Ultrafino zrnati niskougljični čelici dobiveni intenzivnom plastičnom 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 – 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 niskougljični čelici dobiveni intenzivnom plastičnom deformacijom. Struktura i svojstva niskougljičnih čelika sa 0,14%C i 0,1% C-B uzeta u dva početna stanja, martenzitnom i feritno-perlitnom, istraživani su poslije hladnog kutno kanalnog prešanja (KKP). KKP postupak dovodi do stvaranja parcijalne submikrokristalne strukture sa veličinom zrna 150-300nm, ovisno od vrste čelika i početnog stanja. Najfinija struktura sa veličinom zrna 190nm dobijena je za 0,1%C-B čelik (mikrolegiran borom). Vlačna čvrstoća ovog čelika poslije KKP-a (Rm=805-1235 MPa), uvrštava ovaj čelik u kvalitetnu skupinu R80 - R120. Za čelik sa 0,14%C dobijena vlačna čvrstoća ga uvrštava do R80

Razvitak intenzivnih plastičnih deformacija (IPD) kontinuiranog procesa za trake i šipkaste 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 plastičnih deformacija (IPD) na nižim temperaturama (ispod temperature rekristalizacije) i neuobičajno poboljšavanje svojstava takovih materijala se pokazalo stvarnim. Međutim, industrijska primjena je ograničena glede nedostatka efektivnog kontinuiranog procesa IPD. Razmatraju se mogućnosti razvitka kontinuiranog IPD procesa na temelju s jedne strane na kutno kanalnom prešanju (KKP), a s druge strane na kontinuiranoj ekstruziji ili procesu vučenja. Analiziraja se i postojanje različitih kontinuiranih IPD procesa za traku, šipkaste proizvode i žicu

Obrada metala intenzivnom plastičnom deformacijom (IPD) – odgovarajuća struktura i mehanička 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 plastičnom deformacijom (IPD) – odgovarajuća struktura i mehanička svojstva. IPD je postupak pretvorbe krupno u ultrafino zrnate (UFZ-a) metale i legure. Dobiveni UFZ materijal posjeduje oplemenjena mehanička i fizikalna svojstva, te su namjenjeni za široko komercijalno rabljenje. Ovaj članak s jedne strane daje osvrt na povijesni razvitak IPD-a postupka, a s druge strane djelomice ishodište za razvitak UFZ-a i njezine stabilnosti u trgovački čistom 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

Mehanička i uporabna svojstva niskougljičnih čelika poslije intenzivne plastične 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 – 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 -40°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 500°C. The strength properties at 600°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 600°C is substantially higher than that of the 0,1% C-Mn-V-Ti steel.Istražena je struktura i svojstva niskougljičnog čelika 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 prešanja (KKP). KKP dovodi do ustroja submikrokristalne strukture s veličinom zrna 150-300 nm. U submikrokristalnom čeliku 0,09% C-Mn-Si-Nb-V-Ti se povećala više od dva puta, a udarna žilavost pri temperaturi ispitivanja -40°C više od tri i pol puta usporedbom s normaliziranom stanju tog čelika. Plastičnost se pri tome nešto smanjuje. Visoka čvrstoća submikrokristalnog čelika 0,1% C-Mn-V-Ti i 0,09% C-Mo-V-Nb zadržava se do temperature ispitivanja 500°C. Vatrootpornost ovih čelika pri 600°C 20-25% je više nego u nedeformiranom stanju. Čvrstoća čelika 0,09% C-Mo-V-Nb pri 600°C je znatno viša nego za čelika 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 °C and 1000 °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 channel’s angle j = 90°, at different temperature in range of 150 - 300 °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]

Ultrafine-grained low carbon steels by severe plastic deformation

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 – 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