Microstructure Evolution During Solid-State Selective Laser Sintering of Metallic Materials: A Phase-Field Simulation

2019 ◽  
Author(s):  
Xing Zhang ◽  
Yiliang Liao
Keyword(s):  
Solid State ◽  
Microstructure Evolution ◽  
Phase Field ◽  
Laser Power ◽  
Laser Scanning ◽  
Large Scale ◽  
Selective Laser Sintering ◽  
High Energy ◽  
Laser Sintering ◽  
Scanning Velocity

Abstract Selective laser sintering/melting (SLS/SLM) is a rapid prototyping technique that utilizes a high-energy laser beam to bind powder particles together for solid part fabrication. Due to the presence of several factors, microstructure-based material modeling can be of significant importance for optimizing processing parameters. To date, most researchers have put their efforts on simulating the microstructure of SLM-processed component, while few attentions have been paid to investigate the evolving of microstructure during SLS. In this work, a phase-field model is proposed to simulate the microstructure evolution during the solid-state SLS process. The microstructure evolution as affected by the laser power and scanning velocity are studied. It is found that the width of sintering neck increases with the increase of laser power and the decrease of laser scanning velocity. The modeling predictions are compared with the experimental data regarding the neck width between adjacent particles. In addition, it is demonstrated that this model is capable of carrying out large-scale simulations.

Direct Selective Laser Sintering of WC-Co Cemented Carbide by Premixing of Additives

2012 ◽  
Author(s):  
Hideki Kyogoku ◽  
Takeshi Uemori ◽  
Akihiko Ikuta ◽  
Kenichi Yoshikawa ◽  
Hitoshi Ohmori
Keyword(s):  
Selective Laser Melting ◽  
Laser Power ◽  
Smooth Surface ◽  
Laser Scanning ◽  
Selective Laser Sintering ◽  
Laser Sintering ◽  
Cemented Carbides ◽  
Sintering Process ◽  
Laser Melting ◽  
Scan Speed

In this study, the fabrication conditions of WC cemented carbides by direct selective laser melting were investigated. The effects of additives, such as Co, Cu-20%Sn and Cu powders, and laser scanning conditions on laser sintering process were examined to fabricate a sound laser-scanned body of WC cemented carbides. The optimum laser power, scan speed and scan pitch were found out by experiments. It was found that the continuously smooth single-scan track can be obtained at a lower laser power and a higher scan speed by the addition of 30% Cu powder. The smooth surface of the laser-scanned body could be fabricated at a laser power of 9 W, a scan speed of 20 mm/s and a scan pitch of 0.05 mm.

Solid-State Transformation Produced by Laser Treatment and Mechanical Alloying of Fe-Ni-Cu(P) Powders

2008 ◽  
Vol 589 ◽  
pp. 391-396
Author(s):  
Szabolcs Herczeg ◽  
János Takács ◽  
Ágnes Csanády ◽  
Gyula Kakuk ◽  
Jenő Sólyom ◽  
...  
Keyword(s):  
Solid State ◽  
Mechanical Alloying ◽  
Laser Scanning ◽  
Scanning Speed ◽  
High Energy ◽  
Laser Sintering ◽  
Solid State Reactions ◽  
State Transformation ◽  
Solid State Transformation ◽  
Laser Scanning Speed

The comparison of the phase transformations going on due to high energy ball milling (HEBM) and produced by pressure-less Direct Metal Laser Sintering (DMLS developed by EOS company) was carried out, by using an α-Fe, Ni and Cu3P powder mixture. It could be shown by X-ray diffractograms (XRD) of the two type of products, that by mechanical alloying a similar phase transformation occurs due to solid state reactions between the metal partners as in the case of laser sintering, in a given range of laser scanning speed in a laboratory laser equipment. According to the XRD evaluation the same metastable, γ-steel like phases were formed.

scholarly journals Fabrication of porous bioactive structures using the selective laser sintering technique

2007 ◽  
Vol 221 (8) ◽  
pp. 873-886 ◽  
Author(s):  
M M Savalani ◽  
L Hao ◽  
Y Zhang ◽  
K E Tanner ◽  
R A Harris
Keyword(s):  
Laser Power ◽  
Laser Scanning ◽  
Selective Laser Sintering ◽  
Negative Relationship ◽  
Vertical Plane ◽  
Laser Sintering ◽  
Custom Made ◽  
The Matrix ◽  
Scan Speed ◽  
Liquid Displacement

Hydroxyapatite, a ceramic with which natural bone inherently bonds, has been incorporated into a polymer matrix to enhance the bioactivity of implant materials. In order to manufacture custom-made bioactive implants rapidly, selective laser sintering has been investigated to fabricate hydroxyapatite and polyamide composites and their properties investigated. One objective of this research was to identify the maximum hydroxyapatite content that could be incorporated into the matrix, which was sintered at various parameters. The study focused on investigating the control of porosity and pore size of the matrix by manipulating the selective laser sintering parameters of the laser power and laser scan speed. The interception method was used to analyse the internal porous morphology of the matrices which were cross-sectioned through the vertical plane. Most notably, all structures built demonstrated interconnection and penetration throughout the matrix. Liquid displacement was also used to analyse the porosity of the matrices. The laser power showed a negative relationship between porosity and variation in parameter values until a critical power value was reached. However, the same relationship for laser scan speed matrices was inconsistent. The effects of the laser power and laser scanning speed on the features of porous structures that could influence cell spreading, proliferation, and bone regeneration are presented.

Study in performance and morphology of polyamide 12 produced by selective laser sintering technology

2018 ◽  
Vol 24 (5) ◽  
pp. 813-820 ◽  
Author(s):  
Junjie Wu ◽  
Xiang Xu ◽  
Zhihao Zhao ◽  
Minjie Wang ◽  
Jie Zhang
Keyword(s):  
Selective Laser Sintering ◽  
Polarized Light ◽  
Chain Scission ◽  
High Energy ◽  
Laser Sintering ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Content Type ◽  
X Ray ◽  
Polyamide 12

Purpose The purpose of this paper is to investigate the effect of selective laser sintering (SLS) method on morphology and performance of polyamide 12. Design/methodology/approach Crystallization behavior is critical to the properties of semi-crystalline polymers. The crystallization condition of SLS process is much different from others. The morphology of polyamide 12 produced by SLS technology was investigated using scanning electron microscopy, polarized light microscopy, differential scanning calorimetry, X-ray diffraction and wide-angle X-ray diffraction. Findings Too low fill laser power brought about bad fusion of powders, while too high energy input resulted in bad performance due to chain scission of macromolecules. There were three types of crystal in the raw powder material, denoted as overgrowth crystal, ring-banded spherulite and normal spherulite. Originality/value In this work, SLS samples with different sintering parameters, as well as compression molding sample for the purpose of comparison, were made to study the morphology and crystal structure of sintered PA12 in detail.

Research on Warpage of Polystyrene in Selective Laser Sintering

2010 ◽  
Vol 43 ◽  
pp. 578-582 ◽  
Author(s):  
C.Y. Wang ◽  
Q. Dong ◽  
X.X. Shen
Keyword(s):  
Layer Thickness ◽  
Process Parameters ◽  
Laser Power ◽  
Selective Laser Sintering ◽  
Scanning Speed ◽  
Laser Sintering ◽  
Main Process ◽  
Influence Of Process Parameters ◽  
Temperature Changes ◽  
Hatch Spacing

Warpage is a crucial factor to accuracy of sintering part in selective laser sintering (SLS) process. In this paper, The influence of process parameters on warpage when sintering polystyrene(PS) materials in SLS are investigated. The laser power, scanning speed, hatch spacing, layer thickness as well as temperature of powder are considered as the main process parameters. The results showed that warpage increases with the increase of hatch space. Contary to it, warpage decreases with the increase of laser power. Warpage decreases with the increase of layer thickness between 0.16~0.18mm and changes little with increase of the thickness. Warpage increases along with the increase of scanning speed but decreases when the speed is over about 2000mm/s. When the temperature changes between 82°C-86°C, warpage decreases little with the increase of temperature. But further increase of temperature leads to warpage decreasing sharply when the temperature changes between 86°C-90°C.

Formability of the Layer Additive Ceramic Part

2008 ◽  
Vol 594 ◽  
pp. 241-248 ◽  
Author(s):  
Fwu Hsing Liu ◽  
Yunn Shiuan Liao ◽  
Hsiu Ping Wang
Keyword(s):  
Surface Roughness ◽  
Laser Scanning ◽  
Selective Laser Sintering ◽  
Single Layer ◽  
Dimensional Accuracy ◽  
Scanning Speed ◽  
Laser Sintering ◽  
Single Line ◽  
Laser Scanning Speed ◽  
Silica Slurry

The material in powder state has long been used by selective laser sintering (SLS) for making rapid prototyping (RP) parts. A new approach to fabricate smoother surface roughness RP parts of ceramic material from slurry-sate has been developed in this study. The silica slurry was successfully laser-gelling in a self-developed laser sintering equipment. In order to overcome the insufficient bonding strength between layers, a strategy is proposed to generate ceramic parts from a single line, a single layer, to multi-layers of gelled cramic in this paper. It is found that when the overlap of each single line is 25% and the over-gel between layers is 30%, stronger and more accurate dimensional parts can be obtained under a laser power of 15W, a laser scanning speed of 250 mm/s, and a layer thickness of 0.1 mm. The 55:45 wt. % of the proportion between the silica powder and silica solution results in suitable viscosity of the ceramic slurries without precipitation. Furthermore, the effects of process parameters for the dimensional accuracy and surface roughness of the gelled parts are investigated and appropriate parameters are obtained.

Physical Modeling for Selective Laser Sintering Process

2017 ◽  
Vol 17 (2) ◽  
Author(s):  
Arash Gobal ◽  
Bahram Ravani
Keyword(s):  
Physical Modeling ◽  
Large Scale ◽  
Selective Laser Sintering ◽  
Powdered Material ◽  
Laser Sintering ◽  
Industrial Applications ◽  
Transient Temperature ◽  
Sintering Process ◽  
Powder Bed ◽  
Selective Heating

The process of selective laser sintering (SLS) involves selective heating and fusion of powdered material using a moving laser beam. Because of its complicated manufacturing process, physical modeling of the transformation from powder to final product in the SLS process is currently a challenge. Existing simulations of transient temperatures during this process are performed either using finite-element (FE) or discrete-element (DE) methods which are either inaccurate in representing the heat-affected zone (HAZ) or computationally expensive to be practical in large-scale industrial applications. In this work, a new computational model for physical modeling of the transient temperature of the powder bed during the SLS process is developed that combines the FE and the DE methods and accounts for the dynamic changes of particle contact areas in the HAZ. The results show significant improvements in computational efficiency over traditional DE simulations while maintaining the same level of accuracy.

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