pod utjecajem intenzivnih plastiÄnih deformacija (IPD) na nižim temperaturama (ispod temperature rekristalizacije) i neuobiÄajno poboljÅ”avanje svojstava takovih materijala se pokazalo stvarnim. MeÄutim, industrijska primjena je ograniÄena glede nedostatka efektivnog kontinuiranog procesa IPD. Razmatraju se moguÄnosti razvitka kontinuiranog IPD procesa na temelju s jedne strane na kutno kanalnom preÅ”anju (KKP), a s druge strane na kontinuiranoj ekstruziji ili procesu vuÄenja. Analiziraja se i postojanje razliÄitih kontinuiranih IPD procesa za traku, Å”ipkaste proizvode i žicu
Obrada metala intenzivnom plastiÄnom deformacijom (IPD) ā odgovarajuÄa struktura i mehaniÄka svojstva
SPD methods are used to convert coarse grain metals and alloys into ultrafine grained (UFG) materials. Obtained UFG materials then possess improved mechanical and physical properties which destine them for a wide commercial use. This paper, in one direction, looks into historical development of SPD processes and their effect at obtaining fine crystalline structure, and on the other side also partially focuses on development of UFG structure and its stability in commercial pure aluminium as a function of strain and post-deformation annealing applied.Obrada metala intenzivnom plastiÄnom deformacijom (IPD) ā odgovarajuÄa struktura i mehaniÄka svojstva. IPD je postupak pretvorbe krupno u ultrafino zrnate (UFZ-a) metale i legure. Dobiveni UFZ materijal posjeduje oplemenjena mehaniÄka i fizikalna svojstva, te su namjenjeni za Å”iroko komercijalno rabljenje. Ovaj Älanak s jedne strane daje osvrt na povijesni razvitak IPD-a postupka, a s druge strane djelomice ishodiÅ”te za razvitak UFZ-a i njezine stabilnosti u trgovaÄki Äistom aluminiju, kao funkcija preoblikovanja i poslije deformacije primjenjenog žarenja
Design of Thermo Mechanicaln Processing and Transformation Behaviour of Bulk Si-Mn Trip Steel
In the last decade, a lot of effort has been paid to optimising the thermomechanical processing of TRIP steels that stands for transformation induced plasticity. The precise characterization of the resulting multiphase microstructure of low alloyed TRIP steels is of great importance for the interpretation and optimisation of their mechanical properties. The results obtained in situ neutron diffraction laboratory experiment concerning the austenite to ferrite transformation in Si-Mn bulk TRIP steel specimens, displaying the transformation induced plasticity (TRIP), are presented. The advancement of ferrite formation during transformation in conditioned austenite is investigated at different transformation temperatures and has been monitored using neutron diffraction method. The relevant information on transformation proceeding is extracted from neutron diffraction spectra. The integrated intensities of austenite and ferrite neutron diffraction profiles developed during the transformation are then assumed as a measure of the phase volume fractions of both phases in dependence on transformation temperature and austenite conditioning. According to the yielding information on ferrite volume fractions from isothermal transformation kinetics data the thermo mechanical processing of bulk specimen was designed in order to support austenite stabilization through bainitic transformation. The volume fractions of retained austenite resulting at alternating transformation conditions were measured by neutron and X-ray diffraction respectively. The stability of retained austenite in bulk specimens during room temperature mechanical testing was characterized by in situ neutron diffraction experiments as well
MehaniÄka i uporabna svojstva niskougljiÄnih Äelika poslije intenzivne plastiÄne deformacije
The structure and properties of the 0,09% C-Mn-Si-Nb-V-Ti, 0,1 %C-Mn-V-Ti and 0,09% C-Mo-V-Nb low-carbon steels were studied after cold equal-channel angular pressing (ECAP). ECAP leads to the formation of partially submicrocrystalline structure with a grain size of 150 ā 300 nm. The submicrocrystalline 0,09 %C-Mn-Si-Nb-V-Ti steel compared with the normalized steel is characterized by Re higher more than by a factor of 2 and by the impact toughness higher by a factor of 3,5 at a test temperature of -40Ā°C. The plasticity in this case is somewhat lower. The high-strength state of the submicrocrystalline 0,1% C-Mn-V-Ti and 0,09% C-Mo-V-Nb steels after ECAP is retained up to a test temperature of 500Ā°C. The strength properties at 600Ā°C (i.e. the fire resistance ) of these steels are higher by 20-25 % as compared to those of the undeformed steels. The strength of the 0,09% C-Mo-V-Nb steel at 600Ā°C is substantially higher than that of the 0,1% C-Mn-V-Ti steel.Istražena je struktura i svojstva niskougljiÄnog Äelika 0,09% C-Mn-Si-Nb-V-Ti, 0,1% C-MN-V-Ti i 0,09% C-Mo-V-Nb poslije hladnog kanalno kutnog preÅ”anja (KKP). KKP dovodi do ustroja submikrokristalne strukture s veliÄinom zrna 150-300 nm. U submikrokristalnom Äeliku 0,09% C-Mn-Si-Nb-V-Ti se poveÄala viÅ”e od dva puta, a udarna žilavost pri temperaturi ispitivanja -40Ā°C viÅ”e od tri i pol puta usporedbom s normaliziranom stanju tog Äelika. PlastiÄnost se pri tome neÅ”to smanjuje. Visoka ÄvrstoÄa submikrokristalnog Äelika 0,1% C-Mn-V-Ti i 0,09% C-Mo-V-Nb zadržava se do temperature ispitivanja 500Ā°C. Vatrootpornost ovih Äelika pri 600Ā°C 20-25% je viÅ”e nego u nedeformiranom stanju. ÄvrstoÄa Äelika 0,09% C-Mo-V-Nb pri 600Ā°C je znatno viÅ”a nego za Äelika 0,1% C-Mn-V-Ti
Restoration and Thermal Stability Investigation of Intermetllic Phase in Exposed Nickel Base Superalloy Udimet 500 Turbine Blades
The Udimet 500 nickel base superalloy blade exposed for 50000 hours in land base gas turbine working conditions faced the structure degradation. Six different heat treatments procedures have been applied (the blades were exposed at 900 Ā°C and 1000 Ā°C for different periods with maximum hold of 2500 hours) to rejuvenate the degraded structure. Metallographic work was performed, generally, aging at both temperatures modify the gamma prime size, morphology and distribution characteristics substantially. The volume fraction of secondary gamma prime decreased with increasing aging time
Low Carbon Steel Processed by Equal Channel Angular Warm Pressing
Low carbon steel AISI 10 was subjected to a severe plastic deformation technique called Equal Angular Channel Pressing (ECAP) at different increased temperatures. The steel was subjected to ECAP with channelās angle j = 90Ā°, at different temperature in range of 150 - 300 Ā°C. The number of passes at each temperature was N = 3. Light, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) of thin foils were used to study the formation of substructure and ultrafine grains in deformed specimens. The size of newly born polygonized grains (subgrains and/or submicrocrystalline grains) is in range of 300 - 500 mm. The formation of such of predominant submicrocrystalline structure resulted in significant increase of yield stress [Re] and tensile strength of the steel [Rm]
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