Constitutive Equations for Microstructural Features Developed During Solid Particle Erosion of 52100 Steel

Solid particle erosion of the 52100 bearing steel induced the normal growth of the tempered lath martensite, the low angle boundaries and the recovery islets. Microstructural features were revealed using the electron microscopy. Constitutive equations for the normal growth of the tempered lath martensite, energies of the low angle boundaries, and size of the recovery islets have been derived. The normal growth rate of the tempered lath martensite has been derived from the oriented mobility of the boundary in crystallite-stress fields, the driving force from the boundary energy and the pinning force from the uniformly distributed precipitates. Read-Shockley equation has been redefined using the dislocation density term as the misorientation of the boundary. An advanced Read-Shockley equation has been used for predicting the size of the recovery islets (0.12 mm to 0.27 mm) from the local energy equilibrium of the recovered tempered lath martensite, and validated by the TEM bright field microscopic study

Quantified Static Recovery Trend of Constricted Jogs of Aluminium Alloys During Annealing

The static recovery of dislocations in aluminium alloys is known to observe during re-heating and inter-annealing of aluminium alloys, so that the fully recrystallised and partially recrystallised grain structures are deliberated respectively for a judicious control on their final tempering of strength, ductility, toughness and crystallographic texture to eliminate the earing related problems. An elaborate physical based static recovery simulator is required to address the trend of dislocation recovery during the time of industrial annealing to evaluate the extent of discontinuously and continuously developed recrystallised aluminium alloys. New industrial annealing practices to develop an extensively wide range of aluminium alloys with the medium to low stacking fault energy range, suitable for their plenty of use in defence vehicles, inevitably demand quantified dislocation density, the decisive element of flow strength. The formulated static recovery rate of the constricted dislocation jogs increases with the stacking fault energy and increases with the industrial annealing temperature. The formulated static recovery of dislocations is found to be very precise and concentric to address the process and materials characteristics, so that it would be liable to define the minute change in the processing temperature, i.e. 50K

Development of Cube Recrystallisation Texture and Microstructure of an Aluminium Alloy Suitable for Cartridge Case Manufacturing

Electron backscattered diffraction investigations on just fully recrystallised orientation image microstructures, showed that the cube-oriented grains had the largest size in all microstructures of an aluminium alloy, which have potential use in the cartridge case manufacturing for defence purpose. The simulation of cube microstructure and texture of that aluminium alloy was tried. The recrystallisation texture and microstructure simulation by the 3-D cellular automaton model with the consideration of highest mobility of 40º<111> grainboundary, predicted the volume fraction of the cube texture orientation which was validated by experiment.Defence Science Journal, 2010, 60(3), pp.330-336, DOI:http://dx.doi.org/10.14429/dsj.60.36

Contribution of Process Annealing on the Development of Microstructure and Texture of Cu-30Zn Brass

The present study describes the development of microstructural and textural trends with and without process annealing of the Cu-30Zn brass. Process-annealing refines the grain size and randomizes the crystallographic texture. The best benefits of grain refinement and randomization of texture have been obtained in process-annealing after early stage of deformation. The crucial advantages of (random + Bs) texture strengths in formability of final cold rolled gauges and annealed sheets have also been highlighted

Simulation of primary static recrystallization with cellular operator model

1. Based on the modified cellular automata approach of Reher [60] a cellular operator model has been developed that is capable of accounting for spatial and temporal inhomogeneity on a finer scale. For this a scalable subgrid automaton is introduced that allows for a high spatial resolution on demand and still high computational efficiency. The scalable subgrid permits to track the minute changes of growth front during recrystallization owing to local variations of boundary mobility and net driving force. This approach substantially improves the prediction of grain morphology and grain statistics.2. This new cellular operator model for recrystallization (CORe) has been connected to the grain cluster deformation texture model GIA to account for different nucleation mechanisms. The GIA model renders the deformation texture in terms of grain cluster that in sum properly reflects the deformation texture. Moreover, the GIA model is interfaced to a work hardening model 3IVM that provides information on the dislocation densities of the individual grains in a cluster, depending on the total amount of slip. The individual clusters are evaluated with regards to their behaviour during deformation. Divergence of grain orientation is taken as measure for nucleation in transition band, large stored energy differences (e.g. large difference in dislocation density) across grain boundaries are interpreted as nucleation along grain boundaries and stored energy differences across the deformation zone around the randomly distributed second phase particles are considered as particle stimulated nucleation. Each process contributes specific nucleus orientation. 3. The information on the property of grain to a specific nucleation mechanism is coupled with the information on the local dislocation density to predict the absolute number of nuclei of a specific orientation and location as needed for quantitative recrystallization texture prediction. For this purpose a statistical model for the probability of nucleation sites has been developed based on the imbalance of driving force at interfaces, i.e. grain boundaries or band like structures (transition band). The model renders information on the absolute number of nuclei without adjustable parameters and allows quantitative grain size and texture prediction.4. Since the model has been mainly developed for Al alloys, recovery during annealing was taken into account to reduce the local driving force. Different kinds of recovery mechanisms has been included in this model based on the dislocation climb and cross slip.5. The CORe model has also been interfaced to a microchemistry model (ClaNG) that provides information on the temporal evolution of precipitates volume fraction, precipitate size distribution and solute content in solution. The information is available for any grid element at any time and can be utilized to determine the Zener drag and solute drag at the recrystallization growth front.6. The developed advanced recrystallization model has been subjected to parameter studies to probe the influence of material chemistry and processing conditions on recrystallization kinetics, morphology and texture. In particular their effect on the evolution of cube texture has been investigated.7. In particular, the model predicts a dependency of recrystallization kinetics, grain size and cube intensity on initial grain size. A strong cube texture in the deformed structure and strong growth competition produce a strong cube texture. An increase of the nucleation rate invariably tends to randomize the texture, irrespective of what growth law was used. Good agreement of the model predictions with experimental results has been ascertained

Deformation characterization of cartridge brass

283-288Cu-30 Zn (wt%) alloy is widely used for cartridge case. As received hot rolled (HR) cartridge brass is rolled about 15%, 30%, 40%, and 50% by plane strain rolling at normal room temperature in laboratory. The quantitative microstructure details such as mean grain size and grain size distribution are characterized by optical microscope equipped with microstructure analysis software. The developments of deformation texture are measured by X-ray texture Goniometer and analysis of texture details is done by LaboTex-Edu texture analysis software. The mean grain size is increased with rolling in rolling direction. The grain size distribution shows higher frequency for larger grains with deformation by rolling. The initial stages of rolling produce bi-modal grain size distribution. Later it shifts to multi-modality. The deformation strengthens Bs, L, R, Goss, Taylor, Cu and S texture components. Though the Cu texture orientation shows an increasing trend, the strength of Cu orientation is much less than that of Bs and S components. The transition of texture for Cu, S and Bs texture components is not found in this study