Selective laser melting of typical metallic materials: An effective process prediction model developed by energy absorption and consumption analysis

Zhou, Yang; Zhang, Z.H.; Wang, Y.P.; Liu, G.; Zhou, Suyuan; Li, Y.L.; Shen, Jun; Yan, Ming

doi:10.1016/j.addma.2018.10.046

Cited by 71 publications

(28 citation statements)

References 40 publications

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“…Therefore, the absorption probability of the laser light is increased, consequently improving the optical absorption. 13,14 Although the laser irradiates on the melt pool (liquid) and not on the powder bed during the SLM process, 15 the effective optical absorption could have improved due to the continuous incorporation of the oxidized copper powder particles from the denudation zone into the melt pool, offering a fresh and optically absorptive powder surface. 15,16 Figure 2A shows the evolution of the relative density of the parts as a function of the applied volumetric energy density for different input power levels in an argon and nitrogen atmosphere.…”

Section: Methodsmentioning

confidence: 99%

“…Bergström reported on the enhanced laser absorption of bulk copper metal sheets at a wavelength of 1053 nm by the presence of surface oxides and surface roughness. Moreover, Zhou et al claimed that a layered structure on the powder surface significantly improves the powder optical absorption. Accordingly, the current investigation proposes an alternative approach to produce fully dense copper parts by using a surface‐oxidized copper powder for SLM.…”

Section: Introductionmentioning

confidence: 99%

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Mechanical and electrical properties of selective laser‐melted parts produced from surface‐oxidized copper powder

Jadhav

Zhang

Kruth

et al. 2019

Mat Design & Process Comms

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Selective laser melting of pure copper is challenging because of its high optical reflectivity and thermal conductivity. Accordingly, the surface of pure copper powder was modified by oxidation to enhance the optical absorption. The powder with improved optical absorption facilitated the production of crack‐free and dense copper parts at relatively lower laser energy density in both argon and nitrogen atmosphere. The microstructural analysis demonstrated the presence of stable melt tracks without obvious porosity. A very high electrical conductivity of approximately 89% of the international annealed copper standard, the hardness of approximately 93 HV, a tensile strength of approximately 270 MPa, and ductility of approximately 28% were achieved in the as‐built condition.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Mechanical and electrical properties of selective laser‐melted parts produced from surface‐oxidized copper powder

Jadhav

Zhang

Kruth

et al. 2019

Mat Design & Process Comms

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show abstract

“…This requires the use of materials parameters from the literature for this equiatomic high entropy alloy composition, with heat of fusion 56 60 , a comparison of this prediction is difficult. Measurements of grain boundary energy are sensitive to thermally-driven grain boundary segregation (and possibly phase separation) of impurities 61 .…”

Section: Ssmentioning

confidence: 99%

Evidence of Inverse Hall-Petch Behavior and Low Friction and Wear in High Entropy Alloys

Jones

Nation

Wellington-Johnson

et al. 2020

Sci Rep

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We present evidence of inverse Hall-petch behavior for a single-phase high entropy alloy (cocrfeMnni) in ultra-high vacuum and show that it is associated with low friction coefficients (~0.3). Grain size measurements by STEM validate a recently proposed dynamic amorphization model that accurately predicts grain size-dependent shear strength in the inverse Hall-Petch regime. Wear rates in the initially soft (coarse grained) material were shown to be remarkably low (~10-6 mm 3 /n-m), the lowest for any HEA tested in an inert environment where oxidation and the formation of mixed metal-oxide films is mitigated. the combined high wear resistance and low friction are linked to the formation of an ultra-nanocrystalline near-surface layer. The dynamic amorphization model was also used to predict an average high angle grain boundary energy (0.87 J/m 2). this value was used to explain cavitationinduced nanoporosity found in the highly deformed surface layer, a phenomenon that has been linked to superplasticity. Since their discovery in 2004 1,2 , high entropy alloys (HEAs) have been extensively investigated and shown to exhibit remarkable thermomechanical properties 3,4. Studies of grain-size dependent mechanical behavior are limited 5,6 , however, especially in the regime of ultra-nanocrystalline grain size where softening (i.e. inverse Hall-Petch behavior) occurs. Recent work has also shown that these alloys are ideally suited for processing using laser-based additive manufacturing techniques 7-9 , as they exhibit high phase stability and derive much of their strength from thermal history-insensitive mechanisms like solution strengthening 10. While recent publications have presented experimental evidence of low friction or high wear resistance (but typically not both) with HEAs 11-25 , they were performed in environments where oxidation and the formation of mixed metal-oxide surface films was prevalent. These phenomena can greatly impact strength and deformation/wear resistance. We show that in an ultra-high vacuum (UHV) environment, i.e., in the absence of chemically reactive species, an additively manufactured initially coarse grained (soft), single-phase HEA exhibited a tendency toward low friction coefficients (i.e., low shear strength) and some of the lowest wear rates currently reported for these materials. The low friction and wear are attributed to a propensity for extreme grain refinement under sliding contact. Specifically, we present evidence of that this high strain rate shear leads to dynamic amorphization and inverse Hall-Petch behavior in the surface layer. In the present context of sliding contacts, dynamic amorphization refers to the continuous shear-induced generation of a structurally amorphous layer that accommodates deformation 26. This is in competition with stress-and temperature-driven grain growth and recrystallization, all of which reestablish crystallinity and order in the shear layer. The shear layer must be amorphized again in subsequent contact passes, thus we refer to this process as dynam...

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“…Several research groups are working to develop physical models to describe, and consequently control, the process, with some examples being described in [58][59][60][61][62][63][64][65][66][67][68][69]. Developed models also aim at defect forecasting and mitigation [70][71][72][73][74][75]. It is of major relevance to remember that, unlike conventional processes, all AM technologies are producing the alloy and the specific geometry to be put in service simultaneously.…”

Section: Laser Powder Bed Fusion Working Principles and Process-relatmentioning

confidence: 99%

Laser Powder Bed Fusion of Stainless Steel Grades: A Review

Zitelli¹,

Folgarait²,

Schino

2019

Metals

101

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In this paper, the capability of laser powder bed fusion (L-PBF) systems to process stainless steel alloys is reviewed. Several classes of stainless steels are analyzed (i.e., austenitic, martensitic, precipitation hardening and duplex), showing the possibility of satisfactorily processing this class of materials and suggesting an enlargement of the list of alloys that can be manufactured, targeting different applications. In particular, it is reported that stainless steel alloys can be satisfactorily processed, and their mechanical performances allow them to be put into service. Porosities inside manufactured components are extremely low, and are comparable to conventionally processed materials. Mechanical performances are even higher than standard requirements. Micro surface roughness typical of the as-built material can act as a crack initiator, reducing the strength in both quasi-static and dynamic conditions.

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Selective laser melting of typical metallic materials: An effective process prediction model developed by energy absorption and consumption analysis

Cited by 71 publications

References 40 publications

Mechanical and electrical properties of selective laser‐melted parts produced from surface‐oxidized copper powder

Mechanical and electrical properties of selective laser‐melted parts produced from surface‐oxidized copper powder

Evidence of Inverse Hall-Petch Behavior and Low Friction and Wear in High Entropy Alloys

Laser Powder Bed Fusion of Stainless Steel Grades: A Review

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