scholarly journals Tailoring of Microstructures and Tensile Properties in the Solidification of Al-11Si(-xCu) Brazing Alloys

Metals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 784 ◽  
Author(s):  
Bruno Donadoni ◽  
Leonardo Gomes ◽  
Amauri Garcia ◽  
José Spinelli
Keyword(s):  
Tensile Properties ◽  
Scaling Laws ◽  
Critical Role ◽  
Ternary Eutectic ◽  
Eutectic Mixture ◽  
Cu Alloys ◽  
Dendritic Length ◽  
Solidification Kinetics ◽  
Eutectic Front ◽  
Filler Metals

Ternary Al-11wt %Si-(xwt %)Cu alloys are highly recommended as commercial filler metals for aluminum brazing alloys. However, very little is known about the functional inter-relations controlling the solidified microstructures characterizing processes such as torch and furnace brazing. As such, we evaluated two commercial brazing alloys, which are the Al-11wt %Si-3.0wt %Cu and Al-11wt %Si-4.5wt %Cu alloys: Cu contents typically trend in between the suitable alloying spectrum. We analyzed the effects of solidification kinetics over features such as the dendrite arm spacing and the spacing between particles constituting the eutectic mixture. Also, tensile properties were determined as a function of the dendrite microstructure dimensions. The parameters concerned for translating the solidification kinetics were either the cooling rate, or growth velocity related to the displacement of the dendrite tip, or the eutectic front. The relevant scaling laws representing the growth of these brazing alloys are outlined. The experimental results demonstrated that a 50% increase in Cu alloying (from 3.0 to 4.5 wt %) could be operated in order to obtain significant variations in the dendritic length-scale of the microstructure across the produced parts. Overall, the microstructures were constituted by an α-Al dendritic matrix surrounded by a ternary eutectic consisting of α-Al + Al2Cu + Si. The scale measurements committed to the Al2Cu eutectic phase pointed out that the increase in Cu alloying has a critical role on refining the ternary eutectic.

Length scale of the dendritic microstructure affecting tensile properties of Al–(Ag)–(Cu) alloys

2016 ◽  
Vol 30 (03) ◽  
pp. 1550261 ◽  
Author(s):  
Roberto N. Duarte ◽  
Jonas D. Faria ◽  
Crystopher Brito ◽  
Nathalia C. Veríssimo ◽  
Noé Cheung ◽  
...  
Keyword(s):  
Tensile Properties ◽  
Ternary Eutectic ◽  
Eutectic Mixture ◽  
Dendritic Morphology ◽  
Homogeneous Distribution ◽  
Length Scale ◽  
Dendritic Microstructure ◽  
Cu Alloys ◽  
Wide Range ◽  
Dendritic Arm Spacing

The dependence of tensile properties on the length scale of the dendritic morphology of Al–Cu, Al–Ag and Al–Ag–Cu alloys is experimentally investigated. These alloys were directionally solidified (DS) under a wide range of cooling rates [Formula: see text], permitting extensive microstructural scales to be examined. Experimental growth laws are proposed relating the primary dendritic arm spacing, [Formula: see text] to [Formula: see text] and tensile properties to [Formula: see text]. It is shown that the most significant effect of the scale of [Formula: see text] on the tensile properties is that of the ternary alloy, which is attributed to the more homogeneous distribution of the eutectic mixture for smaller [Formula: see text] and by the combined reinforcement roles of the intermetallics present in the ternary eutectic: Al2Cu and nonequilibrium Ag3Al.

Micro Thermal Engines: Is There Any Room at the Bottom?

1999 ◽  
Author(s):  
Richard B. Peterson
Keyword(s):  
Heat Transfer ◽  
Scaling Laws ◽  
Critical Role ◽  
Heat Engine ◽  
Engine Performance ◽  
Characteristic Size ◽  
Operating Efficiency ◽  
Simple Scaling ◽  
Small Structure ◽  
Micro Heat Engine

Abstract Richard P. Feynman introduced the field of microscale and nanoscale engineering in 1959 by giving a talk on how to make things very small. Feynman’s premise was that no fundamental physical laws limit the size of a machine down to the microscopic level. Is this true for all types of machines? Are micro thermal devices fundamentally different than mechanically-based machines with respect to their scaling laws? This paper demonstrates that micro thermal engines do indeed suffer serious performance degradation as their characteristic size is reduced. A micro thermal engine, and more generally, any thermally-based micro device, depends on establishing a temperature difference between two regions within a small structure. In this paper, the performance of a micro thermal engine is explored as a function of the characteristic length parameter, L. In the development, the important features of thermal engines are discussed in the context of developing simple scaling laws predicting the dependency of the operating efficiency on L. After this is accomplished, a general model is derived for a heat engine operating between two temperature reservoirs and having both intrinsic and extrinsic sources of irreversibility, i.e. thermal conductances and heat leakage paths for the heat flow. With this model and typical numerical values for the conductances, micro heat engine performance is predicted as the characteristic size is reduced. This paper demonstrates that under at least one particular formulation of the problem, there may indeed be some room at the bottom. However, heat transfer does play a critical role in determining micro engine performance and depending on how the heat transfer through the engine is modeled, vanishingly small efficiencies can result as the characteristic engine size goes to zero.

scholarly journals Relationship between fracture toughness and tensile properties in Al-Zn-Mg-Cu alloys.

1985 ◽  
Vol 35 (6) ◽  
pp. 353-358 ◽  
Author(s):  
Kenji HIGASHI ◽  
Yasushi HIRAI ◽  
Tadakazu OHNISHI
Keyword(s):  
Fracture Toughness ◽  
Tensile Properties ◽  
Cu Alloys

Effect of equal channel angular pressing on tensile properties and fracture modes of casting Al–Cu alloys

2006 ◽  
Vol 426 (1-2) ◽  
pp. 305-313 ◽  
Author(s):  
D.R. Fang ◽  
Z.F. Zhang ◽  
S.D. Wu ◽  
C.X. Huang ◽  
H. Zhang ◽  
...  
Keyword(s):  
Tensile Properties ◽  
Equal Channel Angular Pressing ◽  
Fracture Modes ◽  
Angular Pressing ◽  
Cu Alloys

scholarly journals Measuring T Tauri star magnetic fields

2008 ◽  
Vol 4 (S259) ◽  
pp. 345-356 ◽  
Author(s):  
Christopher M. Johns–Krull
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Scaling Laws ◽  
Main Sequence ◽  
Critical Role ◽  
X Rays ◽  
Stellar Rotation ◽  
T Tauri ◽  
Dipole Component ◽  
Stellar Magnetic Fields

AbstractStellar magnetic fields including a strong dipole component are believed to play a critical role in the early evolution of newly formed stars and their circumstellar accretion disks. It is currently believed that the stellar magnetic field truncates the accretion disk several stellar radii above the star. This action forces accreting material to flow along the field lines and accrete onto the star preferentially at high stellar latitudes. It is also thought that the stellar rotation rate becomes locked to the Keplerian velocity near the radius where the disk is truncated. This paper reviews recent efforts to measure the magnetic field properties of low mass pre-main sequence stars, focussing on how the observations compare with the theoretical expectations. A picture is emerging indicating that quite strong fields do indeed cover the majority of the surface on these stars; however, the dipole component of the field appears to be alarmingly small. The current measurements also suggest that given their strong magnetic fields, T Tauri stars are somewhat faint in X-rays relative to what is expected from simple main sequence star scaling laws.

scholarly journals Relationship Between Microstructure Evolution and Tensile Properties of AlSi10mg Alloys With Varying Solidification Cooling Rates

2021 ◽  
Author(s):  
Maressa Gandolfi ◽  
Marcella Gautê Xavier ◽  
Leonardo Fernandes Gomes ◽  
Rodrigo Valenzuela Reyes ◽  
Amauri Garcia ◽  
...  
Keyword(s):  
Tensile Properties ◽  
Cooling Rate ◽  
Experimental Evolution ◽  
Ternary Eutectic ◽  
High Growth ◽  
Directionally Solidified ◽  
Dendritic Spacing ◽  
Cooling Rates ◽  
Dendritic Array ◽  
Mg Content

This work explored and contrasted the effect of microstructure on the tensile properties of AlSi10Mg alloys generated by transient directional solidification depending on variations in cooling rate and Magnesium (Mg) content (i.e., 0.45 and 1wt.% Mg), with a focus on understanding the dendritic growth and phases constitution. Optical and Scanning electron (SEM) microscopies, CALPHAD and thermal analysis were used to describe the microstructure, forming phases and resulting tensile properties. The findings showed that the experimental evolution of the primary dendritic spacing is very similar when both directionally solidified (DS) Al-10wt.% Si-0.45wt.% Mg and Al-10wt.% Si-1wt.% Mg alloys samples are compared. The secondary dendritic spacing was lower for the alloy with more Mg, especially considering the range of high growth velocities. Moreover, a greater fraction of (Al+Si+Mg2Si) ternary eutectic islands surrounding the -Al dendritic matrix was noted for the alloy with 1wt.% Mg. As a result of primary dendritic spacings greater than 180 m related to lower cooling rates, slightly higher tensile properties were attained for the Al-10wt.% Si-0.45wt.% Mg alloy. In contrast, combining dendritic refining (< 150 m) and larger Mg2Si fraction, fast solidified DS Al-10wt.% Si-1wt.% Mg samples exhibited higher tensile strength and elongation. The control of cooling rate and fineness of the dendritic array provided a new insight related to the addition of Mg in slightly higher levels than conventional ones, capable of achieving a better balance of tensile properties in AlSi10Mg alloys.

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