The effect of different build orientations on the consolidation, tensile and fracture toughness properties of direct metal laser sintering Ti-6Al-4V

2018 ◽  
Vol 24 (2) ◽  
pp. 276-284 ◽  
Author(s):  
Hamza Hassn Alsalla ◽  
Christopher Smith ◽  
Liang Hao
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Laser Sintering ◽  
Full Density ◽  
Full Detail ◽  
Original Research ◽  
Metal Powders ◽  
Direct Metal Laser Sintering ◽  
Cast Material ◽  
Content Type

Purpose The purpose of this paper is to study new process parameters which were selected to achieve the full density of Ti-6Al-4V samples in different building orientations and investigate fracture toughness property and its relation to the microstructure, an area which has not previously been reported in full detail and which may offer information to a designer. Direct metal laser sintering (DMLS) is an additive manufacturing technique that directly manufactures three-dimensional parts, layer-by-layer, to scan and melt metal powders for aerospace applications. Design/methodology/approach Hardness and tensile tests were carried out to evaluate the effect of consolidation on the mechanical performance of specimens made at three different building directions. Optical and electron microscopy were used to characterise the microstructure of the DMLS specimens and their effects on the fractures and mechanical properties. Findings It was found that the built samples have an excellent density at 4.5 g/cm, and the sample surfaces parallel to the building direction are rougher than the perpendicular surfaces. The fracture toughness result was higher than that of the cast material for the same alloy and higher than the Ti-6Al-4V parts fabricated by electron beam melting. This results in the superior mechanical properties of DMLS, while slightly lower in the zy direction owing to cracks, porosity and surface finish. Research limitations/implications The tensile strength was found to be higher than the wrought material, and the samples exhibited brittle fractures owing to the martensitic phase, which is caused by a high temperature gradient, and the mechanical properties change with the change in the microstructures at different building directions. Originality/value This paper contains original research.

Microstructural and fractographic characterization of B4C-Al cermets tested under dynamic and static loading

1989 ◽  
Vol 47 ◽  
pp. 562-563
Author(s):  
Gyeung Ho Kim ◽  
Mehmet Sarikaya ◽  
D. L. Milius ◽  
I. A. Aksay
Keyword(s):  
Thin Film ◽  
Mechanical Properties ◽  
Fracture Toughness ◽  
Static Loading ◽  
Carbon Deposition ◽  
Full Density ◽  
Unique Combination ◽  
Strong Component ◽  
Reaction Products

Cermets are designed to optimize the mechanical properties of ceramics (hard and strong component) and metals (ductile and tough component) into one system. However, the processing of such systems is a problem in obtaining fully dense composite without deleterious reaction products. In the lightweight (2.65 g/cc) B4C-Al cermet, many of the processing problems have been circumvented. It is now possible to process fully dense B4C-Al cermet with tailored microstructures and achieve unique combination of mechanical properties (fracture strength of over 600 MPa and fracture toughness of 12 MPa-m1/2). In this paper, microstructure and fractography of B4C-Al cermets, tested under dynamic and static loading conditions, are described.The cermet is prepared by infiltration of Al at 1150°C into partially sintered B4C compact under vacuum to full density. Fracture surface replicas were prepared by using cellulose acetate and thin-film carbon deposition. Samples were observed with a Philips 3000 at 100 kV.

scholarly journals Mechanical properties comparison of Ti6Al4V produced by different technologies under static load conditions

2019 ◽  
Vol 290 ◽  
pp. 08010
Author(s):  
Karolina Karolewska ◽  
Bogdan Ligaj
Keyword(s):  
Mechanical Properties ◽  
Additive Manufacturing ◽  
Selective Laser Sintering ◽  
Laser Sintering ◽  
Ti6al4v Alloy ◽  
Direct Metal Laser Sintering ◽  
Static Tests ◽  
Rolling Method ◽  
Manufacturing Techniques ◽  
Materials Used

The most commonly used technology among the additive manufacturing is Direct Metal Laser Sintering (DMLS). This process is based on selective laser sintering (SLS). The method gained its popularity due to the possibility of producing metal parts of any geometry, which would be difficult or impossible to obtain by the use of conventional manufacturing techniques. Materials used in the elements manufacturing process are: titanium alloys (e.g. Ti6Al4V), aluminium alloy AlSi10Mg, etc. Elements printed from Ti6Al4V titanium alloy find their application in many industries. Details produced by additive technology are often used in medicine as skeletal, and dental implants. Another example of the DMLS elements use is the aerospace industry. In this area, the additive manufacturing technology produces, i.a. parts of turbines. In addition to the aerospace and medical industries, DMLS technology is also used in motorsport for exhaust pipes or the gearbox parts. The research objects are samples for static tests. These samples were made of Ti6Al4V alloy by the DMLS method and the rolling method from a drawn rod. The aim of the paper is the mechanical properties comparative analysis of the Ti6Al4V alloy produced by the DMLS method under static loading conditions and microstructure analysis of this material.

Microstructure and Mechanical Properties of Spark-Plasma-Sintered SiC-TiC Composites

2005 ◽  
Vol 287 ◽  
pp. 335-339 ◽  
Author(s):  
Kyeong Sik Cho ◽  
Kwang Soon Lee
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Heating Rate ◽  
Spark Plasma Sintering ◽  
Sintering Temperature ◽  
Applied Pressure ◽  
Argon Atmosphere ◽  
Full Density ◽  
Plasma Sintering ◽  
Spark Plasma

Rapid densification of the SiC-10, 20, 30, 40wt% TiC powder with Al, B and C additives was carried out by spark plasma sintering (SPS). In the present SPS process, the heating rate and applied pressure were kept at 100°C/min and at 40 MPa, while the sintering temperature varied from 1600-1800°C in an argon atmosphere. The full density of SiC-TiC composites was achieved at a temperature above 1800°C by spark plasma sintering. The 3C phase of SiC in the composites was transformed to 6H and 4H by increasing the process temperature and the TiC content. By tailoring the microstructure of the spark-plasma-sintered SiC-TiC composites, their toughness could be maintained without a notable reduction in strength. The strength of 720 MPa and the fracture toughness of 6.3 MPa·m1/2 were obtained in the SiC-40wt% TiC composite prepared at 1800°C for 20 min.

Powder characterization and part density for powder bed fusion of 17-4 PH stainless steel

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Sean Daniel Dobson ◽  
Thomas Louis Starr
Keyword(s):  
Particle Size ◽  
Stainless Steel ◽  
Flow Behavior ◽  
Full Density ◽  
Powder Bed Fusion ◽  
Metal Powders ◽  
Production Environment ◽  
Content Type ◽  
Powder Bed ◽  
Part Density

Purpose Characteristics of the metal powder are a key factor in the success of powder bed fusion (PBF) additive manufacturing. Powders for PBF from different manufacturers may have a different particle size and/or bulk packing and flow behavior. Powder properties change as the powder is reused for multiple builds. This study seeks to measure the variability of commercial 17-4 PH stainless steel powders to determine the effect of powder variability on part density and demonstrate characterization methods that ensure part quality. Design/methodology/approach Commercial atomized metal powders from four different vendors were produced with two different atomizing gases (N2 and argon). Powder was characterized in both new and extensively reused conditions. All powders were characterized for flow and packing behavior, particle size and internal porosity. Coupons were manufactured using the laser PBF process with optimized scan strategy and exposure parameters. The quality of fabricated parts was measured using bulk density measurement. Findings Despite differences in powder flowability and particle size, fully dense parts (>99 per cent) were produced using all powders, except one. Residual porosity in these parts appeared to result from gas trapped in the powder particles. The powder with extensive reuse (400+ h in machine fabrication environment) exhibited reduced flowability and increased fraction of fine particles, but still produced full density parts. Originality/value This study demonstrates that full density parts can be fabricated using powders with a range of flowability and packing behavior. This suggests that a single flowability measurement may be sufficient for quality assurance in a production environment.

Comparative analysis of structure and hardness of cast and direct metal laser sintering produced Co-Cr alloys used for dental devices

2016 ◽  
Vol 22 (1) ◽  
pp. 144-151 ◽  
Author(s):  
Ana R. Lapcevic ◽  
Danimir P Jevremovic ◽  
Tatjana M Puskar ◽  
Robert J. Williams ◽  
Dominic Eggbeer
Keyword(s):  
Casting Machine ◽  
Hardness Test ◽  
Metallic Phase ◽  
Laser Sintering ◽  
Mean Value ◽  
Dental Alloy ◽  
Direct Metal Laser Sintering ◽  
Compact Structure ◽  
Content Type ◽  
Conventional Casting

Purpose – The purpose of this paper is to analyse structure and measure hardness of Co-Cr dental alloy samples made with two different technologies, conventional casting method (CCM samples) and additive direct metal laser sintering technology (DMLS samples), and to compare the results. Design/methodology/approach – CCM samples were made in a conventional casting machine, using remanium 800+ Co-Cr dental alloy (Dentaurum, Ispringen, Germany). DMLS samples were fabricated out of EOS CC SP2 Co-Cr alloy (EOS, GmbH, Munich, Germany) using DMLS technology. Samples for structural analysis were plate-shaped (10 × 10 × 1.5 mm3) and for the hardness test were prismatic-shaped (55 × 10.2 × 11.2 mm3). Structure was analysed via an inverting microscope and colour metallography method. Findings – CCM samples have a dense, irregular dendritic mesh, which is typical for the metallic phase of the Co-Cr dental alloy. DMLS alloy has a more homogenous and more compact structure, compared to CCM. Metals, the alloy basis consists of, form semilunar stratified layers, which are characteristic for the additive manufacturing (AM) technique. Hardness values of DMLS (mean value was 439.84 HV10) were found to be higher than those of CCM (mean value was 373.76 HV10). Originality/value – There are several reports about possible use of AM technologies for manufacturing dental devices, and investigation of mechanical properties and biocompatibility behaviour of AM-produced dental alloys. Microstructure of Co-Cr alloy made with DMLS technology has been introduced for the first time in the present paper.

Microstructure and Tensile Strength of Rapid Manufacturing Parts

2014 ◽  
Vol 903 ◽  
pp. 114-117 ◽  
Author(s):  
Izhar Abd Aziz ◽  
Brian Gabbitas ◽  
Mark Stanford
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Biomedical Applications ◽  
Bulk Material ◽  
Solidification Rate ◽  
Laser Sintering ◽  
Liquid Pool ◽  
Sintering Process ◽  
Direct Metal Laser Sintering ◽  
Production Route

The purpose of this work is to investigate the microstructure and tensile strength of Ti6Al4V pre-alloyed powders produced by a direct metal laser sintering technique. Traditionally, Ti6Al4V products for biomedical applications were produced through hot working or machining of wrought semi-finished products. A change in the production route for manufacturing Ti6Al4V products, from the more traditional methods to an additive manufacturing route, requires an investigation of microstructure and mechanical properties because these are strongly influenced by the production route. The microstructure obtained through rapid solidification during laser sintering shows a very fine α+β lamellar morphology. There is also evidence of martensite which was expected due to high solidification rate of the liquid pool from a temperature above the β-transus during the laser sintering process. Structurally, good mechanical properties which are comparable to the bulk material were obtained.

Fundamental investigation of part properties at accelerated beam speeds in the selective laser sintering process

2017 ◽  
Vol 23 (6) ◽  
pp. 1099-1106 ◽  
Author(s):  
Matthias Michael Lexow ◽  
Maximilian Drexler ◽  
Dietmar Drummer
Keyword(s):  
Mechanical Properties ◽  
Heating Rate ◽  
Energy Input ◽  
Selective Laser Sintering ◽  
Stable Process ◽  
Peak Height ◽  
Laser Sintering ◽  
Scanning Calorimetry ◽  
Content Type ◽  
The Core

Purpose Despite the recent progress in basic process understanding considering the selective laser sintering (SLS) of thermoplastics, several aspects of the mechanisms of the beam and powder interaction are not fully understood yet. Recent studies covered the correlation of mechanical properties and part density with the heating rate. The surface roughness of the test specimens was also considered but showed no distinct relation to the part mechanics. The purpose of this paper is to provide a new fundamental model for describing the decreasing mechanical properties with increasing beam speed. Design/methodology/approach While the dependence of mechanical properties with total energy input during exposure is well published, the correlation of the exposure speed with the degree of particle melt (DPM) is the subject of the present study. The DPM is accessible through differential scanning calorimetry measurements. Supporting the previously introduced method of the core-peak height, the interpretation via the core-peak area is proposed as a means to ascertain the melting behaviour for different processing conditions. Further support of the observations is given by x-ray computed tomography and microscopy which allows for a correlation with the respective porosity and inner structure of the parts. Findings The authors show a novel way of describing the decreasing mechanical properties with increasing speed of energy input by showing the dependence of the DPM on the heating rate during exposure. Practical implications The results offer an addition to the understanding considering the reliability and reproducibility of the SLS process. Originality/value The paper extends the existing models of the time-dependent material behaviour, which allows for the derivation of new efficient and stable process strategies.

Characterization and optimization of laser sintering copolyamide/polyether sulfone hot-melt adhesive mixtures

2019 ◽  
Vol 25 (3) ◽  
pp. 614-622
Author(s):  
Hui Zhang ◽  
Yanling Guo ◽  
Kaiyi Jiang ◽  
David Bourell ◽  
Jian Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Laser Energy ◽  
Laser Sintering ◽  
Polymer Mixture ◽  
Binding Mechanism ◽  
Content Type ◽  
Polyether Sulfone ◽  
Cent Increase ◽  
Mass Ratios ◽  
Hot Melt

PurposeA new kind of polymer mixture (co-PA-PES) was prepared in different mass ratios, by mixing polyether sulfone hot-melt adhesive (PES-HmA) and copolyamide B249 (PA-B249). This study aims to investigate its characteristics of laser sintering and get the optimal process parameters.Design/methodology/approachThe effect of mass ratio of co-PA-PES on thermal behavior was analyzed using a simultaneous thermal analyzer, and the density and mechanical properties of sintered parts were tested to evaluate the performance of the polymeric system. Scanning electron microscopy and Fourier transform infrared spectroscopy were performed to characterize the microstructure and binding mechanism of sintered co-PA-PES parts. Specifically, mechanical properties of the mixture with 20 Wt.% PA-B249 were optimized based on a design of experiment methodology, along with the restriction of maximum absorbable laser energy density.FindingsLiquid phase fusion was considered as the main sintering mechanism for co-PA-PES, and mechanical interlocking was the dominant binding mechanism. The effects of mass ratios of this material on the thermal properties, density and mechanical properties were obtained via data results. Additionally, compared to neat PES-HmA, co-20 Wt.% PA-PES showed a 71.7 per cent increase in tensile strength, 24.4 per cent increase in flexural strength and 102.1per cent increase in impact strength.Originality/valueThis paper proposed a new kind of polymer mixture as the feedstock for laser sintering with the advantages of low price and easy processing. The filler of PA-B249 effectively improved the performance of the polymer mixture, including but not limited to mechanical properties.

scholarly journals PRODUCTION OF PROTOTYPE PARTS USING DIRECT METAL LASER SINTERING TECHNOLOGY

2015 ◽  
Vol 55 (4) ◽  
pp. 260 ◽  
Author(s):  
Josef Sedlak ◽  
Oskar Zemčík ◽  
Martin Slaný ◽  
Josef Chladil ◽  
Karel Kouřil ◽  
...  
Keyword(s):  
Rapid Prototyping ◽  
Automotive Industry ◽  
Laser Sintering ◽  
Additive Technologies ◽  
Metal Powders ◽  
Direct Metal Laser Sintering ◽  
Direct Production ◽  
Unconventional Methods ◽  
Material Preparation ◽  
Economic Comparison

<p>Unconventional methods of modern materials preparation include additive technologies which involve the sintering of powders of different chemical composition, granularity, physical, chemical and other utility properties. The technology called Rapid Prototyping, which uses different technological principles of producing components, belongs to this type of material preparation. The Rapid Prototyping technology facilities use photopolymers, thermoplastics, specially treated paper or metal powders. The advantage is the direct production of metal parts from input data and the fact that there is no need for the production of special tools (moulds, press tools, etc.). Unused powder from sintering technologies is re-used for production 98% of the time, which means that the process is economical, as well as ecological.The present paper discusses the technology of Direct Metal Laser Sintering (DMLS), which falls into the group of additive technologies of Rapid Prototyping (RP). The major objective is a detailed description of DMLS, pointing out the benefits it offers and its application in practice. The practical part describes the production and provides an economic comparison of several prototype parts that were designed for testing in the automotive industry.</p>

A comparative study of knitted strain sensors fabricated with conductive composite and coated yarns

2019 ◽  
Vol 31 (2) ◽  
pp. 181-194 ◽  
Author(s):  
Rafiu King Raji ◽  
Xuhong Miao ◽  
Shu Zhang ◽  
Yutian Li ◽  
Ailan Wan ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Strain Sensor ◽  
Strain Sensors ◽  
Original Research ◽  
Conductive Composite ◽  
Content Type ◽  
Blended Yarn ◽  
Spun Yarn ◽  
Conductive Yarns

PurposeThe use of conductive yarns or wires to design and construct fabric-based strain sensors is a research area that is gaining much attention in recent years. This is based on a profound theory that conductive yarns will have a variation in resistance if subjected to tension. What is not clear is to which types of conductive yarns are most suited to delivering the right sensitivity. The purpose of this paper is to look at strain sensors knitted with conductive composite and coated yarns which include core spun, blended, coated and commingled yarns. The conductive components are stainless steel and silver coating respectively with polyester as the nonconductive part. Using Stoll CMS 530 flat knitting machine, five samples each were knitted with the mentioned yarn categories using 1×1 rib structure. Sensitivity tests were carried out on the samples. Piezoresistive response of the samples reveals that yarns with heterogeneous external structures showed both an increase and a decrease in resistance, whereas those with homogenous structures responded linearly to stress. Stainless steel based yarns also had higher piezoresistive range compared to the silver-coated ones. However, comparing all the knitted samples, silver-coated yarn (SCY) proved to be more suitable for strain sensor as its response to tension was unidirectional with an appreciable range of change in resistance.Design/methodology/approachConductive composite yarns, namely, core spun yarn (CSY1), core spun yarn (CSY2), silver-coated blended yarn (SCBY), staple fiber blended yarn (SFBY) and commingled yarn (CMY) were sourced based on specifications and used to knit strain sensor samples. Electro-mechanical properties were investigated by stretching on a fabric tensile machine to ascertain their suitability for a textile strain sensor.FindingsIn order to generate usable signal for a strain sensor for a conductive yarn, it must have persistent and consistent conductive links, both externally and internally. In the case of composite yarns such as SFBY, SCBY and CMY where there were no consistent alignment and inter-yarn contact, resistance change fluctuated. Among all six different types of yarns used, SCY presented the most suitable result as its response to tension was unidirectional with an appreciable range of change in resistance.Originality/valueThis is an original research carried out by the authors who studied the electro-mechanical properties of some composite conductive yarns that have not been studied before in textile strain sensor research. Detailed research methods, results and interpretation of the results have thus been presented.

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