scholarly journals Investigation into microstructure and element segregation of Inconel 713LC during SLM processing using modified cellular automaton model

2021 ◽  
Author(s):  
Amir Ansari Dezfoli ◽  
Yu-Lung Lo ◽  
M. Mohsin Raza
Keyword(s):  
Experimental Investigation ◽  
Energy Density ◽  
Cellular Automaton ◽  
Solid Phase ◽  
Laser Energy ◽  
Crack Density ◽  
Laser Energy Density ◽  
Ca Model ◽  
Solidification Speed ◽  
Element Segregation

Abstract A numerical and experimental investigation is performed into the feasibility of fabricating IN713LC components using selective laser melting (SLM) through an appropriate control of the solidification speed, microstructure formation and element segregation. A modified Cellular Automaton (CA) model is developed to explore the nucleation, grain growth and element segregation behavior of IN713LC during ultra-fast solidification. It is found that the undesired phase formation which occurs during SLM processing of IN713LC is caused by the micro segregation of Nb, Ti, Mo and C at the grain boundaries. It is further shown that the micro segregation intensity depends on the solidification speed, which is determined in turn by the laser energy density. In particular, a lower laser energy density increases the solidification speed and results in a more uniform solid phase, thereby reducing the risk of crack formation. The simulation results are verified by experimental investigation. The results confirm that a lower laser energy density reduces the crack density and crack length. Finally, a crack-free IN713LC SLM sample is successfully produced by reducing the energy density from 360 to 170 J/m.

Temperature Gradient and Heat Conduction of Titanium Alloy during Laser Welding

2010 ◽  
Vol 154-155 ◽  
pp. 42-45
Author(s):  
Ke Rong Zhang ◽  
Jian Xun Zhang
Keyword(s):  
Titanium Alloy ◽  
Heat Conduction ◽  
Liquid Phase ◽  
Energy Density ◽  
Temperature Gradient ◽  
Molten Pool ◽  
Solid Phase ◽  
Laser Energy ◽  
Laser Energy Density ◽  
Heating And Cooling

This paper set a numerical calculation model with local mesh refined for laser welding of titanium alloy applying body heat source model which can accurately describe the shape of keyhole and molten pool on laser welded joint. It calculated the change patterns of the temperature distribution and heat conduction in region of gas, liquid, and solid phase under different laser energy density on the stage of heating and cooling. The results showed that with the increase of the laser energy density t, the dimension of keyhole and molten pool, the temperature gradient and the duration of gas and liquid phase on the stage of heating and cooling are all expected to increase. Under the same laser energy density, temperature gradient has a maximum value in the region of gas phase, secondly is in liquid phase, and minimum in solid phase.

Electrical Properties of Solid Phase Crystallized Silicon Films

2001 ◽  
Vol 664 ◽  
Author(s):  
Tadashi Watanabe ◽  
Hajime Watakabe ◽  
Toshiyuki Sameshima
Keyword(s):  
Heat Treatment ◽  
Electrical Conductivity ◽  
Energy Density ◽  
Laser Irradiation ◽  
Carrier Mobility ◽  
Crystalline Silicon ◽  
Solid Phase ◽  
Laser Energy ◽  
Silicon Films ◽  
Laser Energy Density

ABSTRACTIn this study, the carrier mobility and density for solid phase crystallized (SPC) silicon films fabricated at 600 °C for 48 hours are analyzed by free carrier optical absorption. The carrier mobility is 40 cm2/Vs for SPC films doped with 6×1019-cm−3-phosphorus atoms. This analysis suggests the SPC films have fine crystalline grains closed to single crystalline silicon. In addition, initial carrier density was 3×1019 cm−3, which increased to 6×1019 cm−3by XeCl excimer laser irradiation of 500mJ/cm2. The inactivated regions in SPC films are reduced by laser irradiation. However, the electrical conductivity after laser irradiation for SPC films doped with 6×1018-cm−3-phosphorus atoms decreased from 3.3 to 0.018 S/cm as laser energy density increased to 500mJ/cm2. On the other hand, the electrical conductivity increased from 14.7 to 31.3 S/cm with similar increase of laser energy density after H2O vapor heat treatment at 260°C for 3 hours with 1.3 MPa. Furthermore, the characteristics of n-channel TFTs fabricated with initial SPC films as well as SPC films which was irradiated by laser at 425mJ/cm2 are also researched. The threshold voltage is decreased from 3.8 to 2.0 V by laser irradiation. Threshold voltages of both cases are decreased from 3.8 to 2.4 V for no-laser irradiation and from 2.0 to 0.8 V for laser irradiation, after H2O vapor heat treatment at 310°C for 1 hour with 9.0MPa. Based on the above trial, the defect reduction method combining laser irradiation and H2O vapor heat treatment has proved to be very effective for SPC films and SPC TFTs.

Fundamentals of radiation heat transfer in AlSi10Mg powder bed during selective laser melting

2019 ◽  
Vol 25 (9) ◽  
pp. 1506-1515 ◽  
Author(s):  
Pei Wei ◽  
Zhengying Wei ◽  
Zhne Chen ◽  
Jun Du ◽  
Yuyang He ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Energy Density ◽  
Negative Impact ◽  
Laser Energy ◽  
Melting Process ◽  
Laser Energy Density ◽  
Granular System ◽  
Laser Melting ◽  
Content Type ◽  
Powder Bed

Purpose This paper aims to study numerically the influence of the applied laser energy density and the porosity of the powder bed on the thermal behavior of the melt and the resultant instability of the liquid track. Design/methodology/approach A three-dimensional model was proposed to predict local powder melting process. The model accounts for heat transfer, melting, solidification and evaporation in granular system at particle scale. The proposed model has been proved to be a good approach for the simulation of the laser melting process. Findings The results shows that the applied laser energy density has a significantly influence on the shape of the molten pool and the local thermal properties. The relative low or high input laser energy density has the main negative impact on the stability of the scan track. Decreasing the porosity of the powder bed lowers the heat dissipation in the downward direction, resulting in a shallower melt pool, whereas pushing results in improvement in liquid track quality. Originality/value The randomly packed powder bed is calculated using discrete element method. The powder particle information including particle size distribution and packing density is taken into account in placement of individual particles. The effect of volumetric shrinkage and evaporation is considered in numerical model.

Effects of laser energy density on in situ formation of nano-graphite

2019 ◽  
Vol 48 (5) ◽  
pp. 506004
Author(s):  
刘孝谦 Liu Xiaoqian ◽  
骆 芳 Luo Fang ◽  
杜琳琳 Du Linlin ◽  
陆潇晓 Lu Xiaoxiao
Keyword(s):  
Energy Density ◽  
Laser Energy ◽  
Laser Energy Density ◽  
In Situ Formation

Considerations for Large Area Fabrication of Integrated a-Si and Poly-Si TFTs

1994 ◽  
Vol 336 ◽  
Author(s):  
P. Mei ◽  
G. B. Anderson ◽  
J. B. Boyce ◽  
D. K. Fork ◽  
M. Hack ◽  
...  
Keyword(s):  
Grain Size ◽  
Energy Density ◽  
Laser Energy ◽  
Gate Insulator ◽  
Laser Energy Density ◽  
Laser Crystallization ◽  
Large Area ◽  
Low Leakage ◽  
Threshold Voltages ◽  
Excellent Method

ABSTRACTThe combination of a-Si low leakage pixel TFTs with poly-Si TFTs in peripheral circuits provides an excellent method for reducing the number of external connections to large-area imaging arrays and displays. To integrate the fabrication of the peripheral poly-Si TFTs with the a-Si pixel TFTs, we have developed a three-step laser process which enables selective crystallization of PECVD a-Si:H. X-ray diffraction and transmission electron microscopy show that the polycrystalline grains formed with this three-step process are similar to those crystallized by a conventional one step laser crystallization of unhydrogenated amorphous silicon. The grain size increases with increasing laser energy density up to a peak value of a few Microns. The grain size decreases with further increases in laser energy density. The transistor field effect mobility is correlated with the grain size, increasing gradually with laser energy density until reaching its maximum value. Thereafter, the transistors suffer from leakage through the gate insulators. A dual dielectric gate insulator has been developed for these bottom-gate thin film transistors to provide the correct threshold voltages for both a-Si and poly-Si TFTs.

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