Enhanced heterogeneous nucleation in AZ91D alloy by intensive melt shearing

Fan, Z.; Wang, Y.; Xia, Ming; Arumuganathar, Sumathy

doi:10.1016/j.actamat.2009.06.052

Cited by 227 publications

(181 citation statements)

References 30 publications

Supporting

Mentioning

126

Contrasting

Order By: Relevance

“…More recently, Atamanenko et al [18] investigated the grain refining effect of exogenous oxides combined with ultrasonic treatment in pure Al (99.95%Al), and attributed the grain refinement to cavitation-induced heterogeneous nucleation through the activation of oxides. In addition, it has been demonstrated that, via the introduction of intensive melt shearing using the MCAST process, naturally occurring oxides in liquid Mg-and Al-alloys can be harnessed to enhance heterogeneous nucleation for microstructural refinement in Mg and Al alloys [19][20][21]. The enhanced heterogeneous nucleation was explained through the significantly increased number density of individual oxide particles by the strong dispersive power of intensive melt shearing [20].…”

Section: Introductionmentioning

confidence: 99%

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

Li¹,

Wang²,

Fan³

2012

Acta Materialia

Self Cite

177

120

View full text Add to dashboard Cite

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.

show abstract

Section: Introductionmentioning

confidence: 99%

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

Li¹,

Wang²,

Fan³

2012

Acta Materialia

Self Cite

177

120

View full text Add to dashboard Cite

show abstract

“…These oxide particles act as potent nucleating sites. [24] Two types of nucleation events were proposed during the solidification of intensive sheared liquid: [23] (1) forced wetting of oxide particles, which then act as a potent nucleating substrate for the matrix; and (b) multistep nucleation mechanism, where oxide nucleates intermediate compounds, which then nucleate the a-matrix. In addition, the intensive shearing provides the melt with uniform chemical composition.…”

Section: Grain Sizementioning

confidence: 99%

“…[15][16][17] These phases affect the rolling process and influence the final sheet properties. [6,7,18] The melt conditioning by advanced shearing technology (MCAST) process can be used to treat melts of aluminum and magnesium alloys under both semisolid [19,20] and fully liquid conditions [21][22][23][24][25] and can produce refined cast microstructures with significantly reduced segregation. In the present study, we examined the use of high shear melt conditioning on the tolerance of an AA5754 automotive sheet alloy to the addition of 0.6 wt pct Fe, 0.8 wt pct Si, and 0.5 wt pct Cu.…”

Section: Introductionmentioning

confidence: 99%

Influence of Intensive Melt Shearing on the Microstructure and Mechanical Properties of an Al-Mg Alloy with High Added Impurity Content

Kumar

Babu

Scamans

et al. 2011

Metall Mater Trans A

Self Cite

View full text Add to dashboard Cite

We have investigated the influence of melt conditioning by intensive shearing on the mechanical behavior and microstructure of Al-Mg-Mn-Fe-Cu-Si alloy sheet produced from a small book mold ingot with high added impurity content. The melt conditioned ingot has fine grains throughout its cross section, whereas a conventionally cast ingot, without melt shearing, has coarser grains and shows a wider variation of grain size. Both needle-shaped and coarse Chinese script iron bearing intermetallic particles are found in the microstructure at the center of the conventionally processed ingot, but for the melt conditioned ingot, only fine Chinese script intermetallic particles are observed. In addition to the iron bearing intermetallics, Mg 2 Si particles are also observed. The ingots were rolled to thin sheet and solution heat treated (SHT). During rolling, the iron-based intermetallics and Mg 2 Si particles are broken and aligned along the rolling direction. Yield strength (YS), ultimate tensile strength (UTS), and elongation of the intensively melt sheared and processed sheet are all improved compared to the conventionally cast and processed sheet. Fractographic analysis of the tensile fracture surfaces shows that the clustered and coarse iron bearing intermetallic particles are responsible for the observed reduction in mechanical properties of the conventionally cast sheet. We have shown that by refining the initial microstructure of the ingot by intensive shear melt conditioning, it is possible to achieve improved mechanical properties at the final sheet gage of an AlMgMn alloy with a high content of impurities.

show abstract

“…[26] These oxide particles then act as potent nucleating sites to enhance heterogeneous nucleation during solidification, which has been confirmed experimentally. [26] The current experimental results showed clearly that the melt conditioning technique prior to TRC improved the overall quality of the resultant AZ31 magnesium alloy strip substantially. The results revealed also that the refined and uniform microstructure of the MCTRC strip had a strong, positive influence on downstream processing and mechanical properties at final gauge.…”

Section: Discussionmentioning

confidence: 74%

“…[24,25] Most importantly, effective grain refiners are still sought for magnesium alloys with aluminum additions such as the AZ and AK series, although proven chemical refiner additions, e.g., zirconium, are available for aluminum-free magnesium alloys. [26,27] Electromagnetic fields can be used to modify material convection in the solidification zone, but this process is difficult to control. [28] Physical melt treatment is an alternative option and melt conditioning by intensive shear prior to solidification has been developed for this purpose.…”

Section: Introductionmentioning

confidence: 99%

The Impact of Melt-Conditioned Twin-Roll Casting on the Downstream Processing of an AZ31 Magnesium Alloy

Bayandorian

Huang

Fan

et al. 2011

Metall Mater Trans A

Self Cite

View full text Add to dashboard Cite

Melt conditioning by intensive shear was used prior to twin-roll casting of AZ31 magnesium alloy strip to promote heterogeneous nucleation and to provide a refined and uniform microstructure without severe macrosegregation. The cast strip was then processed by homogenization, hot rolling, and annealing, and its downstream processing was compared with a similar cast strip produced without melt conditioning. Melt conditioning produced strip with accelerated kinetics of recrystallization during homogenization and improved performance in hot rolling and improved tensile properties. An average tensile elongation of~28 pct was achieved, which is substantially higher than the~9 pct obtained for the strip produced without melt conditioning which is consistent with reported values (~6 pct to 16 pct). The as-cast, homogenized, and hot-rolled microstructures of the strip were characterized. The kinetics of homogenization and hot-rolling process have been discussed in detail.

show abstract

Enhanced heterogeneous nucleation in AZ91D alloy by intensive melt shearing

Cited by 227 publications

References 30 publications

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

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

Influence of Intensive Melt Shearing on the Microstructure and Mechanical Properties of an Al-Mg Alloy with High Added Impurity Content

The Impact of Melt-Conditioned Twin-Roll Casting on the Downstream Processing of an AZ31 Magnesium Alloy

Contact Info

Product

Resources

About