Effect of AM-induced Anisotropy on the Surface Integrity of Laser Powder Bed Fused Ti6Al4V Machined Parts

Lizzul, Lucia; Bertolini, Rachele; Ghiotti, Andrea; Bruschi, Stefania

doi:10.1016/j.promfg.2020.04.149

Cited by 11 publications

(4 citation statements)

References 13 publications

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“…Due to the naturally high anisotropy of AM components, the investigation of the microstructural anisotropy is an essential necessity in order to finally classify and evaluate the results obtained in this study. Lizzul et al have shown, for example, that the microstructural anisotropy of AM components has an influence on the resulting surface integrity of the subsequent machining process [21]. Furthermore, an enormous additive manufacturing-induced anisotropy of the tool wear was shown [22], which is why it can be assumed that the cutting force also shows a strong additive manufacturing-induced anisotropy when machining AM components.…”

Section: Discussionmentioning

confidence: 99%

Optimisation of surface residual stresses using ultrasonic-assisted milling for wire-arc additive manufactured Ni alloy components

Engelking

Eissel

Schroepfer

et al. 2023

Int J Adv Manuf Technol

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Nickel alloys are cost intensive materials and generally classified as difficult-to-cut material. However, machining of these materials is needed especially in case of alloy 36 (1.3912), which is commonly used in mould construction for the production of fibre-reinforced composites. With regard to repair, modification and manufacturing of such components, additive manufacturing offers significant economic advantages. Nevertheless, subsequent machining steps are needed to achieve the final component contour and defined surface conditions. Dependent on the material and machining process conditions, detrimental tensile residual stresses may be the result on the machined surface, having negative impact on the component performance and safety. In this investigation, machining experiments were carried out on wire arc additive manufactured components made of alloy 36, varying the cutting speed and the feed rate. In addition, the conventional milling process (CM) was compared with a modern, hybrid machining process, the ultrasonic-assisted milling (US). The cutting forces and the surface-near residual stresses were analysed using X-ray diffraction. A significant improvement of the machinability as well as the surface integrity by using the ultrasonic assistance was observed, especially at low cutting speeds. The CM induced mainly tensile residual stresses, the US mainly compressive residual stresses.

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Section: Discussionmentioning

confidence: 99%

Optimisation of surface residual stresses using ultrasonic-assisted milling for wire-arc additive manufactured Ni alloy components

Engelking

Eissel

Schroepfer

et al. 2023

Int J Adv Manuf Technol

View full text Add to dashboard Cite

show abstract

“…Compared with wrought parts, the surface quality of as-built additively manufactured parts is poor. Lizzul et al [ 103 ] investigated the influence of microstructure on the surface integrity of additively manufactured Ti-6Al-4V fabricated by PBF-LB. According to the analysis of AM-induced microstructure, the material structure, including the α phase layer and the β grains, have a significant effect on the surface roughness of the samples.…”

Section: Machinability Of Additively Manufactured Ti-6al-4vmentioning

confidence: 99%

“… Microstructure along the build-up direction of the PBF-LB Ti-6Al-4V. The red arrows show the α-phase layers along the prior β grains boundaries [ 103 ] (Reprinted with permission from [ 103 ]. Copyright 2020, Elsevier).…”

Section: Figurementioning

confidence: 99%

The State of the Art in Machining Additively Manufactured Titanium Alloy Ti-6Al-4V

et al. 2023

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Titanium alloys are extensively used in various industries due to their excellent corrosion resistance and outstanding mechanical properties. However, titanium alloys are difficult to machine due to their low thermal conductivity and high chemical reactivity with tool materials. In recent years, there has been increasing interest in the use of titanium components produced by additive manufacturing (AM) for a range of high-value applications in aerospace, biomedical, and automotive industries. The machining of additively manufactured titanium alloys presents additional machining challenges as the alloys exhibit unique properties compared to their wrought counterparts, including increased anisotropy, strength, and hardness. The associated higher cutting forces, higher temperatures, accelerated tool wear, and decreased machinability lead to an expensive and unsustainable machining process. The challenges in machining additively manufactured titanium alloys are not comprehensively documented in the literature, and this paper aims to address this limitation. A review is presented on the machining characteristics of titanium alloys produced by different AM techniques, focusing on the effects of anisotropy, porosity, and post-processing treatment of additively manufactured Ti-6Al-4V, the most commonly used AM titanium alloy. The mechanisms resulting in different machining performance and quality are analysed, including the influence of a hybrid manufacturing approach combining AM with conventional methods. Based on the review of the latest developments, a future outlook for machining additively manufactured titanium alloys is presented.

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“…In addition, also for Ti-6Al-4 V and L-PBF, Lizzul et al investigated the effect of AM-induced microstructure on the surface integrity by varying the scanning strategy and subsequent turning of the AM-components. They found that the scanning strategy has a significant influence on the microstructure, which in reverse influences the surface integrity due to machining [18]. Note that a sufficient surface integrity is a central requirement for highly stressed safety-relevant components.…”

Section: Introductionmentioning

confidence: 99%

Modification of Co–Cr alloys to optimize additively welded microstructures and subsequent surface finishing

et al. 2022

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Cobalt chromium alloys are often used in turbine and plant construction. This is based on their high thermal and mechanical stress resistance as well as their high wear resistance to corrosive and abrasive loads. However, cobalt is a cost-intensive material that is difficult to machine. Moreover, increasingly complex structures and the optimisation of resource efficiency also require additive manufacturing steps for the production or repair of components in many sectors. Concerning inhomogeneity and anisotropy of the microstructure and properties as well as manufacturing-related stresses, a lot of knowledge is still necessary for the economic use of additive welding processes in SMEs. As a result of the high stresses on the components and requirements for a high surface quality, a complementary use of additive and machining manufacturing processes is necessary. Thereby, Co–Cr alloys are extremely challenging for machining with geometrically defined cutting edges because of their low thermal conductivity combined with high strength and toughness. An approach to solve this problem is to refine and homogenise the microstructure. This is achieved by modifying the alloy with elements zirconium and hafnium, which are added up to a maximum of 1 wt.-%. A reduction of the process forces and stresses on the tool and work piece surface is also achievable via hybrid milling processes. There are already studies on the combined use of additive and machining manufacturing processes based on laser technology. However, knowledge based on powder and wire-based arc processes is important, as these processes are more widespread. Furthermore, the effects on the surface zone of additively manufactured components by hybrid finish milling have not yet been a subject of research. The results show that the structural morphology could be significantly influenced with the addition of zirconium and hafnium.

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Effect of AM-induced Anisotropy on the Surface Integrity of Laser Powder Bed Fused Ti6Al4V Machined Parts

Cited by 11 publications

References 13 publications

Optimisation of surface residual stresses using ultrasonic-assisted milling for wire-arc additive manufactured Ni alloy components

Optimisation of surface residual stresses using ultrasonic-assisted milling for wire-arc additive manufactured Ni alloy components

The State of the Art in Machining Additively Manufactured Titanium Alloy Ti-6Al-4V

Modification of Co–Cr alloys to optimize additively welded microstructures and subsequent surface finishing

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