Texture control of 316L parts by modulation of the melt pool morphology in selective laser melting

Various selective laser melting (SLM) configurations (8 in all) were tested on aluminum alloy AlSi7Mg0.6 by making single tracks on parallelepipeds specimens. We used an energy balance as a means of connecting the machine parameters (power, speed, etc.) of the 8 configurations to the morphology (geometry) of the single tracks. On this basis, we correlated the width, depth and especially the section area of the melt pool (single track) to the linear energy density. We were also able to assess the absorption coefficient of the aluminum alloy AlSi7Mg0.6 as a function of the temperature. The study was then focused on the microstructure and the possible impacts on the material properties including on the mechanical characteristics and the anisotropy observed in literature based on the build direction. Evidence suggests that the Hall-Petch relation can be used to explain this anisotropy. The thermal analysis highlighted two laser operating modes: the keyhole mode and the conduction mode. These modes have also been described via the morphology of the single tracks. Finally, a comparison between Rosenthal’s theoretical model (in the case of the conduction mode) and actual conditions was proposed by the obtained geometry of the single tracks as well as the cooling speeds calculated and measured using the dendrite arm spacing (DAS). The maximum temperatures achieved were also assessed by Rosenthal’s theoretical model which made it possible to explain the evaporation of some chemical elements during the manufacturing of the aluminum alloy through SLM.

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Study and modeling of melt pool evolution in selective laser melting process of SS316L

MRS Communications ◽

10.1557/mrc.2018.180 ◽

2018 ◽

Vol 8 (03) ◽

pp. 1178-1183 ◽

Cited By ~ 2

Author(s):

J. L. Tan ◽

C. Tang ◽

C. H. Wong

Keyword(s):

Selective Laser Melting ◽

Melting Process ◽

Laser Melting ◽

Selective Laser Melting Process ◽

Melt Pool ◽

Image Position

Abstract

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An Overview of Additive Manufacturing Technologies—A Review to Technical Synthesis in Numerical Study of Selective Laser Melting

Materials ◽

10.3390/ma13173895 ◽

2020 ◽

Vol 13 (17) ◽

pp. 3895 ◽

Cited By ~ 2

Author(s):

Abbas Razavykia ◽

Eugenio Brusa ◽

Cristiana Delprete ◽

Reza Yavari

Keyword(s):

Numerical Simulation ◽

Additive Manufacturing ◽

Selective Laser Melting ◽

Powder Bed Fusion ◽

Laser Melting ◽

Powder Bed ◽

Part Quality ◽

Melt Pool ◽

Wide Range ◽

Am Processes

Additive Manufacturing (AM) processes enable their deployment in broad applications from aerospace to art, design, and architecture. Part quality and performance are the main concerns during AM processes execution that the achievement of adequate characteristics can be guaranteed, considering a wide range of influencing factors, such as process parameters, material, environment, measurement, and operators training. Investigating the effects of not only the influential AM processes variables but also their interactions and coupled impacts are essential to process optimization which requires huge efforts to be made. Therefore, numerical simulation can be an effective tool that facilities the evaluation of the AM processes principles. Selective Laser Melting (SLM) is a widespread Powder Bed Fusion (PBF) AM process that due to its superior advantages, such as capability to print complex and highly customized components, which leads to an increasing attention paid by industries and academia. Temperature distribution and melt pool dynamics have paramount importance to be well simulated and correlated by part quality in terms of surface finish, induced residual stress and microstructure evolution during SLM. Summarizing numerical simulations of SLM in this survey is pointed out as one important research perspective as well as exploring the contribution of adopted approaches and practices. This review survey has been organized to give an overview of AM processes such as extrusion, photopolymerization, material jetting, laminated object manufacturing, and powder bed fusion. And in particular is targeted to discuss the conducted numerical simulation of SLM to illustrate a uniform picture of existing nonproprietary approaches to predict the heat transfer, melt pool behavior, microstructure and residual stresses analysis.

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Thermo-Fluid-Dynamic Modeling of the Melt Pool during Selective Laser Melting for AZ91D Magnesium Alloy

Materials ◽

10.3390/ma13184157 ◽

2020 ◽

Vol 13 (18) ◽

pp. 4157

Author(s):

Hongyao Shen ◽

Jinwen Yan ◽

Xiaomiao Niu

Keyword(s):

Temperature Distribution ◽

Magnesium Alloy ◽

Selective Laser Melting ◽

Laser Power ◽

Large Temperature ◽

Fe Model ◽

Laser Melting ◽

Az91d Magnesium Alloy ◽

Melt Pool ◽

Flow Activity

A three dimensional finite element model (FEM) was established to simulate the temperature distribution, flow activity, and deformation of the melt pool of selective laser melting (SLM) AZ91D magnesium alloy powder. The latent heat in phase transition, Marangoni effect, and the movement of laser beam power with a Gaussian energy distribution were taken into account. The influence of the applied linear laser power on temperature distribution, flow field, and the melt-pool dimensions and shape, as well as resultant densification activity, was investigated and is discussed in this paper. Large temperature gradients and high cooling rates were observed during the process. A violent flow occurred in the melt pool, and the divergent flow makes the melt pool wider and longer but shallower. With the increase of laser power, the melt pool’s size increases, but the shape becomes longer and narrower. The width of the melt pool in single-scan experiment is acquired, which is in good agreement with the results predicted by the simulation (with error of 1.49%). This FE model provides an intuitive understanding of the complex physical phenomena that occur during SLM process of AZ91D magnesium alloy. It can help to select the optimal parameters to improve the quality of final parts and reduce the cost of experimental research.

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A Comparative Study Between Selective Laser Melting and Electron Beam Additive Manufacturing Based on Thermal Modeling

Volume 1: Advances in Aerospace Technology ◽

10.1115/imece2018-86428 ◽

2018 ◽

Cited By ~ 1

Author(s):

M. Shafiqur Rahman ◽

Paul J. Schilling ◽

Paul D. Herrington ◽

Uttam K. Chakravarty

Keyword(s):

Electron Beam ◽

Additive Manufacturing ◽

Heat Source ◽

Selective Laser Melting ◽

Thermal Modeling ◽

Maximum Temperature ◽

Full Density ◽

Rate Variation ◽

Laser Melting ◽

Melt Pool

Selective Laser Melting (SLM) and Electron Beam Additive Manufacturing (EBAM) are two of the most promising additive manufacturing technologies that can make full density metallic components using layer-by-layer fabrication methods. In this study, three-dimensional computational fluid dynamics models with Ti-6Al-4V powder were developed to conduct numerical simulations of both the SLM and EBAM processes. A moving conical volumetric heat source with Gaussian distribution and temperature-dependent thermal properties were incorporated in the thermal modeling of both processes. The melt-pool geometry and its thermal behavior were investigated numerically and results for temperature profile, cooling rate, variation in specific heat, density, thermal conductivity, and enthalpy were obtained with similar heat source specifications. Results obtained from the two models at the same maximum temperature of the melt pool were then compared to describe their deterministic features to be considered for industrial applications. Validation of the modeling was performed by comparing the EBAM simulation results with the EBAM experimental results for melt pool geometry.

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Layer-wise control of selective laser melting by means of inline melt pool area measurements

Journal of Laser Applications ◽

10.2351/7.0000108 ◽

2020 ◽

Vol 32 (2) ◽

pp. 022057

Author(s):

Ema Vasileska ◽

Ali Gökhan Demir ◽

Bianca Maria Colosimo ◽

Barbara Previtali

Keyword(s):

Selective Laser Melting ◽

Laser Melting ◽

Melt Pool ◽

Pool Area

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Phase Change with Density Variation and Cylindrical Symmetry: Application to Selective Laser Melting

Journal of Manufacturing and Materials Processing ◽

10.3390/jmmp3030062 ◽

2019 ◽

Vol 3 (3) ◽

pp. 62 ◽

Cited By ~ 1

Author(s):

Fyrillas ◽

Ioannou ◽

Papadakis ◽

Rebholz ◽

Doumanidis

Keyword(s):

Heat Transfer ◽

Heat Source ◽

Phase Change ◽

Selective Laser Melting ◽

Unit Length ◽

Cylindrical Symmetry ◽

Density Variation ◽

Laser Melting ◽

Molten Material ◽

Melt Pool

In this paper we introduce an analytical approach for predicting the melting radius during powder melting in selective laser melting (SLM) with minimum computation duration. The purpose of this work is to evaluate the suggested analytical expression in determining the melt pool geometry for SLM processes, by considering heat transfer and phase change effects with density variation and cylindrical symmetry. This allows for rendering first findings of the melt pool numerical prediction during SLM using a quasi-real-time calculation, which will contribute significantly in the process design and control, especially when applying novel powders. We consider the heat transfer problem associated with a heat source of power Q' (W/m) per unit length, activated along the span of a semi-infinite fusible material. As soon as the line heat source is activated, melting commences along the line of the heat source and propagates cylindrically outwards. The temperature field is also cylindrically symmetric. At small times (i.e., neglecting gravity and Marangoni effects), when the density of the solid material is less than that of the molten material (i.e., in the case of metallic powders), an annulus is created of which the outer interface separates the molten material from the solid. In this work we include the effect of convection on the melting process, which is shown to be relatively important. We also justify that the assumption of constant but different properties between the two material phases (liquid and solid) does not introduce significant errors in the calculations. A more important result; however, is that, if we assume constant energy input per unit length, there is an optimum power of the heat source that would result to a maximum amount of molten material when the heat source is deactivated. The model described above can be suitably applied in the case of selective laser melting (SLM) when one considers the heat energy transferred to the metallic powder bed during scanning. Using a characteristic time and length for the process, we can model the energy transfer by the laser as a heat source per unit length. The model was applied in a set of five experimental data, and it was demonstrated that it has the potential to quantitatively describe the SLM process.

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