Microstructural characterization of aluminum alloys using Weck's reagent, part II: Coloring mechanism

Gao, Li; Harada, Yoshio; Kumai, Shinji

doi:10.1016/j.matchar.2015.05.006

Cited by 17 publications

(21 citation statements)

References 13 publications

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“…The addition of different solutes can also affect the surface chemical reactions and, therefore, the colors change as a result. 24,25 Since Al and various alloying elements as well as the selected cladding powders have significant differences in their chemical and physical properties, the interface region and the laser-melted regions display an inhomogeneous composition that is consistent with previous scientific reports by Wang et al 10,11 Color etching is very well suited to characterizing laser-surface-modified aluminum specimens. It can be recommended as a valuable step in the metallographic analysis of laser-melted aluminum specimens.…”

Section: Metallographic Analysessupporting

confidence: 77%

“…23 The color differences in the surrounding regions of the melt pool can be ascribed to the micro-segregation-sensitive nature of Weck's reagent. 24,25 Outside the melt pool, the dendritic nature of the initial microstructure is seen. The shape of the melt pool is determined using three different isotherms: a) the liquidus temperature of the substrate material ahead of the laser beam, as the substrate has to be melted to ensure a metallurgical bond; b) the liquidus temperature of the coating material; and c) the solidus temperature of the coating material.…”

Section: Metallographic Analysesmentioning

confidence: 99%

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Sensitivity of Weck’s reagent to the microstructure inhomogeneities of a pulse-laser-modified AlSi12CuNiMg alloy

Petrovič¹,

Šturm²

2018

Mater. Tehnol.

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In order to optimize laser cladding using pulsed-laser procedures, in particular to prevent failures of the cladding, a systematic ex-situ characterization can provide a lot of valuable information about the effects of the process parameters on the resulting microstructure and hardness. In this study, a TiC/TiB2 cladded layer was produced by laser scanning over a pre-placed TiC/TiB2/Al powder mixture on an aluminum alloy using a Nd:YAG pulsed laser. The increasing of the EEDV (effective energy density per volume) influences larger scattering of the cladded-layer thickness, whereas the decreasing of the EEDV influences the decrease of its surface roughness. The average hardness of the 0.1-mm-thick layer was 400±10 HV 0.3, which confirmed an improvement in the mechanical properties of the surface. The microstructures were investigated using FE-SEM/EDS and light microscopy. An additional color chemical etching using Weck's reagent at room temperature was performed. Using color etching, the laser-affected features, i.e., the penetration depth, the melt pool, its boundaries and various inhomogeneities, could be clearly distinguished. The sensitivity of the color etchant to the morphological and compositional differences was confirmed by FE-SEM/EDS analyses and microhardness measurements.

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Section: Metallographic Analysessupporting

confidence: 77%

Section: Metallographic Analysesmentioning

confidence: 99%

Sensitivity of Weck’s reagent to the microstructure inhomogeneities of a pulse-laser-modified AlSi12CuNiMg alloy

Petrovič¹,

Šturm²

2018

Mater. Tehnol.

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“…The manual point count from ASTM E562-11 [13] was followed for the measurements of the solid fraction on micrographs obtained from polished surfaces etched with Weck's reagent (4 g KMnO 4 , 1 g NaOH and 100 mL distilled water), with a contact time of 12 seconds. Gao et al [14] analyzed the coloring mechanism of the Weck's reagent in A356 alloy specimens quenched in water from the semisolid range. A manganese oxide film formed on the aluminum sample, which was responsible for a brown color with varying brightnesses in the a-Al globules observed in the optical microscope.…”

Section: B Microstructural Characterizationmentioning

confidence: 99%

“…Electron probe microanalysis and roughness measurements in the a-Al globules showed that in regions where silicon segregated, a smooth interface is formed between the manganese oxide film and the a-Al globules. [14] The smooth interface results in a brighter area observed in the periphery of the a-Al globules compared with the darker color in the core of the a-Al globules (where the interface between the manganese oxide film and the substrate have greater roughness). In a further study, Gao et al [15] measured the solid fraction of a titanium-containing A356 aluminum alloy that was heated and isothermally held at a pre-determined temperature in the semi-solid range.…”

Section: B Microstructural Characterizationmentioning

confidence: 99%

Influence of Grain Refinement on Slurry Formation and Surface Segregation in Semi-solid Al-7Si-0.3Mg Castings

Santos

Kallien

Jarfors

et al. 2018

Metall Mater Trans A

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This study aims to evaluate the effect of grain refinement on slurry formation and surface segregation in semi-solid castings produced by the Rheometalä process. The effect of two grain refiners, Al-8B and Al-5Ti-1B, on the slurry a-Al grain size, shape factor and solid fraction was evaluated. The results suggest that the addition of a grain refiner can affect the solid fraction obtained in the Rheometal TM process and, consequently, reduce the solute content near the casting surface. Grain refiner addition resulted in a larger fraction of a-Al grains £ 60 lm for the refined alloys compared with the unrefined alloy. Additionally, the growth of a-Al slurry globules was greater for the unrefined alloy compared with the refined alloy during solidification in the die-cavity. A more homogeneous and finer microstructure was observed near the surface in the grain-refined castings compared with the unrefined castings. Evidence of significant liquid penetration was identified in some a-Al globules, indicating that disintegration of a-Al globules may occur during the Rheometalä casting process.

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“…Using Weck's reagent to avoid the overestimation can be regard as a modified quantitative metallography. 9,12,13) The microstructure analysis was performed only for the small size specimens, which were cooled at a fixed cooling rate. In order to perform the die-casting for preparing the tensile specimen for future works, much larger size billets were used.…”

Section: Introductionmentioning

confidence: 99%

Microstructure Analysis of Quenched Semi-Solid A356 Aluminum Alloy Slurry by Using Weck’s Reagent

et al. 2020

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The semi-solid slurry of A356 alloy of various solid fractions was fabricated and water quenched to freeze the morphology of the Al grains in the semi-solid state. Two kinds of specimens with different volume (large and small) were prepared to change the cooling rate during the quenching. The difference in the amount of solid growth around the original spherical Al grains during the quenching was investigated by the color etching method with Weck's reagent, which is sensitive to the solute segregation. It was found that the amount of solid growth during the quenching increased with a decreasing cooling rate. The amount of solid growth of each spherical Al grain also increased for a decreasing local solid fraction, or the amount of residual liquid and the mutual distance between the solid grains. The solid fraction obtained by the color etching method showed a good agreement with the estimated solid fraction from the phase diagram. It was confirmed that the present color metallography was effective to evaluate the correct solid fraction at the semi-solid state.

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Microstructural characterization of aluminum alloys using Weck's reagent, part II: Coloring mechanism

Cited by 17 publications

References 13 publications

Sensitivity of Weck’s reagent to the microstructure inhomogeneities of a pulse-laser-modified AlSi12CuNiMg alloy

Sensitivity of Weck’s reagent to the microstructure inhomogeneities of a pulse-laser-modified AlSi12CuNiMg alloy

Influence of Grain Refinement on Slurry Formation and Surface Segregation in Semi-solid Al-7Si-0.3Mg Castings

Microstructure Analysis of Quenched Semi-Solid A356 Aluminum Alloy Slurry by Using Weck’s Reagent

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