scholarly journals Prediction of Epitaxial Grain Growth in Single-Track Laser Melting of IN718 Using Integrated Finite Element and Cellular Automaton Approach

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5202
Author(s):  
Amir Reza Ansari Dezfoli ◽  
Yu-Lung Lo ◽  
M. Mohsin Raza
Keyword(s):  
Grain Size ◽  
Finite Element ◽  
Grain Growth ◽  
Heat Input ◽  
Single Track ◽  
Laser Melting ◽  
Melt Pool ◽  
Initial Substrate ◽  
Average Grain Size ◽  
Epitaxial Grain Growth

The mechanical properties of selective laser melting (SLM) components are fundamentally dependent on their microstructure. Accordingly, the present study proposes an integrated simulation framework consisting of a three-dimensional (3D) finite element model and a cellular automaton model for predicting the epitaxial grain growth mode in the single-track SLM processing of IN718. The laser beam scattering effect, melt surface evolution, powder volume shrinkage, bulk heterogeneous nucleation, epitaxial growth, and initial microstructure of the substrate are considered. The simulation results show that during single-track SLM processing, coarse epitaxial grains are formed at the melt–substrate interface, while fine grains grow at the melt–powder interface with a density determined by the intensity of the heat input. During the solidification stage, the epitaxial grains and bulk nucleated grains grow toward the top surface of the melt pool along the temperature gradient vectors. The rate of the epitaxial grain growth varies as a function of the orientation and size of the partially melted grains at the melt–substrate boundary, the melt pool size, and the temperature gradient. This is observed that by increasing heat input from 250 J/m to 500 J/m, the average grain size increases by ~20%. In addition, the average grain size reduces by 17% when the initial substrate grain size decreases by 50%. In general, the results show that the microstructure of the processed IN718 alloy can be controlled by adjusting the heat input, preheating conditions, and initial substrate grain size.

scholarly journals Modelling Microstructure Evolution in ATI 718Plus® Alloy

2016 ◽  
Vol 716 ◽  
pp. 352-359
Author(s):  
Aleksey Reshetov ◽  
Olga Bylya ◽  
Michal Gzyl ◽  
Malgorzata Rosochowska ◽  
Paul Blackwell
Keyword(s):  
Finite Element Analysis ◽  
Grain Size ◽  
Finite Element ◽  
Grain Growth ◽  
Microstructure Evolution ◽  
Deformation Process ◽  
Main Trend ◽  
Main Body ◽  
Element Analysis ◽  
Average Grain Size

The present study details the results of finite element analysis (FEA) based predictions for microstructure evolution in ATI 718Plus® alloy during the hot deformation process. A detailed description of models for static grain growth and recrystallisation is provided. The simulated average grain size is compared with those experimentally measured in aerofoil parts after forging trials. The proposed modified JMAK model has proved to be valid in the main body of the forging. The results predicted for the surface are less accurate. The recrystallised grain size on the surface is smaller than in the centre of the part which corresponds to the experimental results and reflects the main trend.

Local Mechanical Properties of a Magnesium Hood Inner Component Formed at Elevated Temperature

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Vesna Savic ◽  
Louis G. Hector ◽  
Sooho Kim ◽  
Ravi Verma
Keyword(s):  
Grain Size ◽  
Finite Element ◽  
True Strain ◽  
Local Strain ◽  
Tensile Specimen ◽  
Finite Element Simulations ◽  
Image Correlation ◽  
Specimen Thickness ◽  
Average Grain Size ◽  
Tensile Data

There is considerable worldwide interest in magnesium (Mg) sheet as a replacement for heavier steel and aluminum alloys in vehicle closure components. As Mg gains acceptance in the automotive industry, there will be an increasing demand for accurate material properties for finite element simulations of Mg structures. In this paper, we investigate the extent to which average grain size and postformed tensile properties vary across a Mg AZ31B hood inner component formed at 485°C for 20 min under a constant gas pressure. Tensile specimens were extracted from six regions of the hood inner, which underwent varying degrees of thinning. A state-of-the-art digital image correlation (DIC) algorithm and custom image acquisition software provided true stress-true strain data for each specimen. Tensile data acquired during room temperature testing was compared with that from baseline (undeformed) Mg AZ31B in a fully recrystallized condition (O-temper). Due to its importance in finite element simulations, particular emphasis was placed on the variation of postformed yield strength with specimen thickness and average grain size. Finally, we compute local strain fields during fracture in a tensile specimen with DIC grids positioned in the failure region.

Effect of WO3 Doping on Microstructural and Electrical Properties of ZnO-Pr6O11 Based Varistor Materials

2013 ◽  
Vol 591 ◽  
pp. 54-60
Author(s):  
Xiu Li Fu ◽  
Yan Xu Zang ◽  
Zhi Jian Peng
Keyword(s):  
Grain Size ◽  
Electrical Properties ◽  
Grain Growth ◽  
Doping Level ◽  
Nonlinear Coefficient ◽  
Current Voltage ◽  
Average Grain Size ◽  
Current Voltage Characteristics ◽  
Voltage Performance

The effect of WO3doping on microstructural and electrical properties of ZnO-Pr6O11based varistor materials was investigated. The doped WO3plays a role of inhibitor in ZnO grain growth, resulting in decreased average grain size from 2.68 to 1.68 μm with increasing doping level of WO3from 0 to 0.5 mol%. When the doping level of WO3was lower than 0.05 mol%, the nonlinear current-voltage characteristics of the obtained varistors could be improved significantly with increasing amount of WO3doped. But when the doping level of WO3became higher, their nonlinear current-voltage performance would be dramatically deteriorated when more WO3was doped. The optimum nonlinear coefficient, varistor voltage, and leakage current of the samples were about 13.71, 710 V/mm and 13 μA/cm2, respectively, when the doping level of WO3was in the range from 0.03 to 0.05 mol%.

Nanostructure Evolution of ZnO in Ultra-fast Microwave Sintering

2011 ◽  
Vol 691 ◽  
pp. 65-71 ◽  
Author(s):  
Rodolfo F. K. Gunnewiek ◽  
Ruth Herta Goldsmith Aliaga Kiminami
Keyword(s):  
Grain Size ◽  
Zinc Oxide ◽  
Grain Growth ◽  
Microwave Sintering ◽  
High Heating Rate ◽  
Heating Rates ◽  
Grain Sizes ◽  
Average Grain Size ◽  
Conventional Sintering ◽  
Holding Temperature

Grain growth is inevitable in the sintering of pure nanopowder zinc oxide. Sintering depend on diffusion kinetics, thus this growth could be controlled by ultra-fast sintering techniques, as microwave sintering. The purpose of this work was to investigate the nanostructural evolution of zinc oxide nanopowder compacts (average grain size of 80 nm) subjected to ultra-rapid microwave sintering at a constant holding temperature of 900°C, applying different heating rates and temperature holding times. Fine dense microstructures were obtained, with controlled grain growth (grain size from 200 to 450nm at high heating rate) when compared to those obtained by conventional sintering (grain size around 1.13µm), which leads to excessively large average final grain sizes.

The Study on TiAl Based Alloy Blade Casting Structure by Bottom Pouring Vacuum Suction Casting

2013 ◽  
Vol 442 ◽  
pp. 44-47
Author(s):  
Xi Cong Ye ◽  
Wei Guang Zhao
Keyword(s):  
Grain Size ◽  
Fine Structure ◽  
Grain Growth ◽  
Vacuum Suction ◽  
Suction Casting ◽  
Average Grain Size ◽  
B2 Phase ◽  
Blade Casting ◽  
Forced Cooling ◽  
Undercooling Degree

In this paper, the bottom pouring vacuum suction casting is used, and the TiAl-based alloy blade with good face quality was obtained. Bottom pouring vacuum suction casting obtained Ti-47Al-5Nb-0.5Si alloy fine structure, the average grain size is 20um or less. Metal permanent forced cooling effect increases the undercooling degree, and the formation of Ti5Si3 can hinder the grain growth and the formation of nucleation particles, and Nb elements are conducive to the formation of B2 phase, and these three reasons refined the grain size.

Effect of rate controlled sintering on microstructure and electrical properties of ZnO doped with bismuth and antimony oxides

1997 ◽  
Vol 12 (9) ◽  
pp. 2447-2454 ◽  
Author(s):  
Gaurav Agarwal ◽  
Robert F. Speyer
Keyword(s):  
Grain Size ◽  
Liquid Phase ◽  
Grain Growth ◽  
Elevated Temperatures ◽  
Antimony Oxide ◽  
Second Phase ◽  
Dopant Content ◽  
Average Grain Size ◽  
Rate Controlled ◽  
Grain Boundary Pinning

Various rate controlled sintering (RCS) schedules were used on isostatically pressed particulate compacts of ZnO with Bi2O3 and Sb2O3 additives. For low additive content, smaller average grain sizes with more rapid RCS schedules were attributable to thermal schedules which minimized the time at elevated temperatures where grain growth could occur. β–Bi2O3, Zn7Sb2O12, and Zn2Sb3Bi3O14 phases formed during/after sintering. Elevated heat-treatment temperatures favored the formation of Zn7Sb2O12 and additional β–Bi2O3, while Zn2Sb3Bi3O14 was dominant in sintered samples where the RCS schedule did not result in temperatures in excess of 1100 °C. Zn2Sb3Bi3O14 precipitated during sintering, functioning as grain boundary pinning sites which impeded ZnO grain growth. Bismuth and antimony oxide-based liquid facilitated sintering at lower temperatures, which in turn resulted in decreased average grain size. Rapid RCS schedules for samples with low dopant content resulted in lower sintering temperatures, since time was not allowed for Zn2Sb3Bi3O14 precipitation to deplete the liquid phase. For higher dopant contents, liquid phase was adequately plentiful, wherein longer RCS schedules resulted in lower sintering temperatures. Increasing concentration of second phase generally fostered decreased grain size and attenuated the effect of thermal schedule on the microstructure. Electrical resistance and breakdown voltage increased consistent with decreasing ZnO average grain size.

Ion Induced Grain Growth in Pd

1991 ◽  
Vol 235 ◽  
Author(s):  
D. A. Lilienfeld ◽  
P. Bøorgesen ◽  
P. Meyer
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Grain Growth ◽  
Low Temperatures ◽  
Nanocrystalline Materials ◽  
Ion Irradiation ◽  
Size Distributions ◽  
Careful Choice ◽  
Average Grain Size

ABSTRACTIon irradiation induced grain growth size distributions in Pd are examined at low temperatures. Two features are observed: 1) A majority of the grains saturate in size. 2) Some grains achieve sizes much larger than the average grain size and continue to grow with ion dose. However, by careful choice of ion mass and ion dose, it is possible to produce a sample possessing a monomodal grain size. This process will have applications in producing thin films of nanocrystalline materials.

Annealing Treatment for Superplastic Forming of Twin Roll Casted AZ31 Magnesium Sheet

2011 ◽  
Vol 239-242 ◽  
pp. 50-54 ◽  
Author(s):  
Guo Dong Shi ◽  
Jun Qiao
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Mechanical Test ◽  
Dynamic Balance ◽  
Annealing Treatment ◽  
Optical Microscope ◽  
Grain Structure ◽  
Average Grain Size ◽  
Az31 Sheet ◽  
Twin Roll

Annealing treatments at 200°C, 250 °C, 300°C, and 350°C were conducted on a twin-roll casted AZ31 sheet with an initial average grain size of 10.11 mm. Microstructure and mechanical behaviors were studied by optical microscope observation and tensile mechanical test. Expermeintal results show that grain size experienced three stage evolution during 180 min annealing at each temperature: recrystallization refinement, stabilization under dynamic balance of recrystallization and grain growth, and grain growth. The minimum average grain size of 5.96 μm was achieved after 120 min annealing at 200°C. The refined grain structure causes a decrease of ultimate tensile strength and an increase of elongation, and facilitates superplastic deformation of the material.

Simulation of Ideal Grain Growth Using the Multi-Phase-Field Model

2007 ◽  
Vol 558-559 ◽  
pp. 1177-1181 ◽  
Author(s):  
Philippe Schaffnit ◽  
Markus Apel ◽  
Ingo Steinbach
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Phase Field ◽  
Large Scale ◽  
Field Model ◽  
Three Dimensional ◽  
Phase Field Model ◽  
Two Dimensions ◽  
Von Neumann ◽  
Average Grain Size

The kinetics and topology of ideal grain growth were simulated using the phase-field model. Large scale phase-field simulations were carried out where ten thousands grains evolved into a few hundreds without allowing coalescence of grains. The implementation was first validated in two-dimensions by checking the conformance with square-root evolution of the average grain size and the von Neumann-Mullins law. Afterwards three-dimensional simulations were performed which also showed fair agreement with the law describing the evolution of the mean grain size against time and with the results of S. Hilgenfeld et al. in 'An Accurate von Neumann's Law for Three-Dimensional Foams', Phys. Rev. Letters, 86(12)/2685, March 2001. Finally the steady state grain size distribution was investigated and compared to the Hillert theory.

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