The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Elena V Pereloma - One of the best experts on this subject based on the ideXlab platform.
-
microstructure and micro texture evolution during the Dynamic Recrystallisation of a ni 30fe nb c model alloy
Journal of Alloys and Compounds, 2016Co-Authors: Parvez Mannan, Ahmed A Saleh, Azdiar A Gazder, Gilberto Casillas, Elena V PerelomaAbstract:Abstract The evolution of microstructure and micro-texture during discontinuous Dynamic Recrystallisation of an austenitic Ni-30Fe-Nb-C model alloy subjected to interrupted plane strain compression at strains (e) of 0.23, 0.35, 0.68, 0.85 and 1.2 was investigated using electron backscattering diffraction and transmission electron microscopy. Throughout the strain range, the majority of Dynamic Recrystallisation events comprised nucleation in necklace-like arrangements located at and along grain boundaries via bulging. At e ≥ 0.68, discrete nucleation events were also observed within grain interiors. Grain growth during Dynamic Recrystallisation is characteristic of strain induced boundary migration. The initial texture comprised Cube-RD ({013}〈100〉), Cube-ND ({001}〈310〉) and Cube ({001}〈100〉) orientations. Up to e ≤ 0.35, the unrecrystallised grain fractions comprised the Brass ({110}〈112〉) or Copper ({112}〈111〉) orientations and an intensity spread near Rotated Goss ({011}〈011〉). Between 0.68 ≤ e ≤ 1.2, the texture of the unrecrystallised grain fractions was similar to that of the recrystallised grains throughout the strain range; both of which are dominated by the Cube orientation. The dominance of the Cube orientation in the secondary deformed and recrystallised grains can be ascribed to its low stored energy and orientation stability.
-
the effect of processing parameters on the Dynamic Recrystallisation behaviour of api x70 pipeline steel
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2013Co-Authors: Abdullah Al Shahrani, Azdiar A Gazder, N Yazdipour, Ali Dehghanmanshadi, Cyril Cayron, Elena V PerelomaAbstract:The effect of deformation temperature and strain rate on the Dynamic Recrystallisation (DRX) behaviour of X70 pipeline steel was investigated. DRX parameters such as the critical and peak stresses and strains as well as the deformation activation energy were determined in the temperature range between 925°C and 1125°C for strain rates of 0.1, 1 and 5s-1. The relationship between the peak stresses and strains with the Zener-Hollomon parameter was determined. The Dynamically recrystallised volume fraction was computed as a function of the different temperatures and strain rates. The APRGE software was applied for the first time on electron back-scattering diffraction data of Dynamically recrystallised microstructures in order to reconstruct the prior austenite from the as-quenched martensite phase. The Dynamically recrystallised flow stress curves and microstructure were also predicted using cellular automata modelling. The results show an earlier onset of DRX with a decrease in strain rate or an increase in deformation temperature. The Dynamically recrystallised grain size is also found to decrease with an increase in strain rate and a lowering of deformation temperature. © 2013 Elsevier B.V.
-
effect of austenitising and deformation temperatures on Dynamic Recrystallisation in nb ti microalloyed steel
Materials Science Forum, 2013Co-Authors: Andrii Kostryzhev, Abdullah Al Shahrani, C Zhu, Simon P Ringer, Elena V PerelomaAbstract:An investigation into the influence of the reheat temperature and the austenite deformation temperature on Nb precipitation and Recrystallisation kinetics was carried out for a steel containing 0.081C–0.021Ti–0.064Nb (wt. %). Thermo-mechanical processing was carried out using a Gleeble 3500 simulator. The austenite grain structure was correlated to the dispersive properties of Nb atom clustering and precipitation. Irrespective of the reheat temperature, deformation to 0.75 strain at 1075 °C produced a fully recrystallised austenitic microstructure. After deformation at 975 °C, only partial Recrystallisation was observed in the samples reheated to the higher temperature, whereas samples reheated to the lower temperature were fully recrystallised. The influence of solute drag and particle pinning effects on the Recrystallisation rate is discussed.
Hiroyuki Kokawa - One of the best experts on this subject based on the ideXlab platform.
-
Microstructural evolution and its effect on Hall-Petch relationship in friction stir welding of thixomolded Mg alloy AZ91D
Journal of Materials Science, 2003Co-Authors: Seung Hwan C. Park, Yutaka S. Sato, Hiroyuki KokawaAbstract:Microstructural evolution of a thixomolded magnesium (Mg) alloy AZ91D during friction stir welding was investigated. Friction stir welding resulted in a homogeneous microstructure consisting of fine recrystallised α-Mg grains in the thixomolded material. The microstructural homogenisation and refinement was attributed to Dynamic Recrystallisation accompanied by the dissolution of the eutectic structure during the welding. The grain refinement in the stir zone was effective in increasing the hardness, as predicted by the Hall-Petch equation. The effect of grain size on hardness was smaller than that in conventional and rapidly solidified AZ91. This phenomenon may be explained as being due to the microstructure of the stir zone which consisted of fine equiaxed grains with a high density of dislocations.
-
hall petch relationship in friction stir welds of equal channel angular pressed aluminium alloys
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2003Co-Authors: Y Sato, Mitsunori Urata, Hiroyuki Kokawa, Keisuke IkedaAbstract:Abstract The effect of grain size on hardness in the stir zones of friction stir (FS) welds of equal channel angular (ECA)-pressed Al alloys 1050 and 5083 was examined. The hardness was found to be essentially related to grain size through the Hall–Petch relationship in the stir zone of Al alloy 1050. The k H slope of the Hall–Petch equation for the stir zone of Al alloy 1050 was different from the previously reported ones, which was attributed to Dynamic Recrystallisation during friction stir welding (FSW). On the other hand, the relationship between hardness and grain size in the stir zone of Al alloy 5083 was expressed by the Hall–Petch equation with a change in slope. The change in slope was attributed to the homogeneous distribution of many fine particles.
Y V R K Prasad - One of the best experts on this subject based on the ideXlab platform.
-
processing of iron aluminides
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 1998Co-Authors: R S Sundar, R G Baligidad, Y V R K Prasad, D H SastryAbstract:A processing route comprising of air induction melting (AIM) with protective cover and electroslag remelting (ESR) for production of iron aluminide $(Fe_3Al)$ alloys has been developed. The use of protective cover during AIM results in the minimization of hydrogen gas porosity and a significant reduction in the impurity levels (S, O and N). Attempts have been made to further improve the ductility and hot workability through ESR. The AIM melted with high carbon ingots exhibit excellent tensile properties compared to the low ( 0.074 wt.%) carbon ingots where cracks persist even after ESR. Processing maps were developed for vacuum induction melted as-cast binary and ternary (Cr and Mn) $Fe_3Al$ alloys. Processing maps of $Fe_3Al$ and $Fe_3Al-Cr$ exhibit a Dynamic Recrystallisation domain at temperatures >1123 K. Dynamic Recrystallisation in iron aluminides is controlled by migration of interfaces. In the case of $Fe_3Al-Mn$, Dynamic Recrystallisation is suppressed due to greater resistance to the migration of interfaces. Instead, large grain superplasticity is observed.
-
Dynamic Recrystallisation during hot working of zr 2 center dot 5nb characterisation using processing maps
1996Co-Authors: J K Chakravartty, G K Dey, S Banerjee, Y V R K PrasadAbstract:The characteristics of the hot deformation of Zr-2.5Nb (wt-%) in the temperature range 650-950 degrees C and in the strain rate range 0.001-100 s(-1) have been studied using hot compression testing. Two different preform microstructures: equiaxed (alpha + beta) and beta transformed have been investigated. For this study, the approach of processing maps has been adopted and their interpretation carried out using the Dynamic materials model. The efficiency of power dissipation given by [2m/(m + 1)], where m is the strain rate sensitivity, is plotted as a function of temperature and strain rate to obtain a processing map. A domain of Dynamic Recrystallisation has been identified in the maps of equiaxed (alpha + beta) and beta transformed preforms. In the case of equiaxed (alpha + beta), the stress-strain curves are steady state and the Dynamic Recrystallisation domain in the map occurs with a peak efficiency of 45% at 850 degrees C and 0.001 s(-1). On the other hand the beta transformed preform exhibits stress-strain curves with continuous flow softening. The corresponding processing map shows a domain of Dynamic Recrystallisation occurring by the shearing of alpha platelets followed by globularisation with a peak efficiency of 54% at 750 degrees C and 0.001 s(-1). The characteristics of Dynamic Recrystallisation are analysed on the basis of a simple model which considers the rates of nucleation and growth of recrystallised gains. Calculations show that these two rates are nearly equal and that the nucleation of Dynamic Recrystallisation is essentially controlled by mechanical recovery involving the cross-slip of screw dislocations. Analysis of flow instabilities using a continuum criterion revealed that Zi-2.5Nb exhibits flow localisation at temperatures lower than 700 degrees C and strain rates higher than 1 s(-1).
-
Dynamic Recrystallisation during hot working of zr 2 5nb characterisation using processing maps
Materials Science and Technology, 1996Co-Authors: J K Chakravartty, G K Dey, S Banerjee, Y V R K PrasadAbstract:AbstractThe characteristics of the hot deformation of Zr–2·5Nb (wt-%) in the temperature range 650–950°C and in the strain rate range 0·001–100 s−1 have been studied using hot compression testing. Two different preform microstructures: equiaxed (α+β) and β transformed, have been investigated. For this study, the approach of processing maps has been adopted and their interpretation carried out using the Dynamic materials model. The efficiency of power dissipation given by [2m/(m+1)], where m is the strain rate sensitivity, is plotted as a function of temperature and strain rate to obtain a processing map. A domain of Dynamic Recrystallisation has been identified in the maps of equiaxed (α+β) and β transformed preforms. In the case of equiaxed (α+β), the stress–strain curves are steady state and the Dynamic Recrystallisation domain in the map occurs with a peak efficiency of 45% at 850°C and 0·001 s−1. On the other hand, the β transformed preform exhibits stress–strain curves with continuous flow softening....
-
characterisation of Dynamic Recrystallisation in nickel using processing map for hot deformation
Materials Science and Technology, 1992Co-Authors: N Srinivasan, Y V R K PrasadAbstract:The hot deformation behaviour of polycrystalline nickel has been characterised in the temperature range 750-1200-degrees-C and strain rate range 0.0003-100 s-1 using processing maps developed in the basis of the Dynamic materials model. The efficiency of power dissipation, given by [2m/(m + 1)]. where m is the strain rate sensitivity, is plotted as a function of temperature and strain rate to obtain a processing map. A domain of Dynamic Recrystallisation has been identified, with a peak efficiency of 31% occurring at 925-degrees-C and 1 s-1. The published results are in agreement with the prediction of the processing map. The variations of efficiency of power dissipation with temperature and strain rate in the Dynamic Recrystallisation domain are identical to the corresponding variation of hot ductility. The stress-strain curves exhibited a single peak in a single peak in the Dynamic Recrystallisation domain, whereas multiple peaks and 'drooping' stress-strain curves were observed at lower and higher strain rates, respectively. The results are explained on the basis of a simple model which considers Dynamic Recrystallisation in terms of rates of interface formation (nucleation) and migration (growth). It is shown that Dynamic Recrystallisation in nickel is controlled by the rate of nucleation, which is slower than the rate of migration. The rate of nucleation itself depends on the process of thermal recovery by climb, which in turn depends on self-diffusion.
J J Jonas - One of the best experts on this subject based on the ideXlab platform.
-
influence of Dynamic Recrystallisation on the tensile ductility of steels in the temperature range 700 to 1150 c
Isij International, 1992Co-Authors: B Mintz, R Abushosha, J J JonasAbstract:The role of Dynamic Recrystallisation (DRX) in influencing the hot ductility of plain C-Mn and microalloyed steels was examined by comparing the critical strain for Dynamic Recrystallisation with the fracture strain in a hot tensile test. The temperature range examined was 700 to 1150°C and the strain rates were varied from 3×10–2 to 3×10–4 s–1.For coarse grained plain C-Mn and C-Mn-Al steels solution treated at 1330°C and cooled to the test temperature, the presence at the γ grain boundaries of thin films of deformation induced ferrite at temperatures between the Ae3 and the undeformed Ar3, leads to strain concentrations which give rise to poor ductility. The presence of these thin films prevents the occurrence of DRX. For these steels, the Ae3 temperature, which marks the onset of good ductility is generally high enough to lead to DRX, so that it is not possible to assess its independent contribution to restoring the hot ductility. In coarse grained C-Mn-Nb-Al steels, DRX and the full recovery of ductility are often not observed until the test temperature is higher than 1000°C. This is related to the strain-induced precipitation of NbCN below 1050°C. However, even when Recrystallisation is not possible, the ductility can be improved if the amount of strain-induced NbCN is reduced.For fine grained plain C-Mn and microalloyed steels heated directly to the test temperature, DRX often occurs in the trough. Grain boundary migration rates have to be sufficiently high to prevent crack linkage from occurring, and this often necessitates the resolution and coarsening of particles so that they are no longer effective in pinning the boundaries. Finally, of interest in this work was the observation that as the initial grain size do is refined, its influence in encouraging DRX becomes more marked than that given by the simple do1/2 relationship in the equation ep=Ado1/2Zn, where ep is the critical strain to the peak stress, Z is the Zener-Hollomon parameter and A and n are constants.
-
design of Dynamic Recrystallisation controlled rolling schedules for seamless tube rolling
Materials Science and Technology, 1992Co-Authors: L N Pussegoda, Peter Hodgson, J J JonasAbstract:AbstractA model developed by Sellars and Dutta, for strain induced carbonitride precipitation under isothermal conditions, is extended to precipitation under continuous cooling conditions. It is applied here to laboratory simulations of the stretch reducing stage of a seamless tube mill. The model predictions are compared with experimental observations of the contrasting rolling behaviours of Ti–V and Nb–V steels and excellent agreement is obtained. It is shown that in order to design Dynamic Recrystallisation controlled rolling (DRCR) stretch reducing mill schedules, the critical strain for Dynamic Recrystallisation must be achieved well before the onset of strain induced precipitation. If, however, precipitation begins before the critical strain is reached, then ‘pancaking’ occurs. Thus, Ti–V steels are more suitable for DRCR processing, because strain induced precipitation takes place only at very low temperatures in these materials. As a result, rolling can be carried out at relatively low temperature...
-
design of Dynamic Recrystallisation controlled rolling schedules for seamless tube rolling
Materials Science and Technology, 1992Co-Authors: L N Pussegoda, Peter Hodgson, J J JonasAbstract:Abstract A model developed by Sellars and Dutta, for strain induced carbonitride precipitation under isothermal conditions, is extended to precipitation under continuous cooling conditions. It is applied here to laboratory simulations of the stretch reducing stage of a seamless tube mill. The model predictions are compared with experimental observations of the contrasting rolling behaviours of Ti–V and Nb–V steels and excellent agreement is obtained. It is shown that in order to design Dynamic Recrystallisation controlled rolling (DRCR) stretch reducing mill schedules, the critical strain for Dynamic Recrystallisation must be achieved well before the onset of strain induced precipitation. If, however, precipitation begins before the critical strain is reached, then ‘pancaking’ occurs. Thus, Ti–V steels are more suitable for DRCR processing, because strain induced precipitation takes place only at very low temperatures in these materials. As a result, rolling can be carried out at relatively low temperatur...
Y C Yoo - One of the best experts on this subject based on the ideXlab platform.
-
evolution of Dynamic Recrystallisation in aisi 304 stainless steel
Materials Science and Technology, 2003Co-Authors: S I Kim, C M Lee, S K Hwang, Y C YooAbstract:AbstractThe nucleation and development of Dynamic Recrystallisation (DRX) has been studied via hot torsion testing of AISI 304 stainless steel. The DRX behaviour was investigated with microstructural analysis and slope changes of flow stress curves. The characteristics of serrated grain boundaries observed by SEM, electron backscattered diffraction and TEM indicated that the nucleated DRX grain size was similar to that of the bulged part of the original grain boundary. The DRX of the alloy was nucleated and developed by strain induced grain boundary migration and by the necklace mechanism. Before the steady state in the flow curve at 1000 ° C and 0.5 s-1, the Dynamically recrystallised grains did not remain a constant size and gradually grew to the size of fully DRX grains at steady state (30 μm). The calculation of the grain size was based on X DRX (volume fraction of Dynamically Recrystallisation) under the assumption that the nucleated DRX grains grow to the steady state continuously. It was found that...
-
prediction of Dynamic Recrystallisation behaviour of aisi type 4140 medium carbon steel
Materials Science and Technology, 2002Co-Authors: S I Kim, Y C YooAbstract:AbstractThe aim of the present work was to establish quantitative relationships between the flow stress and the volume fraction of Dynamic Recrystallisation (DRX) as a function of processing variables such as strain rate, temperature, and strain for AISI type 4140 medium carbon steel, by means of torsion tests. Torsion tests were carried out in the temperature range 900-1100°C and the strain rate range 5·0 × 102 -5·0 × 100 s1 to study the high temperature softening behaviour. For the exact prediction of flow stress, the effective stress—effective strain curves were divided into two regions, the work hardening and Dynamic recovery region and the DRX region. The flow stress of the DRX region could be expressed in terms of the volume fraction of DRX. It was found that the calculated results were in agreement with the experimental flow stress and microstructure of the steel for any deformation condition.
