Effect Of Grain Boundary Energy Research Articles

Effect of Grain Boundary Energy in Recrystallization Simulation by Phase Field Method

In this paper, the effect of grain boundary energy in AZ31 Mg alloy with multi-order parameters phenomenological phase field model has been discussed during the progress of recrystallization. The average grain size of the recrystallization grain at a certain temperature and a certain restored energy but various grain boundary energies have been studied, and the simulated results show that the larger the grain boundary energy is, the larger the average grain size will be, and the speed of grain growth will increase with the increase of grain boundary energy. Additionally, temperature will also increase the grain growth rate.

The effect of grain boundary energy on the amorphous forming composition range of Zr–Fe–Al ternary system

Mechanical alloying (MA), as one of the main methods of solid state amorphization (SSA), has been intensively used to prepare amorphous alloys. The composition of alloys and processing conditions of MA is very sensitive for the amorphous forming ability (AFA) or/and amorphous forming composition range (AFCR). During the MA processing, the powder was severely plastically deformed and broken into tiny grains with sub-micro or even nano scale size. In this work, a method for AFCR prediction of ternary system has been proposed based on a thermodynamic point of view and including the size-dependent grain boundary energy. The Gibbs free energy (ΔG) of Zr–Fe–Al system has been calculated with the different grain sizes. Compared with the experimental data, the present calculations are reasonable. The present calculations indicate that the smaller the grain size, the wider AFCR for Zr–Fe–Al system is. The present results also indicate that the higher Fe–Zr content alloys have higher AFA, and grain refinement benefits on extending the AFCR.

Low-temperature degradation in yttria-stabilized tetragonal zirconia polycrystal doped with small amounts of alumina: Effect of grain-boundary energy

Low temperature degradation (LTD) behavior was examined in 3mol% Y2O3-stabilized tetragonal ZrO2 polycrystals (Y-TZP) doped with 0–1.1mol% Al2O3 sintered at 1500°C. 0.12mol% Al2O3-doped Y-TZP exhibited monolithic microstructure without dispersion of Al2O3 grain, while second-phase Al2O3 particles were observed in the Y-TZP sintered bodies doped with 0.54–1.1mol% Al2O3. In the Y-TZP doped with 0.12mol% Al2O3, neither amorphous nor second phase was present along the grain boundaries, but Y3+ and Al3+ ions segregated in the vicinity of the grain boundaries. The tetragonal-to-monoclinic (T→M) phase-transformation rate during the accelerated LTD test significantly decreased at 0.12mol% Al2O3, but the phase-transformation rate slightly increased with the increasing doping amount of Al2O3. The suppressed T→M phase-transformation in Al2O3-doped Y-TZP is explained in terms of decrease in grain-boundary free energy of tetragonal phase owing to Al3+ ions’ grain-boundary segregation.

Influence of grain boundary energy on the nucleation of complexion transitions

To test the effect of grain boundary energy on the nucleation of a transition from a low mobility to a high mobility grain boundary complexion, polycrystalline yttria-doped alumina was sandwiched between two single crystals of sapphire. Thermal groove measurements showed that the distribution of grain boundary energies at the single crystal–polycrystal interface is biased by the single crystal orientation. When annealed above the critical temperature for the complexion transition, the high mobility complexion preferentially nucleated at the higher energy interface.

Probing grain boundary sink strength at the nanoscale: Energetics and length scales of vacancy and interstitial absorption by grain boundaries inα-Fe

The energetics and length scales associated with the interaction between point defects (vacancies and self-interstitial atoms) and grain boundaries in bcc Fe was explored. Molecular statics simulations were used to generate a grain boundary structure database that contained $\ensuremath{\approx}$170 grain boundaries with varying tilt and twist character. Then, vacancy and self-interstitial atom formation energies were calculated at all potential grain boundary sites within 15 \AA{} of the boundary. The present results provide detailed information about the interaction energies of vacancies and self-interstitial atoms with symmetric tilt grain boundaries in iron and the length scales involved with absorption of these point defects by grain boundaries. Both low- and high-angle grain boundaries were effective sinks for point defects, with a few low-$\ensuremath{\Sigma}$ grain boundaries (e.g., the $\ensuremath{\Sigma}3$${112}$ twin boundary) that have properties different from the rest. The formation energies depend on both the local atomic structure and the distance from the boundary center. Additionally, the effect of grain boundary energy, disorientation angle, and $\ensuremath{\Sigma}$ designation on the boundary sink strength was explored; the strongest correlation occurred between the grain boundary energy and the mean point defect formation energies. Based on point defect binding energies, interstitials have $\ensuremath{\approx}$80$%$ more grain boundary sites per area and $\ensuremath{\approx}$300$%$ greater site strength than vacancies. Last, the absorption length scale of point defects by grain boundaries is over a full lattice unit larger for interstitials than for vacancies (mean of 6--7 \AA{} versus 10--11 \AA{} for vacancies and interstitials, respectively).

Simulation of the Effects of Boundary Energy on Microstructure Evolution in Nanocomposite Ceramic Tool Material

A Monte Carlo Potts′ model with different ratios of grain boundary energy is proposed for the sintering process of two-phase nanocomposite ceramic materials. The grain growth process is successfully investigated, and the effect of grain boundary energy on the microstructure is discussed. The simulation results show that the competition between grain boundary and interfacial energies can affect the pinning effect of nano-particles, lead to various microstructure. The simulation results are in accordance with the experiments.

Effect of grain boundary energy on surface-energy induced abnormal grain growth in columnar-grained film

In columnar-grained film with anisotropy in the surface energy, abnormal grain growth occurs to minimize the overall energy. We studied the effect of grain boundary energy on the surface-energy driven abnormal grain growth in thin films using the Monte Carlo computer simulation. Our simulation results show that the growth speed of abnormal growth slows down when grain boundary energy increases. It is because the speed of normal growth driven by the grain boundary energy minimization gets faster with increasing grain boundary energy, while that of the abnormal growth induced by the fixed surface energy is consistent. The growth kinetics was monitored based on the growth velocity of the abnormal grains relative to the average growth velocity of all the grains. It was also found that the abnormal growth kinetics was retarded by impingements among abnormally growing grains when there was more than one abnormal grain.