Forming feasibility and interface microstructure of Al/Cu bimetallic structure fabricated by laser powder bed fusion

Purpose The purpose of this paper is to analyze and investigate heat accumulation caused by temperature changes and interface microstructure effected by element diffusion. Design/methodology/approach Al/Cu bimetallic structure is initially manufactured through laser powder bed fusion process. To minimize trial and error, finite element modeling is adopted to simulate temperature changes on the Al-based and Cu-based substrate. Findings The results show that forming pure copper on Al-based substrate can guarantee heat accumulation, providing enough energy for subsequent building. The instantaneous laser energy promotes increase of diffusion activation energy, resulting in the formation of transition zone derived from interdiffusion between Al and Cu atoms. The interface with a thickness of about 22 µm dominated by Kirkendall effect moves towards Al-rich side. The interface microstructure is mainly composed of a-Al, a-Cu and CuAl2 phase. Originality/value The bonding mechanism of Al/Cu interface is atom diffusion-induced chemical reaction. The theoretical basis provides guidance for structural design and production application.

Download Full-text

Influence of Laser Energy Input and Shielding Gas Flow on Evaporation Fume during Laser Powder Bed Fusion of Zn Metal

Materials ◽

10.3390/ma14102677 ◽

2021 ◽

Vol 14 (10) ◽

pp. 2677

Author(s):

Yu Qin ◽

Jinge Liu ◽

Yanzhe Chen ◽

Peng Wen ◽

Yufeng Zheng ◽

...

Keyword(s):

Energy Input ◽

Gas Flow ◽

Evaporation Rate ◽

Laser Energy ◽

Circulation System ◽

Powder Bed Fusion ◽

Shielding Gas ◽

Laser Powder Bed Fusion ◽

Conservation Of Energy ◽

Powder Bed

Laser powder bed fusion (LPBF) of Zn-based metals exhibits prominent advantages to produce customized biodegradable implants. However, massive evaporation occurs during laser melting of Zn so that it becomes a critical issue to modulate laser energy input and gas shielding conditions to eliminate the negative effect of evaporation fume during the LPBF process. In this research, two numerical models were established to simulate the interaction between the scanning laser and Zn metal as well as the interaction between the shielding gas flow and the evaporation fume, respectively. The first model predicted the evaporation rate under different laser energy input by taking the effect of evaporation on the conservation of energy, momentum, and mass into consideration. With the evaporation rate as the input, the second model predicted the elimination effect of evaporation fume under different conditions of shielding gas flow by taking the effect of the gas circulation system including geometrical design and flow rate. In the case involving an adequate laser energy input and an optimized shielding gas flow, the evaporation fume was efficiently removed from the processing chamber during the LPBF process. Furthermore, the influence of evaporation on surface quality densification was discussed by comparing LPBF of pure Zn and a Titanium alloy. The established numerical analysis not only helps to find the adequate laser energy input and the optimized shielding gas flow for the LPBF of Zn based metal, but is also beneficial to understand the influence of evaporation on the LPBF process.

Download Full-text

High-precision laser powder bed fusion processing of pure copper

Additive Manufacturing ◽

10.1016/j.addma.2021.102417 ◽

2021 ◽

pp. 102417

Author(s):

Shuo Qu ◽

Junhao Ding ◽

Jin Fu ◽

Mingwang Fu ◽

Baicheng Zhang ◽

...

Keyword(s):

High Precision ◽

Pure Copper ◽

Powder Bed Fusion ◽

Laser Powder Bed Fusion ◽

Powder Bed

Download Full-text

A printability assessment framework for fabricating low variability nickel-niobium parts using laser powder bed fusion additive manufacturing

Rapid Prototyping Journal ◽

10.1108/rpj-01-2021-0024 ◽

2021 ◽

Vol ahead-of-print (ahead-of-print) ◽

Author(s):

Bing Zhang ◽

Raiyan Seede ◽

Austin Whitt ◽

David Shoukr ◽

Xueqin Huang ◽

...

Keyword(s):

Mechanical Properties ◽

Additive Manufacturing ◽

Uncertainty Quantification ◽

Process Optimization ◽

Powder Bed Fusion ◽

Assessment Framework ◽

Laser Powder Bed Fusion ◽

Content Type ◽

Powder Bed ◽

Analytical Thermal Model

Purpose There is recent emphasis on designing new materials and alloys specifically for metal additive manufacturing (AM) processes, in contrast to AM of existing alloys that were developed for other traditional manufacturing methods involving considerably different physics. Process optimization to determine processing recipes for newly developed materials is expensive and time-consuming. The purpose of the current work is to use a systematic printability assessment framework developed by the co-authors to determine windows of processing parameters to print defect-free parts from a binary nickel-niobium alloy (NiNb5) using laser powder bed fusion (LPBF) metal AM. Design/methodology/approach The printability assessment framework integrates analytical thermal modeling, uncertainty quantification and experimental characterization to determine processing windows for NiNb5 in an accelerated fashion. Test coupons and mechanical test samples were fabricated on a ProX 200 commercial LPBF system. A series of density, microstructure and mechanical property characterization was conducted to validate the proposed framework. Findings Near fully-dense parts with more than 99% density were successfully printed using the proposed framework. Furthermore, the mechanical properties of as-printed parts showed low variability, good tensile strength of up to 662 MPa and tensile ductility 51% higher than what has been reported in the literature. Originality/value Although many literature studies investigate process optimization for metal AM, there is a lack of a systematic printability assessment framework to determine manufacturing process parameters for newly designed AM materials in an accelerated fashion. Moreover, the majority of existing process optimization approaches involve either time- and cost-intensive experimental campaigns or require the use of proprietary computational materials codes. Through the use of a readily accessible analytical thermal model coupled with statistical calibration and uncertainty quantification techniques, the proposed framework achieves both efficiency and accessibility to the user. Furthermore, this study demonstrates that following this framework results in printed parts with low degrees of variability in their mechanical properties.

Download Full-text

On the manufacturability of Inconel 718 thin-walled honeycomb structures by laser powder bed fusion

Rapid Prototyping Journal ◽

10.1108/rpj-04-2021-0098 ◽

2021 ◽

Vol ahead-of-print (ahead-of-print) ◽

Author(s):

José M. Zea Pérez ◽

Jorge Corona-Castuera ◽

Carlos Poblano-Salas ◽

John Henao ◽

Arturo Hernández Hernández

Keyword(s):

Mechanical Properties ◽

Inconel 718 ◽

Dimensional Accuracy ◽

Honeycomb Lattice ◽

Lattice Structures ◽

Powder Bed Fusion ◽

Laser Powder Bed Fusion ◽

Content Type ◽

Powder Bed ◽

Thin Walled

Purpose The purpose of this paper is to study the effects of printing strategies and processing parameters on wall thickness, microhardness and compression strength of Inconel 718 superalloy thin-walled honeycomb lattice structures manufactured by laser powder bed fusion (L-PBF). Design/methodology/approach Two printing contour strategies were applied for producing thin-walled honeycomb lattice structures in which the laser power, contour path, scanning speed and beam offset were systematically modified. The specimens were analyzed by optical microscopy for dimensional accuracy. Vickers hardness and quasi-static uniaxial compression tests were performed on the specimens with the least difference between the design wall thickness and the as built one to evaluate their mechanical properties and compare them with the counterparts obtained by using standard print strategies. Findings The contour printing strategies and process parameters have a significant influence on reducing the fabrication time of thin-walled honeycomb lattice structures (up to 50%) and can lead to improve the manufacturability and dimensional accuracy. Also, an increase in the young modulus up to 0.8 times and improvement in the energy absorption up to 48% with respect to those produced by following a standard strategy was observed. Originality/value This study showed that printing contour strategies can be used for faster fabrication of thin-walled lattice honeycomb structures with similar mechanical properties than those obtained by using a default printing strategy.

Download Full-text

Camera signal dependencies within coaxial melt pool monitoring in laser powder bed fusion

Rapid Prototyping Journal ◽

10.1108/rpj-01-2019-0022 ◽

2020 ◽

Vol 26 (1) ◽

pp. 100-106 ◽

Cited By ~ 1

Author(s):

Tobias Kolb ◽

Reza Elahi ◽

Jan Seeger ◽

Mathews Soris ◽

Christian Scheitler ◽

...

Keyword(s):

Surface Roughness ◽

Layer Thickness ◽

Powder Layer ◽

Powder Bed Fusion ◽

Laser Powder Bed Fusion ◽

Content Type ◽

Powder Bed ◽

Sensory Signals ◽

Melt Pool ◽

Research Activities

Purpose The purpose of this paper is to analyse the signal dependency of the camera-based coaxial monitoring system QMMeltpool 3D (Concept Laser GmbH, Lichtenfels, Germany) for laser powder bed fusion (LPBF) under the variation of process parameters, position, direction and layer thickness to determine the capability of the system. Because such and similar monitoring systems are designed and presented for quality assurance in series production, it is important to present the dominant signal influences and limitations. Design/methodology/approach Hardware of the commercially available coaxial monitoring QMMeltpool 3D is used to investigate the thermal emission of the interaction zone during LPBF. The raw images of the camera are analysed by means of image processing to bypass the software of QMMeltpool 3D and to gain a high level of signal understanding. Laser power, scan speed, laser spot diameter and powder layer thickness were varied for single-melt tracks to determine the influence of a parameter variation on the measured sensory signals. The effects of the scan direction and position were also analysed in detail. The influence of surface roughness on the detected sensory signals was simulated by a machined substrate plate. Findings Parameter variations are confirmed to be detectable. Because of strong directional and positional dependencies of the melt-pool monitoring signal a calibration algorithm is necessary. A decreasing signal is detected for increasing layer thickness. Surface roughness is identified as a dominating factor with major influence on the melt-pool monitoring signal exceeding other process flaws. Research limitations/implications This work was performed with the hardware of a commercially available QMMeltpool 3D system of an LPBF machine M2 of the company Concept Laser GmbH. The results are relevant for all melt-pool monitoring research activities connected to LPBF, as well as for end users and serial production. Originality/value Surface roughness has not yet been revealed as being one of the most important origins for signal deviations in coaxial melt-pool monitoring. To the best of the authors’ knowledge, the direct comparison of influences because of parameters and environment has not been published to this extent. The detection, evaluation and remelting of surface roughness constitute a plausible workflow for closed-loop control in LPBF.

Download Full-text

Realistic design of laser powder bed fusion channels

Rapid Prototyping Journal ◽

10.1108/rpj-01-2020-0010 ◽

2020 ◽

Vol 26 (10) ◽

pp. 1827-1836

Author(s):

Christopher Gottlieb Klingaa ◽

Sankhya Mohanty ◽

Jesper Henri Hattel

Keyword(s):

Surface Roughness ◽

Prediction Models ◽

Powder Bed Fusion ◽

Laser Powder Bed Fusion ◽

Channel Design ◽

Conformal Cooling ◽

Content Type ◽

Powder Bed ◽

Cooling Channels ◽

Conformal Cooling Channels

Purpose Conformal cooling channels in additively manufactured molds are superior over conventional channels in terms of cooling control, part warpage and lead time. The heat transfer ability of cooling channels is determined by their geometry and surface roughness. Laser powder bed fusion manufactured channels have an inherent process-induced dross formation that may significantly alter the actual shape of nominal channels. Therefore, it is crucial to be able to predict the expected surface roughness and changes in the geometry of metal additively manufactured conformal cooling channels. The purpose of this paper is to present a new methodology for predicting the realistic design of laser powder bed fusion channels. Design/methodology/approach This study proposes a methodology for making nominal channel design more realistic by the implementation of roughness prediction models. The models are used for altering the nominal shape of a channel to its predicted shape by point cloud analysis and manipulation. Findings A straight channel is investigated as a simple case study and validated against X-ray computed tomography measurements. The modified channel geometry is reconstructed and meshed, resulting in a predicted, more realistic version of the nominal geometry. The methodology is successfully tested on a torus shape and a simple conformal cooling channel design. Finally, the methodology is validated through a cooling test experiment and comparison with simulations. Practical implications Accurate prediction of channel surface roughness and geometry would lead toward more accurate modeling of cooling performance. Originality/value A robust start to finish method for realistic geometrical prediction of metal additive manufacturing cooling channels has yet to be proposed. The current study seeks to fill the gap.

Download Full-text

Laser powder bed fusion additive manufacturing of copper wicking structures: fabrication and capillary characterization

Rapid Prototyping Journal ◽

10.1108/rpj-01-2021-0016 ◽

2021 ◽

Vol ahead-of-print (ahead-of-print) ◽

Author(s):

Adnen Mezghani ◽

Abdalla R. Nassar ◽

Corey J. Dickman ◽

Eduardo Valdes ◽

Raul Alvarado

Keyword(s):

Additive Manufacturing ◽

Design Methodology ◽

Heat Pipes ◽

Powder Bed Fusion ◽

Laser Powder Bed Fusion ◽

Content Type ◽

Powder Bed ◽

Published Report ◽

Secondary Manufacturing ◽

Design Freedom

Purpose An integral component in heat pipes (HPs) and vapor chambers (VCs) is a porous wicking structure. Traditional methods for manufacturing wicking structures within HPs and VCs involve secondary manufacturing processes and are generally limited to simple geometries. This work aims to leverage the unprecedented level of design freedom of laser powder bed fusion (LPBF) additive manufacturing (AM) to produce integrated wicking structures for HPs and VCs. Design/methodology/approach Copper wicking structures are fabricated through LPBF via partial sintering and via the formation of square, hexagonal and rectangular arrangements of micro-pins and micro-grooves, produced in multiple build directions. Wicks are characterized by conducting capillary performance analysis through the measurement of porosity, permeability and capillary rate-of-rise. Findings Copper wicking structures were successfully fabricated with capillary performance, K/reff, ranging from 0.186–1.74 µm. The rectangular-arrangement micro-pin wick presented the highest performance. Originality/value This work represents the first published report on LPBF AM of copper wicking structures for HPs/VCs applications and represents foundational knowledge for fabricating complete assemblies of copper VCs and HPs through LPBF AM.

Download Full-text

Electrical resistivity of pure copper processed by medium-powered laser powder bed fusion additive manufacturing for use in electromagnetic applications

Additive Manufacturing ◽

10.1016/j.addma.2019.100831 ◽

2019 ◽

Vol 29 ◽

pp. 100831 ◽

Cited By ~ 9

Author(s):

Cassidy Silbernagel ◽

Leonidas Gargalis ◽

Ian Ashcroft ◽

Richard Hague ◽

Michael Galea ◽

...

Keyword(s):

Electrical Resistivity ◽

Additive Manufacturing ◽

Pure Copper ◽

Powder Bed Fusion ◽

Laser Powder Bed Fusion ◽

Powder Bed

Download Full-text

Effect of Laser Energy Density on the Microstructure andTexture Evolution of Hastelloy-X Alloy Fabricated by Laser Powder Bed Fusion

Materials ◽

10.3390/ma14154305 ◽

2021 ◽

Vol 14 (15) ◽

pp. 4305

Author(s):

Shuzhe Zhang ◽

Yunpei Lei ◽

Zhen Chen ◽

Pei Wei ◽

Wenjie Liu ◽

...

Keyword(s):

Grain Size ◽

Energy Density ◽

Electron Backscatter Diffraction ◽

Laser Energy ◽

Primary Dendrite ◽

Powder Bed Fusion ◽

Laser Powder Bed Fusion ◽

Hastelloy X ◽

Powder Bed ◽

Average Grain Size

It is of great importance to study the microstructure and textural evolution of laser powder bed fusion (LPBF) formed Hastelloy-X alloys, in order to establish a close relationship between the process, microstructure, and properties through the regulation of the Hastelloy-X formation process parameters. In this paper, components of a Hastelloy-X alloy were formed with different laser energy densities (also known as the volume energy density VED). The densification mechanism of Hastelloy-X was studied, and the causes of defects, such as pores and cracks, were analyzed. The influence of different energy densities on grain size, texture, and orientation was investigated using an electron backscatter diffraction technique. The results show that the average grain size, primary dendrite arm spacing, and number of low angle grain boundaries increased with the increase of energy density. At the same time, the VED can strengthen the texture. The textural intensity increases with the increase of energy density. The best mechanical properties were obtained at the VED of 96 J·mm−3.

Download Full-text