The Influence of As-Built Surface Conditions on Mechanical Properties of Ti-6Al-4V Additively Manufactured by Selective Electron Beam Melting

Sun, Yu; Gulizia, Stefan; Oh, C. H.; Fraser, Darren; Leary, Martin; Yang, Yugui; Qian, Ma

doi:10.1007/s11837-015-1768-y

Cited by 103 publications

(36 citation statements)

References 16 publications

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“…In spite of the decreased ductility, the strength has a small increase relative to machined samples as shown in Fig. 7, which is opposite to previous studies [25] . The increased strength induced by surface roughness may be ascribed to the increased cross-sectional area due to the bonded powder particles.…”

Section: Vol15 No4 July 2018contrasting

confidence: 90%

Tensile behavior of Ti-6Al-4V alloy fabricated by selective laser melting: effects of microstructures and as-built surface quality

Pan

Huang

et al. 2018

China Foundry

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T i-6Al-4V is a typical α+β duplex-phase titanium alloy with outstanding specific strength, corrosion resistance and bio-compatibility, which has been widely applied in biomedical, aerospace, automotive, energy, chemical, and other industries [1] . However, the poor machinability and high cost of Ti-6Al-4V using a traditional processing route limit its more extensive application. Furthermore, the production of titanium alloy by conventional processing technology leads to Abstract: Selective laser melting (SLM) is a powerful additive manufacturing (AM) technology, of which the most prominent advantage is the ability to produce components with a complex geometry. The service performances of the SLM-processed components depend on the microstructure and surface quality. In this work, the microstructures, mechanical properties, and fracture behaviors of SLM-processed Ti-6Al-4V alloy under machined and as-built surfaces after annealing treatments and hot isostatic pressing (HIP) were investigated. The microstructures were analyzed by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscopy (TEM). The mechanical properties were measured by tensile testing at room temperature. The results indicate that the as-deposited microstructures are characterized by columnar grains and fi ne brittle martensite and the asdeposited properties present high strength, low ductility and obvious anisotropy. After annealing at 800-900°C for 2-4 h and HIP at 920°C/100MPa for 2 h, the brittle martensite could be transformed into ductile lamellar (α+β) microstructure and the static tensile properties of SLM-processed Ti-6Al-4V alloys in the machined condition could be comparable to that of wrought materials. Even after HIP treatment, the as-built surfaces could decrease the ductility and reduction of area of SLM-processed Ti-6Al-4V alloys to 9.2% and 20%, respectively. The crack initiation could occur at the columnar grain boundaries or at the as-built surfaces. The lamellar (α+β) microstructures and columnar grains could hinder or distort the crack propagation path during tensile tests.

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Section: Vol15 No4 July 2018contrasting

confidence: 90%

Tensile behavior of Ti-6Al-4V alloy fabricated by selective laser melting: effects of microstructures and as-built surface quality

Pan

Huang

et al. 2018

China Foundry

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“…The tensile properties of AM Ti-6Al-4V previously discussed were obtained from either machined (average roughness R a ≈ 1 μ m) or polished ( R a ≈ 0.1-0.5 μ m) samples. 54 Consequently, as-built AM Ti-6Al-4V specimens show noticeably lower tensile strengths and ductility, irrespective of the AM process, 19 , 54 -58 as microcracks were found to directly initiate from surface defects. 54 , 57 Acid etching, surface polishing, and machining have all proved to be effective in improving the surface roughness and therefore the mechanical properties.…”

Section: Eff Ects Of As-built Surface Conditionsmentioning

confidence: 94%

Additive manufacturing and postprocessing of Ti-6Al-4V for superior mechanical properties

et al. 2016

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“…Those challenges include poor surface finishing [6][7][8], porosity [9,10] and residual stresses [11]. In order to tackle these issues, post-treatments are usually applied to the near-net shape parts, such as machining or chemical etching to improve the surface finish [8,[12][13][14], Hot Isostatic Pressing (HIP) to increase the relative density [6,9,10,15] and improve the fatigue properties, or stress-relief [16]. The fully martensitic microstructure and high residual stresses observed in as-built SLM parts are very detrimental in terms of ductility [17,18].…”

Section: Introductionmentioning

confidence: 99%

Micromechanical behavior and thermal stability of a dual-phase α+α’ titanium alloy produced by additive manufacturing

et al. 2019

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In order to improve the tensile properties of additively manufactured Ti 6Al 4V parts, specific heat treatments have been developed. Previous work demonstrated that a sub-transus thermal treatment at 920°C followed by water quenching generates a dual-phase α+α′ microstructure with a high work-hardening capacity inducing a desirable increase in both strength and ductility. The present study investigates the micromechanical behavior of this α+α′ material as well as the thermal stability of the metastable α' martensite. To that end, annealing of the α+α′ microstructure is performed and the resulting microstructural evolution is analyzed, along with its impact on the tensile properties. A deeper understanding of the micromechanics of the multiphase microstructure both before and after annealing is achieved by performing in-situ tensile testing within a SEM, together with digital image correlation for full-field local strain measurements. This approach allows the strain partitioning to be quantified at a microscale and highlights a significant mechanical contrast between the two phases. In the α+α′ microstructure, the α′ phase is softer than the α phase, which is confirmed by nanoindentation measurements. Partial decomposition of the martensite during annealing induces a substantial hardening of the α′ phase, which is attributed to fine-scale precipitation and solution strengthening. A scale transition model based on the iso-work assumption and describing the macroscopic tensile behavior of the material depending on the individual mechanical behavior of each phase is also proposed. This model enables to provide insights into the underlying deformation and work-hardening mechanisms.

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The Influence of As-Built Surface Conditions on Mechanical Properties of Ti-6Al-4V Additively Manufactured by Selective Electron Beam Melting

Cited by 103 publications

References 16 publications

Tensile behavior of Ti-6Al-4V alloy fabricated by selective laser melting: effects of microstructures and as-built surface quality

Tensile behavior of Ti-6Al-4V alloy fabricated by selective laser melting: effects of microstructures and as-built surface quality

Additive manufacturing and postprocessing of Ti-6Al-4V for superior mechanical properties

Micromechanical behavior and thermal stability of a dual-phase α+α’ titanium alloy produced by additive manufacturing

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