Publikationer från Malmö universitet
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Microstructures and surface roughness of EBM produced Ti-6Al-4V
Malmö högskola, Teknik och samhälle (TS).
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 [en]
EBM, Ti-6Al-4V
HSV kategori
Identifikatorer
URN: urn:nbn:se:mau:diva-7791Lokal ID: 13130ISBN: 978-91-7473-063-0 (tryckt)OAI: oai:DiVA.org:mau-7791DiVA, id: diva2:1404732
Merknad

All papers in dissertation as manuscripts.

Tilgjengelig fra: 2020-02-28 Laget: 2020-02-28 Sist oppdatert: 2024-03-04bibliografisk kontrollert
Delarbeid
1. Evaluation of microstructural development in electron beam melted Ti-6Al-4V
Åpne denne publikasjonen i ny fane eller vindu >>Evaluation of microstructural development in electron beam melted Ti-6Al-4V
2012 (engelsk)Inngår i: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 65, s. 8-15Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

In the current work an investigation of the microstructures of EBM built Ti-6Al-4V test bars has been performed using OM, SEM, TEM and XRD. It has been found that the prior β phase, that formed during the initial solidification, possesses a column shaped morphology with growing direction parallel to built direction. Typical (α+β) structures namely Widmanstätten α platelets with rod-like β phase formed on the interfaces of the fine α grains, have been observed in the columnar prior β grains. Grain boundary α phase was found to be formed around the boundaries of the columnar prior β grains. Different phases present in the parts, especially the BCC β phases have been characterized. The TEM/EDX results indicate very high V composition in the β phase. Results of TEM/SAED and XRD also revealed that a superlattice structure could be present in the β phase. Phase transformation sequence is discussed according to the processing history and the microstructures observed.

sted, utgiver, år, opplag, sider
Elsevier, 2012
Emneord
Ti-6Al-4V, EBM, Microstructures, SEM, TEM, XRD
HSV kategori
Identifikatorer
urn:nbn:se:mau:diva-2510 (URN)10.1016/j.matchar.2011.12.008 (DOI)000302584200002 ()2-s2.0-84855869744 (Scopus ID)13321 (Lokal ID)13321 (Arkivnummer)13321 (OAI)
Tilgjengelig fra: 2020-02-27 Laget: 2020-02-27 Sist oppdatert: 2024-03-04bibliografisk kontrollert
2. Effect of process parameters settings and thickness on surface roughness of EBM produced Ti-6Al-4V
Åpne denne publikasjonen i ny fane eller vindu >>Effect of process parameters settings and thickness on surface roughness of EBM produced Ti-6Al-4V
Vise andre…
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
Emneord
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:nbn:se:mau:diva-2723 (URN)10.1108/13552541211250391 (DOI)000308835800007 ()2-s2.0-84864269123 (Scopus ID)15797 (Lokal ID)15797 (Arkivnummer)15797 (OAI)
Tilgjengelig fra: 2020-02-27 Laget: 2020-02-27 Sist oppdatert: 2024-03-04bibliografisk kontrollert
3. Effect of Process Parameter Settings and Thickness on Microstructures of EBM Produced TI-6Al-4V Alloy: [工艺参数设置和厚度对电子束熔融加工Ti-6Al-4V合金微观结构的影响]
Åpne denne publikasjonen i ny fane eller vindu >>Effect of Process Parameter Settings and Thickness on Microstructures of EBM Produced TI-6Al-4V Alloy: [工艺参数设置和厚度对电子束熔融加工Ti-6Al-4V合金微观结构的影响]
2021 (engelsk)Inngår i: Xiyou jinshu cailiao yu gongcheng, ISSN 1002-185X, Vol. 50, nr 2, s. 408-415Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The effect of sample dimensions and process parameters (beam current, scan speed, offset focus and scan length) of electron beam melting (EBM) system on microstructure of the EBM built Ti-6Al-4V alloy was investigated. The microstructure of EBM built Ti-6Al-4V alloy consists of columnar grains of prior β phase. Inside the columnar grain, typical (α+β) structures, namely Widmanstätten α platelets and rod-like β phase formed on the interfaces of the fine α grains, are observed. Grain boundary α layer forms along grain boundary of prior β columnar grain. With the increase of thickness of the test slab, beam energy density and scanning length, the prior β columnar grain grows along the build direction and diameter of which increases. The columnar grain diameter also decreases with the increase in height of the test slab. With increasing the thickness of the test slab and beam energy density, α platelets get coarser. 

Abstract [zh]

本文研究了试件尺寸和工艺参数(电子束强度,扫描速度,焦点偏移量和扫描长度)对EBM加工的Ti-6Al-4V微观结构的影响。通常,可以观察到EBM加工的Ti-6Al-4V的微观结构是由原始β相的柱状晶粒组成。在柱状晶粒内部观察到典型的(α+β)结构,即魏氏体α片和在细小的α晶粒的界面上形成的杆状β相。还发现沿原始β柱状晶粒的晶界形成α层晶界。随着试件厚度,电子束能量密度和扫描长度的增加,先前的β柱状晶粒的直径增大,并且生长的方向与加工方向一致。同时,柱状晶粒直径也随着高度的增加而减小。随着厚度和电子束能量密度的增加,α片会变得更粗大。

sted, utgiver, år, opplag, sider
Science Press, 2021
Emneord
Ti-6Al-4V, EBM, process parameters, Ti-6Al-4V,电子束熔融,工艺参数
HSV kategori
Identifikatorer
urn:nbn:se:mau:diva-56873 (URN)000635253000005 ()
Tilgjengelig fra: 2022-12-21 Laget: 2022-12-21 Sist oppdatert: 2024-03-04bibliografisk kontrollert

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