Focus shift analysis, to manufacture dense and crack-free SLM-processed CM247LC samples

Gerstgrasser, Marcel; Cloots, Michael; Stirnimann, Josef; Wegener, Konrad

doi:10.1016/j.jmatprotec.2020.116948

Cited by 33 publications

(20 citation statements)

References 18 publications

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“…They tend to have a more "chaotic" morphology, compared to the classical solidification or hot cracks, as shown in Fig. 11 and analyzed in [24]. Furthermore, a new kind of defect is identified, which cannot be classified as a typical pore, due to its morphology, as shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Reaching a lower stress σ S2 in Fig. 11 Classical hot crack (solidification crack) from a sample with an increased laser beam diameter of approximately 116 μm, which leads to hot cracking, as explained in detail in [24] Fig. 12 New kind of defect, which has a different morphology, compared to a classical pore Fig.…”

Section: Resultsmentioning

confidence: 99%

“…4a. The SE images of re-melting cracks are compared to an SE image with a classical hot crack (solidification crack) from a sample with increased laser beam diameter of 116 μm from previous work, which leads to hot cracking, as explained in detail in [24]. The comparison should demonstrate the difference in cracking.…”

Section: Re-melting Cracksmentioning

confidence: 99%

“…To manufacture the LPBF- [22,23]. The process parameters from pre-studies, which create dense and crack-free CM247LC samples, as explained in detail in [24], are listed in Table 2, based on the classical definition of the energy density:…”

Section: Laser Powder Bed Fusionmentioning

confidence: 99%

“…Used process parameters, defined as reference for the LPBF process, referring to Gerstgrasser et al[24] …”

mentioning

confidence: 99%

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Residual stress reduction of LPBF-processed CM247LC samples via multi laser beam strategies

Gerstgrasser

Cloots²,

Stirnimann

et al. 2021

Int J Adv Manuf Technol

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Based on SLM parameters from previous works, which guarantee fully dense and crack free CM247LC samples, multi laser beam strategies have been pursued to reduce residual stresses or rather distortion during LPBF processing. By using a second post heating and non-melting laser source with a defocused laser beam and lateral offset, cantilever distortion is reduced more than 7.5%, compared to the reference. Based on pre-tests with 9 different offset parameters, the optimum offset has been identified. Also, an upper limit for the laser power of 65 W is identified for the second heat laser beam with a spot diameter of 380 μm, to avoid re-melting and creating new defects. A theoretical “two bar model,” to explain the residual stress behavior and reduction with multi laser beam offset strategy during the LPBF process, is presented. Furthermore, re-melting cracks, defects, and microstructure are analyzed in conjunction with the second defocused offset laser, in case of a 200 W laser power, an increased scan speed of 1300 mms/s, and a reduced hatch distance. Secondary electron signal (SE) images of re-melting cracks are analyzed and compared to SE-image of hot cracks (solidification cracks). Based on electron backscatter diffraction (EBSD), the results of the microstructure from the last mentioned multi laser beam approach, which creates re-melting cracks, are presented and analyzed.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Re-melting Cracksmentioning

confidence: 99%

Section: Laser Powder Bed Fusionmentioning

confidence: 99%

“…Used process parameters, defined as reference for the LPBF process, referring to Gerstgrasser et al[24] …”

mentioning

confidence: 99%

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Residual stress reduction of LPBF-processed CM247LC samples via multi laser beam strategies

Gerstgrasser

Cloots²,

Stirnimann

et al. 2021

Int J Adv Manuf Technol

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Thermokinetics, Microstructural Evolution, and Material Response

2022

Laser‐Based Additive Manufacturing

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Research progress on selective laser melting (SLM) of bulk metallic glasses (BMGs): a review

Zhang

Tan

Tian

et al. 2021

Int J Adv Manuf Technol

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Bulk metallic glasses (BMGs) are a subject of interest due to their superior specific properties such as low coefficient of friction, high strength, large ductility in bending, high elastic modulus, high microhardness, and high resistance to corrosion, oxidation, wear, and so on. However, BMGs are difficult to apply in industry due to their difficulty in manufacturing and secondary operation. In the past few decades, many efforts have been carried out to overcome the defects in the manufacturing of BMGs. It is difficult to fabricate complex structures with the whole amorphous alloy owing to the limit of crystallization and critical cooling rate. Additive manufacturing (AM), such as selective laser melting (SLM), can obtain relatively high cooling rates during the “layer-by-layer” process, which makes it possible to surpass the dimensional limitation of metallic glass. In the SLM process, the high-speed cooling of molten pool and the avoidance of secondary processing are very beneficial to the production and application of amorphous alloys. In this paper, based on the research of SLM additive manufacturing BMGs in recent years, the factors affecting crystallization and forming ability are discussed from many aspects according to different material systems. The status and challenges of SLM manufacturing BMGs including Fe-based, Zr-based, Al-based, and some composite-based BMGs will be presented. Mechanical properties and physicochemical properties were introduced. This review aims to introduce the latest developments in SLM additive manufacturing BMGs, especially on the development of process parameters, structure formation, simulation calculation, fracture mechanism, and crystallization behavior. With the traditional fabricating methods, BMGs were mainly used as a structure material. It will provide another alternative to use BMGs as a functional material by introducing SLM technology in amorphous preparation with complex geometry. This review summarizes the technical difficulty and application prospects of BMGs preparation by SLM and discusses the challenges and unresolved problems. This review identifies key issues that need to be addressed in this important field in the future. These problems are related to the application of BMGs as high-strength structural materials and new functional materials in the future.

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Focus shift analysis, to manufacture dense and crack-free SLM-processed CM247LC samples

Cited by 33 publications

References 18 publications

Residual stress reduction of LPBF-processed CM247LC samples via multi laser beam strategies

Residual stress reduction of LPBF-processed CM247LC samples via multi laser beam strategies

Thermokinetics, Microstructural Evolution, and Material Response

Research progress on selective laser melting (SLM) of bulk metallic glasses (BMGs): a review

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