Papers by Keyword: Normal Grain Growth

Abstract: Texture change during grain growth in Fe-3%Si non-oriented electrical steel was investigated. Cold rolled steel, 0.35mm in thickness, was annealed and recrystallized as an initial structure. Normal grain growth and abnormal grain growth occurred by additional annealing. {111} was dominant in the initial texture. However {100} component, which was not in majority in the initial structure, became stronger after normal grain growth. It was revealed that an average grain size of {100} in the initial structure was bigger than those of other components by analysis of the EBSD data,. Therefore, it is concluded that {100} strengthened after normal grain growth due to its size advantage. On the other hand, {111} components became more stronger after abnormal grain growth. It is inferred that another mechanism of the texture change worked in abnormal grain growth.

Abstract: Grain growth kinetics in an AISI 347 stainless steel with Nb content up to 0.7%wt was studied during the isothermal holding in the temperature range of 1100-1270°C for various periods. Abnormal grain growth was observed even in the presence of a large amount of precipitates. The kinetics of normal grain growth was tracked by metallographic measurements and fitted by the classical modeling, which led to two important parameters of activation energy Q and growth exponent n derived. Both of them are larger than the usual values for grain growth in the Nb-microalloyed steels due to the much larger content of Nb in the present steel.

Abstract: Examination of the SIBM mechanism based on the dislocation substructure at the interior of the Goss oriented grain was carried out by changing the grain size prior to the temper rolling. The following results were obtained. 1) SIBM significantly increased Goss orientation during the eminent grain growth with the initial grain sizes from 18 to 55μm. 2) When the initial grain sizes were large, i.e. 37μm and 55μm, the rolling with the reduction beneath the critical value could not promote SIBM, even the normal grain growth could also be hindered. Consequently a proposal was made that the nucleation of the recovery appeared among substructure domains containing sluggish strain. There exists an adequate size of the domain which varies with the change both of the rolling reduction and the initial grain size.

Abstract: This paper explores the effect of grain size on machining strength in an Fe-Cr-Ni alloy (AISI 316L). Ideal grain growth law [1], was used to obtain the activation energy level for this steel, which was 185 kJ.mol^-1 [2]. The initial grain size was measured (12 μm) and considering these values, both temperature and time values needed to achieve a final grain size ten times larger than the initial one, could be calculated, which were 1200°C and 2 hours. Ternary phase diagram analysis showed that austenite was stable at this temperature. Following, samples of 200 mm length were annealed and quenched in water to prevent any formation of sigma (μ) phase. Annealed and as-received bars were then used to compare their machining strength. Results showed that the machining strength is higher in the as received condition than the one after annealing (127 μm). It may be concluded that the bigger the grain size, the lower its machining strength. It is believed that this is caused by the pile-up of dislocations on grain boundaries, since this material exhibits large plastic deformation before fracture.

Abstract: This paper proposed a new 2D method to simulate the microstructure for normal grain growth of polycrystalline materials. In this method, the sample was discretized into geometry points and a straightforward geometric construction was implemented to estimate whether the current point was located at the interior of a certain grown grain. The ceramics material was assumed isotropic; furthermore, the single-phase and two-phase systems without pores were discussed respectively. So each grain core would grow up at the same velocity in all directions until it met another growing core in single-phase systems, while in two-phase systems, there would be two sorts of cores with different growing velocities. The ratio of these different velocities was the key factor of the sample microstructures after sintering. The simulation results and the analysis showed that the proposed method agree well with the experimental observation.

Abstract: A Monte Carlo algorithm for single-phase normal grain growth has been implemented, which allows one to simulate and observe the temporal development of large grain microstructures in three dimensions. The relaxation process to the self-similar coarsening regime has been studied by following the temporal development of quantities like the average grain size, the standard deviation of the grain sizes and topological correlations.

Abstract: The evolution of crystallographic texture in a Zr-2Hf alloy has been investigated during deformation, primary recrystallisation and normal grain growth. The as-deformed states (50-90% deformation) are characterized by a major tilted {0001}<1010> texture component and this component is reinforced with increasing deformation. A decrease in the intensity of the tilted {0001}<10 10> component and a continuous increase in the intensity of the tilted {0001}<1120 > component take place during primary recrystallisation. Normal grain growth is associated with the coarsening of grains with the {0001}<1120 > orientation. This texture evolution is interpreted on the basis of the evaluation of the stored energy and the consideration of specific grain boundaries with low energy and/or high mobility.

Abstract: The effect of annealing temperature on grain growth, texture development and magnetic properties of Al-free and Al-1% added non-oriented electrical steel were investigated. Normal grain growth occurred in Al-free steel. On the other hand, abnormal grain growth occurred in Al-added steel which was annealed at 800°C for 24h. Precipitates in these two steels were different. TiN precipitated in Alfree steel, but in the case of Al-added steel, AlN and TiC precipitated. The TiC in Al-added steel was so fine that it inhibited the normal grain growth and finally caused the abnormal grain growth. Main textures of both steels were near {111}<112>, but the intensity of near {111}<112> in the abnormal grain growth was higher than that in the normal grain growth. Magnetic flux density (B50/Bs) was decreased by the grain growth. Especially B50/Bs in the abnormal grain growth was lower than that in normal grain growth. B50/Bs in these steels can be estimated by their three-dimensional textures in vector method.

Abstract: Grain growth in the cold rolled and subsequently recrystallized AA 5182 sheets was investigated by means of microstructure observations and texture measurements. Grain growth behavior strongly depends on the annealing temperatures. Grain growth hardly took place at temperatures lower than 470°C, which is attributed to a low mobility of grain boundaries. Abnormal grain growth occurred at temperatures ranging from 480 to 530°C. Annealing above 560°C gave rise to the dissolution of inhibitor precipitates, which led to normal grain growth.

Abstract: A three-dimensional Monte Carlo computer simulation technique has been applied to the problem of normal grain growth. A continuum system is modelled employing a discrete lattice. In this paper we investigate the connectivity of the points that represent the discretized microstructure. The lattice can have a strong influence on the result of the simulation. Only the BCC lattice with 14 neighbours gives similar results than the traditional simple cubic model with 26 neighbours. If we consider the computing time and the required computer memory, the BCC-14 model is a good alternative to the SC-26 model for simulating normal grain growth.