Simulation Informed Effects of Solidification Rate on 316L Single Tracks Produced by Selective Laser Melting

2020 ◽  
Author(s):  
A. L. K. Rawlings ◽  
A. J. Birnbaum ◽  
J. G. Michopoulos ◽  
J. C. Steuben ◽  
A. P. Iliopoulos ◽  
...  
Keyword(s):  
Selective Laser Melting ◽  
Process Parameters ◽  
Solidification Rate ◽  
Interface Velocity ◽  
Processing Parameters ◽  
Spot Size ◽  
Grain Structure ◽  
Material System ◽  
Laser Melting ◽  
Specific Material

Abstract The formation of sub-grain cellular structures generated during the rapid solidification associated with selective laser melting (SLM) typically yields enhanced mechanical properties in terms of yield stress without considerable loss in ductility when compared with those of wrought material. The extent to which the sub-grain structure appears under standard metallographic preparation shows dependence on multiple systematic conditions. This study identifies the effects of solidification and cooling rate on the grain and sub-grain structure in stainless steel through varying the processing parameters (laser power, scan velocity and spot size) of single tracks on both as-received, small grain and annealed, giant grain substrates. The process parameters, in conjunction with the initial substrate microstructure, are key components in understanding the resulting microstructure. Process parameters, particularly scan velocity, dictate the solidification rate and primary regrowth directions while the initial microstructure and its thermomechanical history dictate the propensity for stored strain energy density. Modeling the thermal process allows for experimental analysis within the context of predicted location within processing space as it pertains to local interface velocity and temperature gradient. Furthermore, it highlights the fact that this specific material system behaves in a manner that is inconsistent with classical solidification theory.

Parameter optimization of aluminum alloy thin structures obtained by Selective Laser Melting

MRS Advances ◽  
2019 ◽  
Vol 4 (55-56) ◽  
pp. 2997-3005
Author(s):  
Malena Ley Bun Leal ◽  
Barbara Bermudez-Reyes ◽  
Patricia del Carmen Zambrano Robledo ◽  
Omar Lopez-Botello
Keyword(s):  
Selective Laser Melting ◽  
Process Parameters ◽  
Orthogonal Design ◽  
Processing Parameters ◽  
Future Research ◽  
Laser Melting ◽  
Complex Process ◽  
The Relationship ◽  
Fabrication Parameters

ABSTRACTSelective Laser Melting (SLM) involves numerous fabrication parameters, the interaction between those parameters determine the final characteristics of the resulting part and because of the latter, it is considered a complex process. Low-density components is one of the main issues of the SLM process, due to the incorrect selection of process parameters. These defects are undesired in high specialized applications (i.e. aerospace, aeronautic and medical industries). Therefore, the characterization of the defects (pores) found in aluminum parts manufacture by SLM and the relationship with fabrication parameters was performed. A robust orthogonal design of experiments was implemented to determine process parameters, and then parts were manufactured in SLM. Relative density of the samples was then characterized using the Archimedes principle and microscopy; the data was then statistically analyzed in order to determine the optimal process parameters. The main purpose of the present research was to establish the best processing parameters of an in-house SLM system, as well as to characterize the pore geometry in order to fully eliminate pores in a future research.

scholarly journals Formation of SS316L Single Tracks in Micro Selective Laser Melting: Surface, Geometry, and Defects

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Zhiheng Hu ◽  
Balasubramanian Nagarajan ◽  
Xu Song ◽  
Rui Huang ◽  
Wei Zhai ◽  
...  
Keyword(s):  
Selective Laser Melting ◽  
Process Parameters ◽  
Molten Pool ◽  
Fine Powder ◽  
Spot Size ◽  
Powder Size ◽  
Surface Geometry ◽  
Laser Melting ◽  
Scanning Velocity ◽  
Melting Surface

To fabricate complex parts with a fine resolution and smooth finish, micro selective laser melting (SLM) has been developed recently by combining three attributes: small laser beam spot, fine powder size, and thin layer thickness. This paper studies the effect of the micro-SLM process parameters on the single track formation of 316L stainless steel. The surface morphology, geometrical features, and defects have been analyzed in detail. The results highlight that laser power and scanning velocity have a significant effect on the formation of single tracks. The single tracks fabricated through micro-SLM with varying process parameters are classified into four types: no melting, discontinuous, continuous but unstable, and continuous tracks. Besides, the top surface of the tracks is observed with “double-crest” morphology, due to the high recoil pressure gradient generated by the extremely fine spot size. In addition, molten pool geometry (width, depth, and height) has been characterized to study the mode of the molten pool in micro-SLM. Finally, the occurrence of two typical defects within the tracks, keyhole pore and cavity at the edges, has been studied.

scholarly journals 3D Multi-Track and Multi-Layer Epitaxy Grain Growth Simulations of Selective Laser Melting

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7346
Author(s):  
Amir Reza Ansari Dezfoli ◽  
Yu-Lung Lo ◽  
M. Mohsin Raza
Keyword(s):  
Cooling Rate ◽  
Grain Growth ◽  
Selective Laser Melting ◽  
Laser Scanning ◽  
Processing Parameters ◽  
Grain Structure ◽  
Laser Melting ◽  
Scanning Strategy ◽  
Integrated Simulation ◽  
3D Finite Element Method

An integrated simulation framework consisting of the 3D finite element method and 3D cellular automaton method is presented for simulating the multi-track and multi-layer selective laser melting (SLM) process. The framework takes account of all the major multi-physics phenomena in the SLM process, including the initial grain structure, the growth kinetics, the laser scanning strategy, the laser–powder and laser–matter interactions, the melt flow, and the powder-to-liquid-to-solid transformations. The feasibility of the proposed framework is demonstrated by simulating the evolution of the epitaxy grain structure of Inconel 718 (IN718) during a 15-layer SLM process performed using a bi-directional 67° rotation scanning strategy and various SLM process parameters. The simulation results are found to be in good agreement with the experimental observations obtained in the present study and in the literature. In particular, a strong (001) texture is observed in the final component, which indicates that the grains with a preferred <001> orientation win the competitive epitaxy grain growth process. In addition, the size and shape of the IN718 grains are governed primarily by the cooling rate, where the cooling rate is determined in turn by the SLM parameters and the build height. Overall, the results show that the proposed framework provides an accurate approach for predicting the final microstructures of SLM components, and therefore, it can play an important role in optimizing the SLM processing parameters in such a way as to produce components with the desired mechanical properties.

Microstructural and Mechanical Properties of Selective Laser Melted Al 4047

2015 ◽  
Vol 752-753 ◽  
pp. 485-490 ◽  
Author(s):  
Shafaqat Siddique ◽  
Eric Wycisk ◽  
Gerrit Frieling ◽  
Claus Emmelmann ◽  
Frank Walther
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Selective Laser Melting ◽  
Process Parameters ◽  
Processing Parameters ◽  
Complex Geometries ◽  
Optimal Parameters ◽  
Post Processing ◽  
Laser Melting ◽  
Process Cost

Selective laser melting (SLM) has been recognized as a pertinent process for manufacturing of complex geometries. Al 4047 has been manufactured in this study with different processing parameters of the SLM process to obtain the optimal parameters suitable for required applications, as well as to determine the effect of these parameters and post-processing heat treatment on mechanical properties. A unique Al-Si eutectic microstructure is obtained with Al dendrites growing in the scanning direction. Mechanical properties of the SLM manufactured Al 4047 are at par with those of conventionally manufactured alloy. These properties can be varied by changing the SLM process parameters which can help controlling the process cost depending upon required mechanical properties.

scholarly journals High Bending Strength Hypereutectic Al-22Si-0.2Fe-0.1Cu-Re Alloy Fabricated by Selective Laser Melting

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 528
Author(s):  
Chunyue Yin ◽  
Zhehao Lu ◽  
Xianshun Wei ◽  
Biao Yan ◽  
Pengfei Yan
Keyword(s):  
Selective Laser Melting ◽  
Bending Strength ◽  
Primary Silicon ◽  
Processing Parameters ◽  
Powder Materials ◽  
Laser Melting ◽  
Maximum Value ◽  
Fine Microstructure ◽  
Average Size ◽  
Al Matrix

The objective of the study is to investigate the corresponding microstructure and mechanical properties, especially bending strength, of the hypereutectic Al-Si alloy processed by selective laser melting (SLM). Almost dense Al-22Si-0.2Fe-0.1Cu-Re alloy is fabricated from a novel type of powder materials with optimized processing parameters. Phase analysis of such Al-22Si-0.2Fe-0.1Cu-Re alloy shows that the solubility of Si in Al matrix increases significantly. The fine microstructure can be observed, divided into three zones: fine zones, coarse zones, and heat-affected zones (HAZs). Fine zones are directly generated from the liquid phase with the characteristic of petaloid structures and bulk Al-Si eutectic. Due to the fine microstructure induced by the rapid cooling rate of SLM, the primary silicon presents a minimum average size of ~0.5 μm in fine zones, significantly smaller than that in the conventional produced hypereutectic samples. Moreover, the maximum value of Vickers hardness reaches ~170 HV0.2, and bending strength increases to 687.70 MPa for the as-built Al-22Si-0.2Fe-0.1Cu-Re alloys parts, which is much higher than that of cast counterparts. The formation mechanism of this fine microstructure and the enhancement reasons of bending strength are also discussed.

Step-by-step generation of aluminum grain structure produced by selective laser melting

2020 ◽  
Author(s):  
E. Dymnich ◽  
V. A. Romanova ◽  
R. R. Balokhonov ◽  
O. Zinovieva
Keyword(s):  
Selective Laser Melting ◽  
Grain Structure ◽  
Laser Melting ◽  
Step Generation

scholarly journals Effect of Process Parameters and High-Temperature Preheating on Residual Stress and Relative Density of Ti6Al4V Processed by Selective Laser Melting

Materials ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 930 ◽  
Author(s):  
Martin Malý ◽  
Christian Höller ◽  
Mateusz Skalon ◽  
Benjamin Meier ◽  
Daniel Koutný ◽  
...  
Keyword(s):  
Residual Stress ◽  
High Temperature ◽  
Residual Stresses ◽  
Relative Density ◽  
Selective Laser Melting ◽  
Process Parameters ◽  
Stress Reduction ◽  
Laser Melting ◽  
Preheating Temperature ◽  
Laser Velocity

The aim of this study is to observe the effect of process parameters on residual stresses and relative density of Ti6Al4V samples produced by Selective Laser Melting. The investigated parameters were hatch laser power, hatch laser velocity, border laser velocity, high-temperature preheating and time delay. Residual stresses were evaluated by the bridge curvature method and relative density by the optical method. The effect of the observed process parameters was estimated by the design of experiment and surface response methods. It was found that for an effective residual stress reduction, the high preheating temperature was the most significant parameter. High preheating temperature also increased the relative density but caused changes in the chemical composition of Ti6Al4V unmelted powder. Chemical analysis proved that after one build job with high preheating temperature, oxygen and hydrogen content exceeded the ASTM B348 limits for Grade 5 titanium.

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