A model of grain refinement incorporating alloy constitution and potency of heterogeneous nucleant particles

Easton, Mark; StJohn, David H.

doi:10.1016/s1359-6454(00)00368-2

Cited by 514 publications

(264 citation statements)

References 20 publications

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“…[11][12][13][14][15] In addition, the growth restriction factor is equivalent to the rate of development of constitutional undercooling (DT c ) relative to the rate of development of solid (f s ). [16] Recent work includes the work of Tamirisakandala et al who reported the effect of boron on the grain refinement of as-cast Ti-6Al-4V and Ti-6242 [17] and Bermingham et al who studied the same effect for as-cast commercially pure titanium.…”

Section: The High Level Of Interest In Additive Manufacturingmentioning

confidence: 99%

Microstructures and Grain Refinement of Additive-Manufactured Ti-xW Alloys

Mendoza

Samimi

Brice

et al. 2017

Metall Mater Trans A

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It is necessary to better understand the composition-processing-microstructure relationships that exist for materials produced by additive manufacturing. To this end, Laser Engineered Net Shaping (LENSä), a type of additive manufacturing, was used to produce a compositionally graded titanium binary model alloy system (Ti-xW specimen (0 £ x £ 30 wt pct), so that relationships could be made between composition, processing, and the prior beta grain size. Importantly, the thermophysical properties of the Ti-xW, specifically its supercooling parameter (P) and growth restriction factor (Q), are such that grain refinement is expected and was observed. The systematic, combinatorial study of this binary system provides an opportunity to assess the mechanisms by which grain refinement occurs in Ti-based alloys in general, and for additive manufacturing in particular. The operating mechanisms that govern the relationship between composition and grain size are interpreted using a model originally developed for aluminum and magnesium alloys and subsequently applied for titanium alloys. The prior beta grain factor observed and the interpretations of their correlations indicate that tungsten is a good grain refiner and such models are valid to explain the grain-refinement process. By extension, other binary elements or higher order alloy systems with similar thermophysical properties should exhibit similar grain refinement.

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Section: The High Level Of Interest In Additive Manufacturingmentioning

confidence: 99%

Microstructures and Grain Refinement of Additive-Manufactured Ti-xW Alloys

Mendoza

Samimi

Brice

et al. 2017

Metall Mater Trans A

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“…In order to understand the mechanisms underlying the grain refinement with different Mg concentration and intensive melt shearing, grain size data for both sheared and non-sheared TP-1 samples are plotted in Fig. 10 against the growth restriction factor Q. Parameters used to calculate growth restriction factor Q are adopted from references [10,48]. For the samples with intensive melt shearing, the grain size decreases only slightly with the increase of Q.…”

Section: Mechanisms Of Enhanced Heterogeneous Nucleationmentioning

confidence: 99%

“…On the other hand, the theoretical basis of the growth restriction theory is that restriction of the growth of already nucleated grains, permits further nucleation in the undercooled melt ahead of the solidification front, until the total latent heat release is sufficient to cause recalescence [8]. The growth restriction factor Q is often used as a measure of the solute effect on grain refinement in the absence of solute interactions [8][9][10][11][12][13][14]. Empirically, it was found that grain size can be described as a linear function of 1/Q [9].…”

Section: Introductionmentioning

confidence: 99%

Mechanisms of enhanced heterogeneous nucleation during solidification in binary Al–Mg alloys

Li¹,

Wang²,

Fan³

2012

Acta Materialia

177

120

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This paper investigates the mechanisms involved in the grain refinement of Al-Mg alloys through varying the Mg content and applying intensive melt shearing. It was found that the oxide formed in Al-Mg alloys under normal melting conditions is MgAl 2 O 4 , which displays an equiaxed and faceted morphology with {111} planes exposed as its natural surfaces. Depending on the Mg content, MgAl 2 O 4 particles exist either as oxide films in dilute Al-Mg alloys (Mg<1wt.%) or naturally dispersed discrete particles in more concentrated Al-Mg alloys (Mg>1wt.%). Such MgAl 2 O 4 particles can act as potent sites for nucleation of α-Al grains, which is evidenced by the well-defined cube-on-cube orientation relationship between MgAl 2 O 4 and α-Al. Enhanced heterogeneous nucleation in Al-Mg alloys can be attributed to the high potency of MgAl 2 O 4 particles with a lattice misfit of 1.4% and the increased number density of MgAl 2 O 4 particles due to either natural dispersion by the increased Mg content or forced dispersion through intensive melt shearing. It was also found that intensive melt shearing leads to significant grain refinement of dilute Al-Mg alloys by effective dispersion of the MgAl 2 O 4 particles entrapped in oxide films, but it has marginal effect on the grain refinement of concentrated Al-Mg alloys, where MgAl 2 O 4 particles have been naturally dispersed into individual particles by the increased Mg content.

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“…This characteristic feature of grain refinement and inoculation processes are called fading effects. That is why the so-called grain refiner and inoculants differ from microalloying, the effects of which are independent of time [11][12]. Literature provides limited data [11][12][13][14] on the primary structure -maximum undercooling relationship in the Al-5Cu system as a function of time (fading effects) lapsed from the grain refinement treatment.…”

Section: Introductionmentioning

confidence: 99%

“…That is why the so-called grain refiner and inoculants differ from microalloying, the effects of which are independent of time [11][12]. Literature provides limited data [11][12][13][14] on the primary structure -maximum undercooling relationship in the Al-5Cu system as a function of time (fading effects) lapsed from the grain refinement treatment. The purpose of this study was to investigate the effect of stability in modifying the primary structure -dendrites of α(Al) phase in the aluminum-copper type of alloys, using selected master alloys (1) Al-5%Ti-1%B, (2) Al-5%Ti and (3) Al-3%B as well as examining Brought to you by | MIT Libraries Authenticated Download Date | 5/11/18 7:08 AM the effect of the initial titanium content in the base alloy on the stability of these effects.…”

Section: Introductionmentioning

confidence: 99%

Effect of Titanium and Boron on the Stability of Grain Refinement of Al-Cu Alloy

Górny¹,

Sikora²,

Kawalec³

2016

Archives of Foundry Engineering

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The present research was conducted on thin-walled castings with 5 mm wall thicknesses. This study addresses the effect of the influence of different master alloys, namely: (1) Al-5%Ti-1%B, (2) Al-5%Ti and (3) Al-3%B, respectively on the structure and the degree of undercooling (ΔT α = T α -T min , where T α -the equilibrium solidification temperature, T min -the minimum temperature at the beginning of α(Al) solidification) of an Al-Cu alloy. The process of fading has been investigated at different times spent on the refinement treatment ie. from 3, 20, 45 and 90 minutes respectively, from the dissolution of master alloys. A thermal analysis was performed (using a type-S thermocouple) to determine cooling curves. The degree of undercooling and recalescence were determined from cooling and solidification curves, whereas macrostructure characteristics were conducted based on a metallographic examination. The fading effect of the refinement of the primary structure is accompanied by a significant change in the number (dimension) of primary grains, which is strongly correlated to solidification parameters, determined by thermal analysis. In addition to that, the analysis of grain refinement stability has been shown with relation to different grain refinements and initial titanium concentration in Al-Cu base alloy. Finally, it has been shown that the refinement process of the primary structure is unstable and requires strict metallurgical control.

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A model of grain refinement incorporating alloy constitution and potency of heterogeneous nucleant particles

Cited by 514 publications

References 20 publications

Microstructures and Grain Refinement of Additive-Manufactured Ti-xW Alloys

Microstructures and Grain Refinement of Additive-Manufactured Ti-xW Alloys

Mechanisms of enhanced heterogeneous nucleation during solidification in binary Al–Mg alloys

Effect of Titanium and Boron on the Stability of Grain Refinement of Al-Cu Alloy

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