scholarly journals Interplay of viscosity and surface tension for ripple formation by laser melting

2022 ◽  
Vol 105 (3) ◽  
Author(s):  
K. Morawetz ◽  
S. Trinschek ◽  
E. L. Gurevich
Keyword(s):  
Surface Tension ◽  
Laser Melting ◽  
Ripple Formation

Fundamental Study on Laser Interactions With Nanoparticles-Reinforced Metals—Part II: Effect of Nanoparticles on Surface Tension, Viscosity, and Laser Melting

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
Chao Ma ◽  
Jingzhou Zhao ◽  
Chezheng Cao ◽  
Ting-Chiang Lin ◽  
Xiaochun Li
Keyword(s):  
Surface Tension ◽  
Surface Roughness ◽  
Thermophysical Properties ◽  
Melting Process ◽  
Laser Melting ◽  
Fundamental Study ◽  
Laser Polishing ◽  
Laser Manufacturing ◽  
Manufacturing Technologies ◽  
Laser Interactions

It is of great scientific and technical interests to conduct fundamental studies on the laser interactions with nanoparticles-reinforced metals. This part of the study presents the effects of nanoparticles on surface tension and viscosity, thus the heat transfer and fluid flow, and eventually the laser melting process. In order to determine the surface tension and viscosity of nanoparticles-reinforced metals, an innovative measurement system was developed based on the characteristics of oscillating metal melt drops after laser melting. The surface tensions of Ni/Al2O3 (4.4 vol. %) and Ni/SiC (3.6 vol. %) at ∼1500 °C were 1.39 ± 0.03 N/m and 1.57 ± 0.06 N/m, respectively, slightly lower than that of pure Ni, 1.68 ± 0.04 N/m. The viscosities of these Ni/Al2O3 and Ni/SiC MMNCs at ∼1500 °C were 13.3 ± 0.8 mPa·s and 17.3 ± 3.1 mPa·s, respectively, significantly higher than that of pure Ni, 4.8 ± 0.3 mPa·s. To understand the influences of the nanoparticles-modified thermophysical properties on laser melting, an analytical model was used to theoretically predict the melt pool flows using the newly measured material properties from both Part I and Part II. The theoretical analysis indicated that the thermocapillary flows were tremendously suppressed due to the significantly increased viscosity after the addition of nanoparticles. To test the hypothesis that laser polishing could significantly benefit from this new phenomenon, systematic laser polishing experiments at various laser pulse energies were conducted on Ni/Al2O3 (4.4 vol. %) and pure Ni for comparison. The surface roughness of the Ni/Al2O3 was reduced from 323 nm to 72 nm with optimized laser polishing parameters while that of pure Ni only from 254 nm to 107 nm. The normalized surface roughness reduced by nearly a factor of two with the help of nanoparticles, validating the feasibility to tune thermophysical properties and thus control laser-processing outcomes by nanoparticles. It is expected that the nanoparticle approach can be applied to many laser manufacturing technologies to improve the process capability and broaden the application space.

scholarly journals Morphological Development of Sub-Grain Cellular/Bands Microstructures in Selective Laser Melting

Materials ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1204 ◽  
Author(s):  
Xihe Liu ◽  
Xin Zhou ◽  
Ben Xu ◽  
Jing Ma ◽  
Congcong Zhao ◽  
...  
Keyword(s):  
Surface Tension ◽  
Selective Laser Melting ◽  
Single Layer ◽  
Liquid Interface ◽  
Morphological Development ◽  
Eutectic Alloys ◽  
Laser Melting ◽  
Submicron Scale ◽  
Solid Liquid Interface ◽  
Solid Liquid

In this paper, single-layer and bulk 316 L selective laser melting (SLM) experiments were conducted, fine submicron-scale geometric symmetrical cellular (hexagonal, pentagonal and square), elongated cellular and bands solidification morphologies were found in the laser-melt top surface. Meanwhile, morphological developed sub-grain patterns with quasi-hexagonal cellular, elongated cellular and bands structures (size ~1 μm) coexisting inside one single macro-solidified grain were also identified. This demonstrated the transitions from quasi-hexagonal-cells to elongated cells/bands, and transitions reverse, occurred in the whole bulk under some circumstances during SLM. Based on the experimental realities, these morphologies are formed by the local convection and Bénard instabilities in front of the solid/liquid interface (so-called mushy zones) affected by intricate temperature and surface tension gradients. Quasi-hexagonal cellular convective fields are then superimposed on macro-grain solidification to form the sub-grain patterns and micro-segregations. This explanation seems reasonable and is unifying as it can be expanded to other eutectic alloys with face center cubic (FCC) prevenient phase prepared by SLM, e.g., the Al-Si and Co-Cr-Mo systems.

Investigation on mechanism of surface tension on morphology of melt track in selective laser melting processing

2018 ◽  
Vol 124 (10) ◽  
Author(s):  
Xiangdong Chen ◽  
Hucheng Tian ◽  
Zhaohua Yan ◽  
Xinlei Zhi ◽  
Jun Zhang ◽  
...  
Keyword(s):  
Surface Tension ◽  
Selective Laser Melting ◽  
Laser Melting

Influence of surface tension on the molten pool morphology in laser melting

2019 ◽  
Vol 146 ◽  
pp. 106075 ◽  
Author(s):  
Shibai Liu ◽  
Jichang Liu ◽  
Jinxuan Chen ◽  
Xudong Liu
Keyword(s):  
Surface Tension ◽  
Molten Pool ◽  
Laser Melting

Highly nonlinear standing water waves with small capillary effect

1998 ◽  
Vol 369 ◽  
pp. 253-272 ◽  
Author(s):  
WILLIAM W. SCHULTZ ◽  
JEAN-MARC VANDEN-BROECK ◽  
LEI JIANG ◽  
MARC PERLIN
Keyword(s):  
Surface Tension ◽  
Water Waves ◽  
Standing Waves ◽  
High Amplitude ◽  
Boundary Integral ◽  
Boundary Integral Method ◽  
Ripple Formation ◽  
Node Distribution ◽  
Highly Nonlinear ◽  
Periodic Standing Waves

We calculate spatially and temporally periodic standing waves using a spectral boundary integral method combined with Newton iteration. When surface tension is neglected, the non-monotonic behaviour of global wave properties agrees with previous computations by Mercer & Roberts (1992). New accurate results near the limiting form of gravity waves are obtained by using a non-uniform node distribution. It is shown that the crest angle is smaller than 90° at the largest calculated crest curvature. When a small amount of surface tension is included, the crest form is changed significantly. It is necessary to include surface tension to numerically reproduce the steep standing waves in Taylor's (1953) experiments. Faraday-wave experiments in a large-aspect-ratio rectangular container agree with our computations. This is the first time such high-amplitude, periodic waves appear to have been observed in laboratory conditions. Ripple formation and temporal symmetry breaking in the experiments are discussed.

Forming Mechanism of Bump Shape in Pulsed Laser Melting of Stainless Steel

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Hong Shen ◽  
Yanqing Pan ◽  
Jing Zhou ◽  
Zhenqiang Yao
Keyword(s):  
Surface Tension ◽  
Stainless Steel ◽  
Free Surface ◽  
Surface Deformation ◽  
Pulsed Laser ◽  
Element Model ◽  
Surface Tension Gradient ◽  
Laser Melting ◽  
Cooling Period ◽  
Free Surface Deformation

Laser surface topography has great applications in mechanical, medical, and electrical industries. This paper proposes a mechanism for the shape formation of stainless steel by pulsed laser melting. A 2D axisymmetric finite element model considering the temperature-dependent surface tension is developed, in which the melt flow and free surface deformation are analyzed by using the normal and shear surface forces. The numerical results show that the molten flows toward the place of the greatest surface tension and the free surface deformation are dominated by the shear force (Marangoni effects), generated by the surface tension gradient during heating phase, and the normal stress, generated by the surface tension at the curved surface during the cooling period.

Immunoferritin localization of intracellular antigens in positively stained frozen sections

1978 ◽  
Vol 36 (2) ◽  
pp. 168-169
Author(s):  
K. T. Tokuyasu
Keyword(s):  
Surface Tension ◽  
Water Surface ◽  
Thin Layers ◽  
The Other ◽  
Positive Staining ◽  
Frozen Sections ◽  
The Past ◽  
Ultrathin Frozen Sections ◽  
Definition Of

During the past investigations of immunoferritin localization of intracellular antigens in ultrathin frozen sections, we found that the degree of negative staining required to delineate u1trastructural details was often too dense for the recognition of ferritin particles. The quality of positive staining of ultrathin frozen sections, on the other hand, has generally been far inferior to that attainable in conventional plastic embedded sections, particularly in the definition of membranes. As we discussed before, a main cause of this difficulty seemed to be the vulnerability of frozen sections to the damaging effects of air-water surface tension at the time of drying of the sections.Indeed, we found that the quality of positive staining is greatly improved when positively stained frozen sections are protected against the effects of surface tension by embedding them in thin layers of mechanically stable materials at the time of drying (unpublished).

The Critical Point Drying Method Applied to Scanning Electron Microscopy of L-929 Cells

1970 ◽  
Vol 28 ◽  
pp. 278-279
Author(s):  
Charles TurnbiLL ◽  
Delbert E. Philpott
Keyword(s):  
Electron Microscopy ◽  
Carbon Dioxide ◽  
Surface Tension ◽  
Critical Point ◽  
Freeze Drying ◽  
Attractive Alternative ◽  
Crystal Formation ◽  
Critical Point Drying ◽  
Time Required ◽  
Scanning Electron

The advent of the scanning electron microscope (SCEM) has renewed interest in preparing specimens by avoiding the forces of surface tension. The present method of freeze drying by Boyde and Barger (1969) and Small and Marszalek (1969) does prevent surface tension but ice crystal formation and time required for pumping out the specimen to dryness has discouraged us. We believe an attractive alternative to freeze drying is the critical point method originated by Anderson (1951; for electron microscopy. He avoided surface tension effects during drying by first exchanging the specimen water with alcohol, amy L acetate and then with carbon dioxide. He then selected a specific temperature (36.5°C) and pressure (72 Atm.) at which carbon dioxide would pass from the liquid to the gaseous phase without the effect of surface tension This combination of temperature and, pressure is known as the "critical point" of the Liquid.

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