Thermal Decomposition of Massive Phase to Fine Lamellar α/β in Ti–6Al–4V Additively Manufactured Alloy by Directed Energy Deposition

Suprobo, Ghozali; Ammar, Abdul Azis; Park, Nokeun; Baek, Eung Ryul; Kim, Sung-Wook

doi:10.1007/s12540-019-00304-4

Cited by 32 publications

(13 citation statements)

References 31 publications

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“…As for the α m observation, the α m in the top layer exhibits a sub-lamellar structure (Figs. 3a-3c), which is similar to the previous study 11) . In the middle layer, the morphology of α m exhibits a more continuous lamellar structure Fig.…”

Section: Resultssupporting

confidence: 91%

“…In DED Ti-6Al-4V, the microstructures of α' martensite and α massive phase (α m ) are generally formed due to the high cooling rate introduced during the process 10) . The α' and α m usually are observed with the appearance of acicular and sub-lamellar morphology, respectively 11) . However, the microstructures of α' and α m in the lower layer experience intrinsic heat treatment due to the repetition of subsequent layers during building the product 12,13) .…”

Section: Introductionmentioning

confidence: 99%

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The Effect of Decomposed Microstructure on Mechanical Properties of Additively Manufactured Ti-6Al-4V Alloy

Nursyifaulkhair

Park

Baek

2021

Journal of Welding and Joining

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This study investigated the effect of microstructural decomposition on the mechanical properties of additively manufactured Ti-6Al-4V by directed energy deposition. The formation of ' martensite and massive phase ( m ) was observed in the deposited layers. The ' and m in the lastly deposited layer appeared as a needle-shaped and a sub-lamellar structure, respectively. However, the morphology of ' and m was decomposed in the lower layers due to the intrinsic heat treatment. Moreover, The heat conduction rate calculation showed that the lower powder feed rate generates more heat conduction. Therefore, the microstructure was further decomposed for the specimen with a lower powder feed rate. These phenomena consequently affected the mechanical properties and fracture behavior of the Ti-6Al-4V alloy.

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Section: Resultssupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

The Effect of Decomposed Microstructure on Mechanical Properties of Additively Manufactured Ti-6Al-4V Alloy

Nursyifaulkhair

Park

Baek

2021

Journal of Welding and Joining

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“…In titanium alloys, martensite formation is strictly dependent on the cooling rate that the sample undergoes, if the initial temperature is above T β (β transition temperature), approximately 995 °C [17] for Ti-6Al-4V. During deposition, the cooling rate is high enough to allow martensite formation [38], although the dimension of the α' needles is again strictly dependent on several conditions, most importantly cooling rate [37,39]. This value is directly correlated to the energy density used during the process.…”

Section: Resultsmentioning

confidence: 99%

Single Scans of Ti-6Al-4V by Directed Energy Deposition: A Cost and Time Effective Methodology to Assess the Proper Process Window

et al. 2021

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Directed energy deposition is an additive manufacturing technology which usually relies on prototype machines or hybrid systems, assembled with parts from different producers. Because of this lack of standardization, the optimization of the process parameters is often a mandatory step in order to develop an efficient building process. Although, this preliminary phase is usually expensive both in terms of time and cost. The single scan approach allows to drastically reduce deposition time and material usage, as in fact only a stripe per parameters combination is deposited. These specimens can then be investigated, for example in terms of geometrical features (e.g. growth, width) and microstructure to assess the most suitable process window. In this work, Ti-6Al-4V single scans, produced by means of directed energy deposition, corresponding to a total of 50 different parameters combinations, were analyzed, focusing on several geometrical features and relative parameters correlations. Moreover, considering the susceptibility of the material to oxygen pick-up, the necessity of an additional shielding gas system was also evaluated, by comparing the specimens obtained with and without using a supplementary argon flow. A process window, which varies according to the user needs, was found together with a relationship between microstructure and process parameters, in both shielding scenarios. Graphic Abstract

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“…Through analysis, it is considered that the reason for the EBW joint fracturing in the WM under HCF may be related to more acicular martensite α′ phases contained in the WM. Some studies 25,26 show that acicular α′ phases, as the strengthening phases in Ti alloy, can reduce ductility of materials while improving the microhardness of the WM. The reduction of ductility implies that when the materials resist the external load, it is difficult to deform and the internal dislocations are easy to pile up, which can lead to local stress concentration, thus crack initiating.…”

Section: Discussionmentioning

confidence: 99%

Comparison of fatigue performance of TC4 titanium alloy welded by electron beam welding and laser welding with filler wire

Long

Zhang

Zhang³

et al. 2022

Fatigue Fract Eng Mat Struct

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This research compared high‐cycle fatigue (HCF) performances of joints of Ti–6Al–4V titanium (TC4) alloy with the thickness of 30 mm welded by vacuum electron beam welding (EBW) and laser welding with filler wire (LWFW) (hereinafter referred to as EBW and LWFW joints). Under test conditions, the fatigue strength of the LWFW joint is only 65% that of the EBW joint. Based on analysis, the main reason is that a larger microhardness gradient is present in the LWFW joint. The average microhardness of the weld metal (WM) of the LWFW joint is 41 HV lower than that of base metal (BM). A lot of punctate β phases in the WM of the LWFW joint may be an important reason for its softening. The research results provide data supports for the application of the EBW and LWFW of Ti alloy in the field of aviation manufacturing.

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Thermal Decomposition of Massive Phase to Fine Lamellar α/β in Ti–6Al–4V Additively Manufactured Alloy by Directed Energy Deposition

Cited by 32 publications

References 31 publications

The Effect of Decomposed Microstructure on Mechanical Properties of Additively Manufactured Ti-6Al-4V Alloy

The Effect of Decomposed Microstructure on Mechanical Properties of Additively Manufactured Ti-6Al-4V Alloy

Single Scans of Ti-6Al-4V by Directed Energy Deposition: A Cost and Time Effective Methodology to Assess the Proper Process Window

Comparison of fatigue performance of TC4 titanium alloy welded by electron beam welding and laser welding with filler wire

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