scholarly journals Selective Laser Melting of Aluminum and Its Alloys

Materials ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 4564 ◽  
Author(s):  
Zhi Wang ◽  
Raghunandan Ummethala ◽  
Neera Singh ◽  
Shengyang Tang ◽  
Challapalli Suryanarayana ◽  
...  
Keyword(s):  
Selective Laser Melting ◽  
Processing Parameters ◽  
Fatigue Properties ◽  
Internal Stresses ◽  
Surface Oxide Layer ◽  
Alloy Development ◽  
Laser Melting ◽  
Powder Bed ◽  
Microstructure Evaluation ◽  
Melt Cooling

The laser-based powder bed fusion (LBPF) process or commonly known as selective laser melting (SLM) has made significant progress since its inception. Initially, conventional materials like 316L, Ti6Al4V, and IN-718 were fabricated using the SLM process. However, it was inevitable to explore the possible fabrication of the second most popular structural material after Fe-based alloys/steel, the Al-based alloys by SLM. Al-based alloys exhibit some inherent difficulties due to the following factors: the presence of surface oxide layer, solidification cracking during melt cooling, high reflectivity from the surface, high thermal conductivity of the metal, poor flowability of the powder, low melting temperature, etc. Researchers have overcome these difficulties to successfully fabricate the different Al-based alloys by SLM. However, there exists no review dealing with the fabrication of different Al-based alloys by SLM, their fabrication issues, microstructure, and their correlation with properties in detail. Hence, the present review attempts to introduce the SLM process followed by a detailed discussion about the processing parameters that form the core of the alloy development process. This is followed by the current research status on the processing of Al-based alloys and microstructure evaluation (including defects, internal stresses, etc.), which are dealt with on the basis of individual Al-based series. The mechanical properties of these alloys are discussed in detail followed by the other important properties like tribological properties, fatigue properties, etc. Lastly, an outlook is given at the end of this review.

scholarly journals High and low-cycle-fatigue properties of 17–4 PH manufactured via selective laser melting in as-built, machined and hipped conditions

2021 ◽  
Author(s):  
Franco Concli ◽  
Lorenzo Fraccaroli ◽  
Filippo Nalli ◽  
Luca Cortese
Keyword(s):  
Selective Laser Melting ◽  
High Cycle Fatigue ◽  
Low Cycle Fatigue ◽  
The Other ◽  
Fatigue Properties ◽  
Surface Finishing ◽  
Powder Bed Fusion ◽  
Cycle Fatigue ◽  
Laser Melting ◽  
Powder Bed

AbstractIn the last years, additive manufacturing (AM) has turned into an emerging technology and an increasing number of classes of material powders are now available for this manufacturing process. For large-scale adoption, an accurate knowledge of the mechanical behaviour of the resulting materials is fundamental, also considering that reliable data are often lacking and dedicated standards are still missing for these AM alloys. In this regard, the aim of the present work is to characterize both the high-cycle-fatigue (HFC) and the low-cycle-fatigue (LCF) behaviour of AM 17–4 PH stainless steel (SS). To better understand the performance of the selected alloy, four series of cylindrical samples were manufactured. Three series were produced via selective laser melting (SLM), better known as laser-based powder bed fusion of metals technology using an EOS M280 machine. The first series was tested in the as-built condition, the second was machined before testing to obtain a better surface finishing, while the third series was post-processed via hot isostatic pressing (HIP). Finally, a fourth series of samples was produced from the wrought 17–4 PH material counterpart, for comparison. The understanding and assessment of the influence of surface finishing on the fatigue behaviour of AM materials are fundamental, considering that in most applications the AM parts may present reticular or lattice structures, internal cavities or complex geometries, which must be set into operation in the as-built conditions, since a surface finishing postprocess is not convenient or not feasible at all. On the other side, a HIP process is often suggested to reduce the internal porosities and, therefore, to improve the resulting mechanical properties. The high-cycle-fatigue limits were obtained with a short staircase approach according to the Dixon statistical method. The maximum number of cycles (run-out) was set equal to 50,00,000. The part of the Wöhler diagram relative to finite life was also characterized by means of additional tests at higher stress levels. On the other side, the low-cycle tests allowed to tune the Ramberg–Osgood cyclic curves and the Basquin–Coffin–Manson LCF curves. The results obtained for the four different series of specimens permitted to quantify the reduction of the mechanical performance due to the actual limits of the laser-based powder bed fusion technology (surface quality, internal porosity, different solidification) with respect to traditional manufacturing and could be used to improve design safety and reliability, granting structural integrity of actual applications under elastic and elasto-plastic fatigue loads.

scholarly journals A novel physics-based and data-supported microstructure model for part-scale simulation of laser powder bed fusion of Ti-6Al-4V

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Jonas Nitzler ◽  
Christoph Meier ◽  
Kei W. Müller ◽  
Wolfgang A. Wall ◽  
N. E. Hodge
Keyword(s):  
Selective Laser Melting ◽  
Microstructure Evolution ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Laser Melting ◽  
Cooling Rates ◽  
Powder Bed ◽  
Proposed Model ◽  
Microstructure Model ◽  
Transformation Diagrams

AbstractThe elasto-plastic material behavior, material strength and failure modes of metals fabricated by additive manufacturing technologies are significantly determined by the underlying process-specific microstructure evolution. In this work a novel physics-based and data-supported phenomenological microstructure model for Ti-6Al-4V is proposed that is suitable for the part-scale simulation of laser powder bed fusion processes. The model predicts spatially homogenized phase fractions of the most relevant microstructural species, namely the stable $$\beta $$ β -phase, the stable $$\alpha _{\text {s}}$$ α s -phase as well as the metastable Martensite $$\alpha _{\text {m}}$$ α m -phase, in a physically consistent manner. In particular, the modeled microstructure evolution, in form of diffusion-based and non-diffusional transformations, is a pure consequence of energy and mobility competitions among the different species, without the need for heuristic transformation criteria as often applied in existing models. The mathematically consistent formulation of the evolution equations in rate form renders the model suitable for the practically relevant scenario of temperature- or time-dependent diffusion coefficients, arbitrary temperature profiles, and multiple coexisting phases. Due to its physically motivated foundation, the proposed model requires only a minimal number of free parameters, which are determined in an inverse identification process considering a broad experimental data basis in form of time-temperature transformation diagrams. Subsequently, the predictive ability of the model is demonstrated by means of continuous cooling transformation diagrams, showing that experimentally observed characteristics such as critical cooling rates emerge naturally from the proposed microstructure model, instead of being enforced as heuristic transformation criteria. Eventually, the proposed model is exploited to predict the microstructure evolution for a realistic selective laser melting application scenario and for the cooling/quenching process of a Ti-6Al-4V cube of practically relevant size. Numerical results confirm experimental observations that Martensite is the dominating microstructure species in regimes of high cooling rates, e.g., due to highly localized heat sources or in near-surface domains, while a proper manipulation of the temperature field, e.g., by preheating the base-plate in selective laser melting, can suppress the formation of this metastable phase.

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.

Additive Manufacturing of Glass

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Junjie Luo ◽  
Heng Pan ◽  
Edward C. Kinzel
Keyword(s):  
Additive Manufacturing ◽  
Glass Powder ◽  
Processing Parameters ◽  
Gradient Index ◽  
Continuous Line ◽  
Single Track ◽  
Laser Melting ◽  
Powder Bed ◽  
Transparent Parts ◽  
Insight Into

Selective laser melting (SLM) is a technique for the additive manufacturing (AM) of metals, plastics, and even ceramics. This paper explores using SLM for depositing glass structures. A CO2 laser is used to locally melt portions of a powder bed to study the effects of process parameters on stationary particle formation as well as continuous line quality. Numerical modeling is also applied to gain insight into the physical process. The experimental and numerical results indicate that the absorptivity of the glass powder is nearly constant with respect to the processing parameters. These results are used to deposit layered single-track wide walls to demonstrate the potential of using the SLM process for building transparent parts. Finally, the powder bed process is compared to a wire-fed approach. AM of glass is relevant for gradient index optics, systems with embedded optics, and the formation of hermetic seals.

A SIMULATION STUDY ON THE EFFECT OF PARTICLE SIZE DISTRIBUTION ON THE PRINTED GEOMETRY IN SELECTIVE LASER MELTING

2021 ◽  
pp. 1-14
Author(s):  
Vaishak Ramesh Sagar ◽  
Samuel Lorin ◽  
Johan Göhl ◽  
Johannes Quist ◽  
Christoffer Cromvik ◽  
...  
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Layer Thickness ◽  
Selective Laser Melting ◽  
Laser Melting ◽  
Powder Bed ◽  
Mean Particle Size ◽  
Final Layer ◽  
Effect Of Particle Size

Abstract Selective laser melting (SLM) process is a powder bed fusion additive manufacturing process that finds applications in aerospace and medical industries for its ability to produce complex geometry parts. As the raw material used is in powder form, particle size distribution (PSD) is a significant characteristic that influences the build quality in turn affecting the functionality and aesthetics aspects of the product. This paper investigates the effect of PSD on the printed geometry for 316L stainless steel powder, where three coupled in-house simulation tools based on Discrete Element Method (DEM), Computational Fluid Dynamics (CFD), and Structural Mechanics are employed. DEM is used for simulating the powder bed distribution based on the different powder PSD. The CFD is used as a virtual testbed to determine thermal parameters such as heat capacity and thermal conductivity of the powder bed viewed as a continuum. The values found as a stochastic function of the powder distribution is used to analyse the effect on the melted zone and deformation using Structural Mechanics. Results showed that mean particle size and PSD had a significant effect on the packing density, melt pool layer thickness, and the final layer thickness after deformation. Specifically, a narrow particle size distribution with smaller mean particle size and standard deviation produced solidified final layer thickness closest to nominal layer thickness. The proposed simulation approach and the results will catalyze in development of geometry assurance strategies to minimize the effect of particle size distribution on the geometric quality of the printed part.

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