Tensile properties of selective laser melting products affected by building orientation and energy density

Pal, Snehashis; Gubeljak, Nenad; Hudák, Radovan; Lojen, Gorazd; Rajťúková, Viktória; Predan, Jožef; Kokol, Vanja; Drstvenšek, Igor

doi:10.1016/j.msea.2018.11.130

Cited by 70 publications

(28 citation statements)

References 31 publications

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“…To limit these issues, adapted process parameters are needed for a stable fabrication of lattice structures made of Ti6Al7Nb. After examining the literature recommendations regarding the SLM process parameters which could be proper for Ti6Al7Nb powder [ 20 , 35 ], and based on our previous studies [ 42 , 44 , 45 , 46 ], we programmed and tested more than 10 laser parameters. To have an efficient production speed, the layer thickness was maintained constant at 50 µm.…”

Section: Methodsmentioning

confidence: 99%

Physical–Mechanical Characteristics and Microstructure of Ti6Al7Nb Lattice Structures Manufactured by Selective Laser Melting

et al. 2020

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The demand of lattice structures for medical applications is increasing due to their ability to accelerate the osseointegration process, to reduce the implant weight and the stiffness. Selective laser melting (SLM) process offers the possibility to manufacture directly complex lattice applications, but there are a few studies that have focused on biocompatible Ti6Al7Nb alloy. The purpose of this work was to investigate the physical–mechanical properties and the microstructure of three dissimilar lattice structures that were SLM-manufactured by using Ti6Al7Nb powder. In particular, the strut morphology, the fracture characterization, the metallographic structure, and the X-ray phase identification were analyzed. Additionally, the Gibson-Ashby prediction model was adapted for each lattice topology, indicating the theoretical compressive strength and Young modulus. The resulted porosity of these lattice structures was approximately 56%, and the pore size ranged from 0.40 to 0.91 mm. Under quasi-static compression test, three failure modes were recorded. Compared to fully solid specimens, the actual lattice structures reduce the elastic modulus from 104 to 6–28 GPa. The struts surfaces were covered by a large amount of partial melted grains. Some solidification defects were recorded in struts structure. The fractographs revealed a brittle rupture of struts, and their microstructure was mainly α’ martensite with columnar grains. The results demonstrate the suitability of manufacturing lattice structures made of Ti6Al7Nb powder having unique physical–mechanical properties which could meet the medical requirements.

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Section: Methodsmentioning

confidence: 99%

Physical–Mechanical Characteristics and Microstructure of Ti6Al7Nb Lattice Structures Manufactured by Selective Laser Melting

et al. 2020

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“…Anyway, rapid cooling, i.e., quenching, results in martensitic transformation of the undercooled NiTi. At the equiatomic chemical composition, the martensite start temperature should be at approximately 47-48 • C [22]. As the difference between the martensite-start and finish temperature of nitinol alloys does not exceed 20-25 • C [36,37], at room temperature the quenched alloy should be martensitic and capable of shape memory effect.…”

Section: The Nitinol Preparationmentioning

confidence: 99%

“…Even the high standards of the aerospace industry can be met [20]. Nevertheless, it is still a challenge to produce a flawless product with the intended characteristics [21], and the building orientation has an impact on the mechanical properties [22]. Besides, in spite of the high quality of AM parts, post-processing involving hot working, cold working [17], conventional machining [23], heat treatments and surface treatments, enhances the shape memory properties [24], corrosion resistance and biocompatibility.…”

Section: Introductionmentioning

confidence: 99%

Experimental Continuous Casting of Nitinol

Lojen

Stambolić

Batič

et al. 2020

Metals

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Commercially available nitinol is currently manufactured using classic casting methods that produce blocks, the processing of which is difficult and time consuming. By continuous casting, wherein molten metal solidifies directly into a semi-finished product, the casting and processing of ingots can be avoided, which saves time and expense. However, no reports on continuous casting of nitinol could be found in the literature. In this work, Φ 12 mm nitinol strands were continuously cast. Using a graphite crucible, smelting of pure Ni and Ti in a medium frequency induction furnace is difficult, because it is hard to prevent a stormy reaction between Ni and Ti and to reach a homogeneous melt without a prolonged long holding time. Using a clay-graphite crucible, the stormy reaction is easily controlled, while effective stirring assures a homogeneous melt within minutes. Strands of nearly equiatomic chemical compositions were obtained with acceptable surface quality. The microstructure of strands containing over 50 at. % Ni, consisted of Ti2Ni and cubic NiTi, whereas the microstructure of strands containing less than 50 at. % Ni consisted of TiNi3 and cubic NiTi. This is consonant with the results of some other authors, and indicates that the eutectoid decomposition NiTi → Ti2Ni + TiNi3 does not take place.

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“…Additionally, at the highest ED, a huge spattering of material was observed that caused a reduction of material, which led to the lowering of the height. 19,20 During scanning of the starting layer on the support structure, the first layer melt-pool volume depends on ED, and the higher ED caused a higher melt-pool volume, 19 which occupied the area below the expected bottom surface of the product. Therefore, rising the ED from 39 J/mm 3 to 195 J/mm 3 caused higher additional dimensions from the set-I-1 to set-I-2, respectively.…”

Section: Cuboid Samples Dimensionsmentioning

confidence: 99%

Dimensional errors in selective laser melting products related to different orientations and processing parameters

Pal¹,

Kokol²,

Gubeljak³

et al. 2019

Mater. Tehnol.

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This research has investigated the changes of dimensions with changes of the Energy Density (ED), processing parameters and build up direction wise of Ti-6Al-4V alloy products manufactured by the Selective Laser Melting (SLM) process. The selected processing parameters were laser power, scanning speed, and hatch spacing in several combinations, keeping the layer thickness constant during all three steps of the studies. Four orientations have been considered for a specimen to build up in different directions for each of the selected combinations of processing parameters. The SLM process is characterized by the high laser energy inputs into a metallic powder layer in a short interaction time that occurs several thermal related issues that significantly affect the shape and dimensions of the part. The results show that ED, as well as its processing parameters, have significant influences on the product's dimensions. The building orientation has a great impact on the dimensional accuracy.

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Tensile properties of selective laser melting products affected by building orientation and energy density

Cited by 70 publications

References 31 publications

Physical–Mechanical Characteristics and Microstructure of Ti6Al7Nb Lattice Structures Manufactured by Selective Laser Melting

Physical–Mechanical Characteristics and Microstructure of Ti6Al7Nb Lattice Structures Manufactured by Selective Laser Melting

Experimental Continuous Casting of Nitinol

Dimensional errors in selective laser melting products related to different orientations and processing parameters

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