Partial Melting and Resolidification of Single-Component Metal Powder With a Moving Laser Beam

2005 ◽  
Author(s):  
Bin Xiao ◽  
Yuwen Zhang
Keyword(s):  
Melting Point ◽  
Laser Beam ◽  
Partial Melting ◽  
Metal Powder ◽  
Liquid Pool ◽  
Single Component ◽  
Solid Core ◽  
Metal Powders ◽  
Scanning Velocity ◽  
Laser Beam Intensity

Partial melting and resolidification of single-component metal powders with a moving laser beam is investigated numerically. Since laser processing of metal powder is a very rapid process, the liquid layer and solid core of a partially molten powder particle may not at thermal equilibrium and have different temperatures: the temperature of the liquid part is higher than the melting point, and the temperature of the solid core is below the melting point. Therefore, the local temperature of regions with partial molten particles is within a range of temperature adjacent to the melting point, instead of at the melting point. The partial melting of the metal powder is also accompanied by shrinkage that drives out the gas in the powder bed and the powder structure is supported by the solid core of the partially melted powder particles. Melting with shrinkage and resolidification are described using a temperature transforming model. The convection driven by capillary and gravity forces in the melting liquid pool is formulated by using Darcy’s law. The effects of laser beam intensity and scanning velocity on the shape and size of the heat affected zone and molten pool are investigated.

Three-Dimensional Modeling of Laser Sintering of a Two-Component Metal Powder Layer on Top of Sintered Layers

2006 ◽  
Vol 129 (3) ◽  
pp. 575-582 ◽  
Author(s):  
Tiebing Chen ◽  
Yuwen Zhang
Keyword(s):  
Metal Powder ◽  
Laser Scanning ◽  
Three Dimensional ◽  
Laser Sintering ◽  
Powder Layer ◽  
Metal Powders ◽  
Three Dimensional Model ◽  
Scanning Velocity ◽  
Laser Beam Intensity ◽  
Two Component

A three-dimensional model of selective laser sintering of a two-component loose metal powder layer on top of previously sintered layers by a single-line laser scanning is presented. A temperature-transforming model is employed to model melting and resolidification accompanied by partial shrinkage during laser sintering. The heat losses at the top surface due to natural convection and radiation are taken into account. The liquid flow of the molten low-melting-point metal powders, which is driven by capillary and gravity forces, is also considered and formulated by using Darcy’s law. The effects of the dominant processing parameters, such as laser-beam intensity, scanning velocity, and number of the existing sintered layers underneath, are investigated.

Analysis of Melting in a Single-Component Metal Powder Bed Subject to Constant Heat Flux Heating

Volume 3 ◽  
2004 ◽  
Author(s):  
Bin Xiao ◽  
Yuwen Zhang
Keyword(s):  
Heat Flux ◽  
Melting Point ◽  
Metal Powder ◽  
Solid Phase ◽  
Selective Laser Sintering ◽  
Single Component ◽  
Density Change ◽  
Dimensional System ◽  
Metal Powders ◽  
Powder Bed

To model Selective Laser Sintering (SLS) of single-component metal powders, melting of a subcooled powder bed with single-component metal powder is investigated analytically. Since laser processing of metal powder is a very rapid process, the liquid and solid phases of a partially molten powder particle may have different temperatures: the temperature in the liquid phase is higher than the melting point, and the temperature in the solid phase is below the melting point. Therefore, the local temperature of regions with partial molten particles is within a range of temperature adjacent to the melting point, instead of at melting point. In addition, the powder bed experiences a significant density change during melting. Therefore, melting of a metal powder bed can be modeled as a melting that occurs in a range of temperature with significant density change. The temperature distributions and locations of the various interfaces were obtained by solving the governing equations for solid, liquid and mushy zones in a one-dimensional system using an integral approximate method. The effects of porosity, sub-cooling, dimensionless thermal conductivity of gas, and dimensionless heat flux on the surface temperature and locations of the interfaces were investigated.

Three-Dimensional Simulation of Multiple-Line Laser Sintering of a Two-Component Metal Powder Layer on Top of Sintered Layers

2005 ◽  
Author(s):  
Tiebing Chen ◽  
Yuwen Zhang
Keyword(s):  
Laser Beam ◽  
Metal Powder ◽  
Scanning Speed ◽  
Processing Parameters ◽  
Powder Layer ◽  
Metal Powders ◽  
Gaussian Laser Beam ◽  
Laser Beam Intensity ◽  
Multiple Line ◽  
Two Component

Multiple line laser scan sintering of a two-component metal powder layer on top of the sintered layers with a moving circular Gaussian laser beam is modeled numerically. The overlap between the adjacent scan lines to achieve enhanced bonding is taken into account. The binding between the newly sintered layer and existing sintered layers underneath through melting is also considered. The governing equation is formulated by a temperature-transforming model with partial shrinkage induced by melting considered. The liquid flow of the molten low melting point metal powders, which is driven by capillary and gravity forces, is formulated by Darcy’s law. The effects of the dominant processing parameters, including the moving laser beam intensity, scanning speed and number of the existing sintered layers underneath, on the shape of the heat affected zone (HAZ) are investigated. A parametric study is performed and the best combination of the processing parameters is recommended.

Three-Dimensional Modeling of Selective Laser Sintering of Two-Component Metal Powder Layers

2005 ◽  
Vol 128 (1) ◽  
pp. 299-306 ◽  
Author(s):  
Tiebing Chen ◽  
Yuwen Zhang
Keyword(s):  
Metal Powder ◽  
Continuous Wave ◽  
Selective Laser Sintering ◽  
Three Dimensional ◽  
Laser Sintering ◽  
Powder Layer ◽  
Metal Powders ◽  
Gaussian Laser Beam ◽  
Scanning Velocity ◽  
Three Dimensional Modeling

Laser sintering of a metal powder mixture that contains two kinds of metal powders with significantly different melting points under a moving Gaussian laser beam is investigated numerically. The continuous-wave laser-induced melting accompanied by shrinkage and resolidification of the metal powder layer are modeled using a temperature-transforming model. The liquid flow of the melted low-melting-point metal driven by capillary and gravity forces is also included in the physical model. The numerical results are validated by experimental results, and a detailed parametric study is performed. The effects of the moving heat source intensity, the scanning velocity, and the thickness of the powder layer on the sintering depth, the configuration of the heat affected zone, and the temperature distribution are discussed.

Analysis and modeling of direct selective laser sintering of two-component metal powders

2005 ◽  
Author(s):  
◽  
Tiebing Chen
Keyword(s):  
Laser Beam ◽  
Selective Laser Sintering ◽  
Finite Thickness ◽  
Three Dimensional ◽  
Laser Sintering ◽  
Powder Layer ◽  
Metal Powders ◽  
Gaussian Laser Beam ◽  
Scanning Velocity ◽  
Two Component

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Direct Selective Laser Sintering (SLS) is an emerging technology of Solid Freeform Fabrication (SFF) that 3-D parts are built from the metal-based powder bed with CAD data. A one-dimensional analytical model of melting in a two-component powder layer with finite thickness subjected to a constant heat flux heating and a two-dimensional numerical model of SLS of a two-component powder layer with a moving laser beam scanning were developed consecutively. Three-dimensional modeling of laser sintering of a two-component metal powder mixture under a moving Gaussian laser beam was investigated numerically at last. The effects of the moving heat source intensity, the scanning velocity, the thickness of the powder layer and the number of existing sintered layers underneath on the sintering depth, the configuration of the heat affected zone (HAZ) and the temperature distribution are discussed.

Structure forming of Cu–W pseudoalloys prepared in different routes

2021 ◽  
pp. 12-20
Author(s):  
S. G. Vadchenko ◽  
E. V. Suvorova ◽  
N. I. Mukhina ◽  
I. D. Kovalev ◽  
E. V. Illarionova
Keyword(s):  
Melting Point ◽  
Mechanical Activation ◽  
Metal Powder ◽  
Tungsten Powder ◽  
Copper Deposition ◽  
Composite Particles ◽  
Average Particle ◽  
Metal Powders ◽  
Composite Powders ◽  
Powder Mixtures

The microstructures of alloys formed during the sintering of tungsten powder mixtures (PV2, 3.8–6.0 μm average particle size) and copper (PMS-11, 45–60 μm fraction) prepared by various methods were compared. The methods included simple metal powder mixing, mechanical activation (MA) of metal powders, copper precipitation from the solution of its sulfate (CuSO4·5H2O) on tungsten powder with simultaneous mechanical activation. The molar ratio of metals in mixtures Cu/W = 1. An aqueous solution for copper deposition included diethylene glycol (up to 30 %), glycerin (up to 8 %), hydrofluoric acid (up to 0.1 %), wetting agent OP-10 (up to 0.8 %). Mechanical activation was carried out in an AGO-2 planetary mill with 200 g of steel balls charged into the drums rotating at 2220 rpm for 5 min. Reduced copper in the solution and in the air rapidly oxidizes to the Cu2O oxide, so the composite powders obtained were washed, dried, and stored in an argon atmosphere. Samples pressed from the powders obtained (tablets 3 mm in diameter, 1.5–2.0 mm in height with a density of 7.7–8.0 g/cm3) were sintered in argon at atmospheric pressure and temperatures from 1000 to 1500 °C. During the sintering of Cu–W composite particles, several areas of the process can be distinguished. «Solid phase» sintering occurs at the contact points of composite particles at temperatures lower than the copper melting point. When samples are heated from the melting point to 1200 °C, samples are sintered by the liquid-phase mechanism from the conventional mixture of metal powders to form a low-porous cake. When composite powders obtained by MA during the copper deposition and MA of metal powder mixtures are sintered, samples are delaminated with the formation of large pores elongated perpendicular to the pressing axis and partially filled with copper melt. When samples obtained by powder MA are heated above 1400 °C, phase separation occurs and almost all copper is displaced from the sample to the surface.

Melting and Resolidification of a Two-Component Metal Powder Layer Heated by a Moving Gaussian Heat Source

2003 ◽  
Author(s):  
Tiebing Chen ◽  
Yuwen Zhang
Keyword(s):  
Steady State ◽  
Heat Source ◽  
Coordinate System ◽  
Metal Powder ◽  
Powder Layer ◽  
Moving Heat Source ◽  
Metal Powders ◽  
Melting Points ◽  
Scanning Velocity ◽  
Two Component

Melting and resolidification of a subcooled mixed metal powder layer that contains a mixture of two metal powders with significantly different melting points heated by a moving Gaussian heat source is investigated numerically. The phase change is modeled using a temperature-transforming model and shrinkage induced by melting is also taken into account. The problem appears to be steady-state since it is formulated in a coordinate system moving with the Gaussian heat source and the size of the powder is much larger than that of the heat source. The results show that the powder layer thickness, moving heat source intensity and scanning velocity have significant effects on the sintering depth.

scholarly journals Carbon Particle In-Situ Alloying of the Case-Hardening Steel 16MnCr5 in Laser Powder Bed Fusion

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 896
Author(s):  
Matthias Schmitt ◽  
Albin Gottwalt ◽  
Jakob Winkler ◽  
Thomas Tobie ◽  
Georg Schlick ◽  
...  
Keyword(s):  
Laser Beam ◽  
Mechanical Strength ◽  
Carbon Content ◽  
Metal Powder ◽  
Case Hardening ◽  
Powder Bed Fusion ◽  
Powder Bed ◽  
Carbon Particles ◽  
Case Hardening Steel

The carbon content of steel affects many of its essential properties, e.g., hardness and mechanical strength. In the powder bed fusion process of metals using a laser beam (PBF-LB/M), usually, pre-alloyed metal powder is solidified layer-by-layer using a laser beam to create parts. A reduction of the carbon content in steels is observed during this process. This study examines adding carbon particles to the metal powder and in situ alloying in the PBF-LB/M process as a countermeasure. Suitable carbon particles are selected and their effect on the particle size distribution and homogeneity of the mixtures is analysed. The workability in PBF-LB is then shown. This is followed by an evaluation of the resulting mechanical properties (hardness and mechanical strength) and microstructure in the as-built state and the state after heat treatment. Furthermore, potential use cases like multi-material or functionally graded parts are discussed.

Development of low-melting-point filler materials for laser beam brazing of aluminum alloys

2014 ◽  
Vol 45 (8) ◽  
pp. 717-726 ◽  
Author(s):  
C. Cui ◽  
A. Schulz ◽  
L. Achelis ◽  
V. Uhlenwinkel ◽  
H. Leopold ◽  
...  
Keyword(s):  
Melting Point ◽  
Aluminum Alloys ◽  
Laser Beam ◽  
Filler Materials

scholarly journals Combustion Synthesis of Aluminum Oxynitride in Loose Powder Beds

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4182
Author(s):  
Alan Wilmański ◽  
Magdalena Zarzecka-Napierała ◽  
Zbigniew Pędzich
Keyword(s):  
Combustion Synthesis ◽  
Metal Powder ◽  
Weight Ratio ◽  
Nitrogen Pressure ◽  
Alumina Powder ◽  
Metal Powders ◽  
Aluminum Oxynitride ◽  
Synthesis Conditions ◽  
Aluminum Metal ◽  
Loose Powder

This paper describes combusting loose powder beds of mixtures of aluminum metal powders and aluminum oxide powders with various grain sizes under various nitrogen pressure. The synthesis conditions required at least 20/80 weight ratio of aluminum metal powder to alumina powder in the mix to reach approximately 80 wt% of γ-AlON in the products. Finely ground fused white alumina with a mean grain size of 5 μm was sufficient to achieve results similar to very fine alumina with 0.3 μm grains. A lower nitrogen pressure of 1 MPa provided good results, allowing a less robust apparatus to be used. The salt-assisted combustion synthesis upon addition of 10 wt% of ammonium nitrite resulted in a slight increase in product yield and allowed lower aluminum metal powder content in mixes to be ignited. Increasing the charge mass five times resulted in a very similar γ-AlON yield, providing a promising technology for scaling up. Synthesis in loose powder beds could be utilized for effective production of relatively cheap and uniform AlON powder, which could be easily prepared for forming and sintering without intensive grounding and milling, which usually introduce serious contamination.

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