Research

15 pages, 10260 KiB

Open AccessArticle

Rapid Alloy Development of Extremely High-Alloyed Metals Using Powder Blends in Laser Powder Bed Fusion

by Simon Ewald, Fabian Kies, Steffen Hermsen, Maximilian Voshage, Christian Haase and Johannes Henrich Schleifenbaum

Materials 2019, 12(10), 1706; https://doi.org/10.3390/ma12101706 - 26 May 2019

Cited by 52 | Viewed by 5339

Abstract

The design of new alloys by and for metal additive manufacturing (AM) is an emerging field of research. Currently, pre-alloyed powders are used in metal AM, which are expensive and inflexible in terms of varying chemical composition. The present study describes the adaption [...] Read more.

The design of new alloys by and for metal additive manufacturing (AM) is an emerging field of research. Currently, pre-alloyed powders are used in metal AM, which are expensive and inflexible in terms of varying chemical composition. The present study describes the adaption of rapid alloy development in laser powder bed fusion (LPBF) by using elemental powder blends. This enables an agile and resource-efficient approach to designing and screening new alloys through fast generation of alloys with varying chemical compositions. This method was evaluated on the new and chemically complex materials group of multi-principal element alloys (MPEAs), also known as high-entropy alloys (HEAs). MPEAs constitute ideal candidates for the introduced methodology due to the large space for possible alloys. First, process parameters for LPBF with powder blends containing at least five different elemental powders were developed. Secondly, the influence of processing parameters and the resulting energy density input on the homogeneity of the manufactured parts were investigated. Microstructural characterization was carried out by optical microscopy, electron backscatter diffraction (EBSD), and energy-dispersive X-ray spectroscopy (EDS), while mechanical properties were evaluated using tensile testing. Finally, the applicability of powder blends in LPBF was demonstrated through the manufacture of geometrically complex lattice structures with energy absorption functionality. Full article

(This article belongs to the Special Issue Metal Materials and Non-conventional Mechanical Manufacturing Processes)

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12 pages, 5596 KiB

Open AccessArticle

On-Line Monitoring of Blind Fastener Installation Process

by Javier Camacho, Fernando Veiga, Mari Luz Penalva, Alberto Diez-Olivan, Lutz Deitert and Norberto López de Lacalle

Materials 2019, 12(7), 1157; https://doi.org/10.3390/ma12071157 - 10 Apr 2019

Cited by 3 | Viewed by 3169

Abstract

Blind fasteners are of special interest for aircraft construction since they allow working on joints where only one side is accessible, as is the case in many common aerospace box-type structures, such as stabilizers and flaps. This paper aims to deliver an online [...] Read more.

Blind fasteners are of special interest for aircraft construction since they allow working on joints where only one side is accessible, as is the case in many common aerospace box-type structures, such as stabilizers and flaps. This paper aims to deliver an online monitoring method for the detection of incorrect installed blind fasteners. In this type of fastener, the back side of the assembly is not accessible, so monitoring the process installation is suitable as a system to assess the formed head at the back side with no access. The solution proposed consists of an on-line monitoring system that is based on sensor signals acquired during the installation. The signals are conveniently analyzed in order to provide an evaluation outcome on how the fastener was installed. This new method will help production to decrease/eliminate time and cost-intensive inspections and fasteners over installation in structures. The decrease of the number of installed fasteners will also contribute to weight savings and will reduce the use of resources. Full article

(This article belongs to the Special Issue Metal Materials and Non-conventional Mechanical Manufacturing Processes)

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22 pages, 6359 KiB

Open AccessArticle

A Study on the Thermal Effect by Multi Heat Sources and Machining Characteristics of Laser and Induction Assisted Milling

by Jae-Hyeon Ha and Choon-Man Lee

Materials 2019, 12(7), 1032; https://doi.org/10.3390/ma12071032 - 28 Mar 2019

Cited by 17 | Viewed by 3830

Abstract

Thermally assisted machining (TAM) is an effective method for difficult-to-cut materials, and works by locally preheating the workpiece using various heat sources, such as laser, induction, and plasma. Recently, many researchers have studied TAM because of its low manufacturing costs, high productivity, and [...] Read more.

Thermally assisted machining (TAM) is an effective method for difficult-to-cut materials, and works by locally preheating the workpiece using various heat sources, such as laser, induction, and plasma. Recently, many researchers have studied TAM because of its low manufacturing costs, high productivity, and quality of materials. Laser assisted machining (LAM) has been studied by many researchers, but studies on TAM using induction or plasma heat sources, which are much cheaper than lasers, have been carried out by only a few researchers. Lasers have an excellent preheating effect, but are expensive, and the temperature of the heated workpiece drops quickly. Here, multi heat sources were used to solve the shortage in supplied heat source with a single heat source. Induction was applied as an additional heat source. The purpose of this study is to analyze the thermal effect and temperature distribution of single heat source and multi heat sources, and compare the machining characteristics according to heat source types. In order to analyze the preheating effect according to the feed rate of the heat sources, a temperature measurement experiment using thermocouples was carried out, and the efficiency of the thermal effect using multi heat sources was verified. In addition, the effectiveness of the thermal analysis results was verified by comparison with the measured temperature distribution. The machining characteristics of Inconel 718 and Ti-6Al-4V with laser, induction, and laser-induction assisted milling (LIAMill) were analyzed, by cutting force and surface roughness. Full article

(This article belongs to the Special Issue Metal Materials and Non-conventional Mechanical Manufacturing Processes)

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12 pages, 5412 KiB

Open AccessArticle

Current-Induced Ductility Enhancement of a Magnesium Alloy AZ31 in Uniaxial Micro-Tension Below 373 K

by Xinwei Wang, Antonio J. Sánchez Egea, Jie Xu, Xianyu Meng, Zhenlong Wang, Debin Shan, Bin Guo and Jian Cao

Materials 2019, 12(1), 111; https://doi.org/10.3390/ma12010111 - 31 Dec 2018

Cited by 13 | Viewed by 3847

Abstract

The size effects in metal forming have been found to be crucial in micro-scale plastic deformation or micro-forming processes, which lead to attenuation of the material’s formability due to the increasing heterogeneity of the plastic flow. The use of an electric field during [...] Read more.

The size effects in metal forming have been found to be crucial in micro-scale plastic deformation or micro-forming processes, which lead to attenuation of the material’s formability due to the increasing heterogeneity of the plastic flow. The use of an electric field during micro-scale plastic deformation has shown to relieve size effects, enhance the material’s formability, modify the microstructure, etc. Consequently, these electric-assisted (EA) micro-forming processes seem to bring many potential benefits that need to be investigated. Accordingly, here we investigated the influence of an electric field on the size effects to describe the fracture behavior in uniaxial micro-tension tests of an AZ31 alloy with various grain sizes. In order to decouple the thermal-mechanical and microstructure changes, room temperature (RT), oven-heated (OH), air-cooled (AC), and EA uniaxial micro-tension tests were conducted. The size effects contribution on the fracture stress and strain showed a similar trend in all the testing configurations. However, the smallest fracture stresses and the largest fracture strains were denoted in the EA configuration. EBSD examination shows that current-induced dynamic recrystallization (DRX) and texture evolution could be negligible under the studied conditions. The kernel average misorientation (KAM) maps give the larger plastic deformation in the EA specimens due to the reduction of plastic micro-heterogeneity. Finally, the fracture morphology indicates that the current-induced ductility enhancement may be attributed to the arrest of micro-crack propagation and the inhibition of void initiation, growth, and coalescence caused by lattice melting and expansion. Full article

(This article belongs to the Special Issue Metal Materials and Non-conventional Mechanical Manufacturing Processes)

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15 pages, 3101 KiB

Open AccessArticle

Comparative Analysis of Mechanical Properties and Metal-Ceramic Bond Strength of Co-Cr Dental Alloy Fabricated by Different Manufacturing Processes

by Xingting Han, Tomofumi Sawada, Christine Schille, Ernst Schweizer, Lutz Scheideler, Jürgen Geis-Gerstorfer, Frank Rupp and Sebastian Spintzyk

Materials 2018, 11(10), 1801; https://doi.org/10.3390/ma11101801 - 22 Sep 2018

Cited by 67 | Viewed by 7782

Abstract

Cobalt-chromium (Co-Cr) alloy is a widely used base material for dental fixed prostheses. These restorations can be produced through casting technique, subtractive or additive manufacturing technologies. However, limited information is available regarding the influence of manufacturing techniques on the properties of Co-Cr alloy [...] Read more.

Cobalt-chromium (Co-Cr) alloy is a widely used base material for dental fixed prostheses. These restorations can be produced through casting technique, subtractive or additive manufacturing technologies. However, limited information is available regarding the influence of manufacturing techniques on the properties of Co-Cr alloy since most studies used different chemical compositions of Co-Cr alloy for different manufacturing methods. This study compares the mechanical properties, metal-ceramic bond strength, and microstructures of specimens produced by casting, milling, and selective laser melting (SLM) from one single Co-Cr alloy composition. The mechanical properties of the alloy were investigated by tensile and Vickers hardness tests, and metal-ceramic bond strength was determined by three-point bending. Scanning electron microscopy (SEM) with backscattered electron (BSE) images and optical microphotographs were used to analyze the surface microstructures. Compared with the casting and milling techniques, SLM Co-Cr alloy specimens indicated enhanced mechanical properties and comparable metal-ceramic bond strength. Besides, the microstructures of the SLM specimens showed finer grains with more second phase particles than the casting and milling specimens. The results of our study indicate that SLM might be superior to traditional techniques for the manufacturing of fixed dental restorations. Full article

(This article belongs to the Special Issue Metal Materials and Non-conventional Mechanical Manufacturing Processes)

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14 pages, 8666 KiB

Open AccessArticle

An Innovative Method for Forming Balls by Cross Rolling

by Zbigniew Pater, Janusz Tomczak and Tomasz Bulzak

Materials 2018, 11(10), 1793; https://doi.org/10.3390/ma11101793 - 21 Sep 2018

Cited by 6 | Viewed by 3178

Abstract

The paper describes an innovative cross rolling method that enables the production of six balls at the same time, each ball with a diameter of 100 mm. The principle of the proposed rolling technique is discussed and the tools used in this forming [...] Read more.

The paper describes an innovative cross rolling method that enables the production of six balls at the same time, each ball with a diameter of 100 mm. The principle of the proposed rolling technique is discussed and the tools used in this forming process are described. Two variations of the proposed method for producing balls were investigated, one performed with the use of flat tools and the other with the use of two rolls. Results of the numerical modelling are discussed. They clearly demonstrate that the proposed method can be used to produce balls with large diameters. Rolling experiments were performed under laboratory conditions to produce 40 mm diameter balls, i.e., in the 1:2.5 scale. The experimental findings show a good qualitative agreement with the numerical results. Full article

(This article belongs to the Special Issue Metal Materials and Non-conventional Mechanical Manufacturing Processes)

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17 pages, 14908 KiB

Open AccessArticle

Effect of Die Geometry on the Formability of 5052 Aluminum Alloy in Electromagnetic Impaction Deformation

by Fei Feng, Jianjun Li, Rongchuang Chen, Peng Yuan, Hongliang Su, Qixian Zhang, Pan Huang and Zhizhen Zheng

Materials 2018, 11(8), 1379; https://doi.org/10.3390/ma11081379 - 08 Aug 2018

Cited by 14 | Viewed by 3224

Abstract

The formability of aluminum alloy sheet in electromagnetic impaction deformation has attracted the attention of numerous researchers for the past decades. However, the influences of die geometry and high-speed impaction electromagnetic deformation on formability have not been well established, thereby resulting in the [...] Read more.

The formability of aluminum alloy sheet in electromagnetic impaction deformation has attracted the attention of numerous researchers for the past decades. However, the influences of die geometry and high-speed impaction electromagnetic deformation on formability have not been well established, thereby resulting in the formability of the sheet not being developed fully. In this study, the influence of die geometry on the formability of 5052 aluminum alloy in electromagnetic deformation was investigated by comparing the formability of 5052 aluminum alloys formed using a hemispherical die and a cylindrical die. The intriguing finding is that the formability of the 5052 aluminum alloy formed using a cylindrical die is considerably higher than that formed using a hemispherical die. Therefore, die geometry significantly influences the formability of 5052 aluminum alloy. The influence of die geometry on the formability of 5052 aluminum alloy in high-speed impaction electromagnetic deformation was explained in terms of strain rate, pressure stress, and stress state. This investigation enhances insight into the interaction between sheets and dies, and provides a reference for the studying influence of dies on the forming limit of sheets in high-speed impaction deformation. Full article

(This article belongs to the Special Issue Metal Materials and Non-conventional Mechanical Manufacturing Processes)

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19 pages, 26523 KiB

Open AccessArticle

Numerical Simulation and Experimental Validation of Sheet Laser Forming Processes Using General Scanning Paths

by Álvaro Navarrete, Felipe Cook, Diego Celentano, Marcela Cruchaga and Claudio García-Herrera

Materials 2018, 11(7), 1262; https://doi.org/10.3390/ma11071262 - 23 Jul 2018

Cited by 6 | Viewed by 3476

Abstract

This work presents numerical simulations and an experimental validation of sheet laser forming processes using general scanning paths with different laser beam operating parameters (i.e., power, diameter, and scanning speed) in two specific graphite coated stainless steel blanks (i.e., with thicknesses of 0.3 [...] Read more.

This work presents numerical simulations and an experimental validation of sheet laser forming processes using general scanning paths with different laser beam operating parameters (i.e., power, diameter, and scanning speed) in two specific graphite coated stainless steel blanks (i.e., with thicknesses of 0.3 mm and 0.6 mm for the AISI 302 and 304 alloys, respectively). To this end, three specific laser forming tests involving single S-shaped, multiple circular, and single piecewise linear scanning paths are carried out. On the other hand, the numerical simulation of these tests is performed via a coupled thermomechanical finite element formulation, accounting for large viscoplastic strains, temperature-dependent material properties, and convection-radiation phenomena. The final bending angles provided by this model are found to be in good agreement with the experimental measurements for all of the cases studied. Therefore, this modeling framework can be established as a reliable approach to predict the material thermomechanical response during sheet laser forming using general scanning paths. Full article

(This article belongs to the Special Issue Metal Materials and Non-conventional Mechanical Manufacturing Processes)

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