Critical role of scan strategies on the development of microstructure, texture, and residual stresses during laser powder bed fusion additive manufacturing

Nadammal, Naresh; Mishurova, Tatiana; Fritsch, Tobias; Serrano-Muñoz, Itziar; Kromm, Arne; Haberland, Christoph; Portella, Pedro Dolabella; Bruno, Giovanni

doi:10.1016/j.addma.2020.101792

Cited by 82 publications

(51 citation statements)

References 55 publications

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“…[7][8][9][10][11] Literature works have also shown the potential of AM to tailor the material grain structure and texture, for instance, by altering the path that the heat source follows during selective melting (namely, the scan strategy). [12][13][14][15][16] This is because the solidification texture depends on competitive grain growth in one of the six <100> preferred growth directions in face-centered cubic alloys, as well as on the local heat flow direction. [17] Furthermore, different grain morphologies (i.e., columnar, where a grain can expand over several subsequent layers, or equiaxed) can be obtained by controlling the thermal gradient (G, K m À1 ) and the solidification rate (R, m s À1 ).…”

Section: Introductionmentioning

confidence: 99%

Scanning Manufacturing Parameters Determining the Residual Stress State in LPBF IN718 Small Parts

et al. 2021

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The influence of scan strategy on the residual stress (RS) state of an as-built IN718 alloy produced by means of laser powder bed fusion (LPBF) is investigated. Two scan vector rotations (90 -alternation and 67 -rotation), each produced following two different scan vector lengths (long and short), are used to manufacture four rectangular prisms. Neutron diffraction (ND) and laboratory X-ray diffraction (XRD) techniques are used to map the bulk and surface RS state, respectively. The distortion induced upon removal from the baseplate is measured via profilometry. XRD measurements show that the two long scan vector strategies lead to higher RS when compared with the equivalent short scan vector strategies. Also, the 67 -rotation strategies generate lower RS than their 90 -alternation counterparts. Due to the lack of reliable stress-free d 0 references, the ND results are analyzed using von Mises stress. In general, ND results show significant RS spatial non-uniformity. A comparison between ND and distortion results indicates that the RS component parallel to the building direction (Z-axis) has a predominant role in the Z-displacement. The use of a stress balance scheme allows to discuss the d 0 variability along the length of the specimens, as well as examine the absolute RS state.

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Section: Introductionmentioning

confidence: 99%

Scanning Manufacturing Parameters Determining the Residual Stress State in LPBF IN718 Small Parts

et al. 2021

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“…processing parameters (e.g. scanning speed (Kuo et al 2020;Huang et al 2021), hatch distance (Kuo et al 2020), and laser power (Huang et al 2021), optimising scanning strategies (Nadammal et al 2021;Sing and Yeong 2020), and using a top-hat laser profile (Huang et al 2021)). If the melting points of the two materials are similar, the above measures are suitable for suppressing the occurrence of defects due to the lack of fusion.…”

Section: Lack Of Fusion and Element Segregationmentioning

confidence: 99%

Recent progress and scientific challenges in multi-material additive manufacturing via laser-based powder bed fusion

Wei¹,

Li²

2021

Virtual and Physical Prototyping

137

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Multi-material additive manufacturing provides a new route for fabricating components with tailored physical properties. Laser-based powder bed fusion (L-PBF), also known as selective laser melting, is a powder bed-based additive manufacturing technology. This technology affords the advantage of manufacturing metallic and non-metallic materials with high geometrical resolution. An emerging field relevant to the foregoing is multi-material L-PBF. This paper reviews the latest progress in this field including multiple material powder deposition mechanisms, molten pool behaviour, process characteristics of printing metal-metal, metal-ceramic, and metal-polymer multiple material components, and potential applications. Finally, scientific and technological challenges are presented.

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“…[ 17 ] Here and in other studies, it was found that the strength and ductility are increased by a rotation of 90° in subsequent layers compared to unidirectional scanning. [ 18 ] These studies further revealed that rotational scanning can effectively reduce the tensile stresses at the top surface. Reduced stress by alternated scanning was found in other studies as well.…”

Section: Introductionmentioning

confidence: 97%

A Novel Approach to Robustly Determine Residual Stress in Additively Manufactured Microstructures Using Synchrotron Radiation

et al. 2021

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Introduction 1.1. Microstructure of Additively Manufactured MaterialsAdditive manufacturing (AM) is the subject of many recent publications. [1][2][3] Typical representatives of AM methods for the processing of metallic metals are mainly divided into three categories: wire feeding, powder feeding, and powder bed fusion systems. [3] The latter technique enables the production of metallic structures by layer-wise melting of a thin metal powder bed only using AM equipment and a sliced model generated by a computeraided design (CAD) program. The application of a powder bed in powder-based AM technology facilitates the selective processing of individual layers in complex geometry. The most commonly used powder bed fusion techniques are selective electron beam powder bed fusion (EPBF) and laser powder bed fusion (LPBF). [3,4] EPBF structures are produced in a vacuum atmosphere and at a high temperature, eventually leading to a relatively low residual stress level. In contrast, LPBF processes usually take place at temperatures up to 200 C. The localized energy input and the small melt pool sizes, respectively, in combination with low build chamber temperatures result in high temperature gradients, whereby residual stresses are favored. [5] Generally, the influence of scan vectors and related strategies is a complex topic, which crucially has to be dealt with. Scan vector lengths, orientations, the order of rotation within a specific layer, and its subsequent layers are variables in every building process. Only a very limited number of comprehensive studies have reported on the effect of the scan strategy on the density, microstructure, mechanical properties, and residual stresses of LPBF parts, as clearly stated in previous studies. [5][6][7][8] Already an increased scan path length, e.g., due to a change of cross-section of a part, can result in a severely decreased relative density as well as fundamentally changed microstructure. [9,10] The influence of parameters on the evolution of residual stresses was already numerously studied. [11,12] The authors showed that the residual stresses are mainly influenced by cooling rates, temperature gradients, and melt pool sizes. Also, a minimization of the temperature gradient by powder bed preheating is an option to reduce process-induced stresses. [1,13] The high influence of the laser power and the effect of scan strategies have been characterized.

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Critical role of scan strategies on the development of microstructure, texture, and residual stresses during laser powder bed fusion additive manufacturing

Cited by 82 publications

References 55 publications

Scanning Manufacturing Parameters Determining the Residual Stress State in LPBF IN718 Small Parts

Scanning Manufacturing Parameters Determining the Residual Stress State in LPBF IN718 Small Parts

Recent progress and scientific challenges in multi-material additive manufacturing via laser-based powder bed fusion

A Novel Approach to Robustly Determine Residual Stress in Additively Manufactured Microstructures Using Synchrotron Radiation

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