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Effect of process parameters settings and thickness on surface roughness of EBM produced Ti-6Al-4V
Malmö högskola, Teknik och samhälle (TS).
Malmö högskola, Teknik och samhälle (TS).
Malmö högskola, Teknik och samhälle (TS).
Vise andre og tillknytning
2012 (engelsk)Inngår i: Rapid prototyping journal, ISSN 1355-2546, E-ISSN 1758-7670, Vol. 18, nr 5, s. 401-408Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Purpose – Ti-6Al-4V is one of the most attractive materials being used in aerospace, automotive and medical implant industries. Electron beam melting (EBM) is one of the direct digital manufacturing methods to produce complex geometries of fully dense and near net shape parts. The EBM system provides an opportunity to built metallic objects with different processing parameter settings like beam current, scan speed, probe size on powder, etc. The purpose of this paper is to determine and understand the effect of part's thickness and variation in process parameter settings of the EBM system on surface roughness/topography of EBM fabricated Ti-6Al-4V metallic parts. Design/methodology/approach – A mathematical model based upon response surface methodology (RSM) is developed to study the variation of surface roughness with changing process parameter settings. Surface roughness of the test slabs produced with different parameter settings and thickness has been studied under confocal microscope. Response surface methodology was used to develop a multiple regression model to correlate the effect of variation in EBM process parameters settings and thickness of parts on surface roughness of EBM produced Ti-6Al-4V. Findings – It has been observed that every part produced by EBM system has detectable surface roughness. The surface roughness parameter Ra varies between 1-20 µm for different samples depending upon the process parameter setting and thickness. The Ra value increases with increasing sample thickness and beam current, and decreases with increase in offset focus and scan speed. Originality/value – Surface roughness is related to wear and friction property of the material and hence is related to the life time and performance of the part. Surface roughness is an important property of any material to be considered as biomaterial. The surface roughness of the material depends upon the manufacturing method and environment and hence it is controllable either during fabrication or by post processing. From the 1st order regression model developed in this study, it is also evident that sample thickness, scan speed and beam current have relatively more effect on roughness value then the offset focus. With the model obtained equation, a designer can subsequently select the best combination of sample thickness and process parameter values to achieve desired surface roughness.

sted, utgiver, år, opplag, sider
Emerald Group Publishing Limited, 2012. Vol. 18, nr 5, s. 401-408
Emneord [en]
Alloys, Confocal microscope, Electron beam melting, Manufacturing systems, Multiple regression model, Ra, Response surface methodology, Surface roughness measurement, Ti-6Al-4V, Titanium
HSV kategori
Identifikatorer
URN: urn:nbn:se:mau:diva-2723DOI: 10.1108/13552541211250391ISI: 000308835800007Scopus ID: 2-s2.0-84864269123Lokal ID: 15797OAI: oai:DiVA.org:mau-2723DiVA, id: diva2:1399486
Tilgjengelig fra: 2020-02-27 Laget: 2020-02-27 Sist oppdatert: 2024-03-04bibliografisk kontrollert
Inngår i avhandling
1. Microstructures and surface roughness of EBM produced Ti-6Al-4V
Åpne denne publikasjonen i ny fane eller vindu >>Microstructures and surface roughness of EBM produced Ti-6Al-4V
2010 (engelsk)Licentiatavhandling, med artikler (Annet vitenskapelig)
Abstract [en]

The work presented in this dissertation is concerned with the microstructures andsurface roughness of test slabs of Ti-6Al-4V produced by one of powder based AdditiveManufacturing (AM) technique namely Electron Beam melting (EBM). The effects of processparameters of a EBM system and geometry factors of a EBM build such as slabs’ thickness andheight etc. on the microstructure and the surface roughness of the EBM produced Ti-6Al-4Vhave being investigated. The processing parameters of the EBM system involved in the presentwork include beam current, scan speed, offset focus and scanning length etc. In this study threedifferent batches of samples were prepared. Microstructures of EBM built Ti-6Al-4V werestudied using Optical Microscopy (OM), Scanning Electron Microscopy (SEM), TransmissionElectron Microscopy (TEM), and X-ray diffraction (XRD). Confocal microscopy and imageanalysis codes ImageJ’s routine SurfCharJ were used to quantify the surface roughness of the testslabs. The microstructures of EBM built Ti-6Al-4V in general consist of columnar grains of priorβ phase. Inside the columnar grains there is a typical (α+β) microstructure of titanium alloyscontaining Widmanstätten α platelets and rod-shaped β phase. Grain boundary α layer has alsobeen observed on the grain boundaries of prior b columnar grains. By using TEM, the β phase inEBM built Ti-6Al-4V has been identified as a rod-like structure located on the grain boundariesof the fine a grains and often grows up along the build direction. The size of the β rods is about200nm and the distance between the β rods is ranged between 0.5 -2μm. Chemical compositionsfor different phases have been measured by TEM/EDX and volume fraction of the β phase in theEBM Ti-6Al-4V has been determined to be 2.7%. The phase transformation sequence in EBMbuilt Ti-6Al-4V has been discussed according to processing history and microstructuresobserved. It has been observed that, the size, number and geometry of prior β columnar graindepend on the sample thickness and other process parameters setting. The diameter of columnargrain varies between 2-70μm. The increase in size, number and regularity of columnar grains hasbeen observed with increase in sample thickness, beam energy density and scanning length.While with increase in height of the build it decreases. The length and smoothness of α plateletsincreases with increase in diameter of prior β columnar grain. The β phase rods are unaffected bysample thickness and process parameter settings. The sample thickness and beam energy densityhas a strong effect on the surface roughness of the test slabs. The value of surface roughnesscoefficient Ra for different test slabs varies between 1-20μm. It is observed that the surfaceroughness increases of the test slab increases with increase in thickness of the slab and beamenergy density. The possible reasons for these variations in microstructures and surfaceroughness have been discussed.

sted, utgiver, år, opplag, sider
Solid Mechanics, Lund University, 2010. s. 71
Emneord
EBM, Ti-6Al-4V
HSV kategori
Identifikatorer
urn:nbn:se:mau:diva-7791 (URN)13130 (Lokal ID)978-91-7473-063-0 (ISBN)13130 (Arkivnummer)13130 (OAI)
Merknad

All papers in dissertation as manuscripts.

Tilgjengelig fra: 2020-02-28 Laget: 2020-02-28 Sist oppdatert: 2024-03-04bibliografisk kontrollert

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