Origin of the equiaxed zone in small ingots

Biloni, H.; Chalmers, B.

doi:10.1007/bf00585481

Cited by 51 publications

(28 citation statements)

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“…9) On the other hand, the cooling rate of permanent mold casting is about 50 Ks À1 . The singleroll method hinders movement of the solute elements, so diffusionless solidification (G L > G S ) schematically exhibited in free-energy composition diagram occurs [9][10][11] and therefore, provably prevents manganese compounds from precipitating. The result of XRD proved the ribbon to be single-phase magnesium solid solution.…”

Section: Experimental Conditionsmentioning

confidence: 99%

Observation of Manganese-Bearing Particles in Molten AZ91 Magnesium Alloy by Rapid Solidification

et al. 2003

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Magnesium alloy AZ91 contains 0.1 to 0.3 mass% manganese as an alloying element. Such manganese always reacts with aluminum and produces various compounds. Actually, numerous Mn-bearing particles are visible in polished surfaces under an optical microscope. Some Mnbearing particles are also expected to be present in molten alloy. We believe that some Mn-Al compounds are closely related to the superheating effect. However, it is not clear specifically what compounds exist in molten alloy and how contribute to grain refinement by superheating. In order to study this subject, we utilized a diffusionless process based on rapid solidification. Two grams of AZ91 alloy was melted in a stainless steel tube and then injected onto a copper wheel rotating at high-speed under various conditions to obtain cast ribbons. Cast ribbon was analyzed by an X-ray diffractometer, an electron probe micro-analyzer and a transmission electron microscope. These analyses indicated that the cast ribbons consist of single phase and that the structure is quite homogeneous, i.e., diffusionless solidification occurs due to rapid cooling. Manganese-bearing particles completely disappear in the melt around 963 K and superheat temperatures, which is inconsistent with presently accepted superheat mechanisms, the temperature-solubility nucleation theory and the temperature-phase relationship theory. In the meantime, cross-shaped Mn-bearing particles are often observed in the ribbons when the melt is cooled from superheat temperatures to the injecting temperature (973 K) before injecting. This treatment may facilitate the formation of these particles.

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Section: Experimental Conditionsmentioning

confidence: 99%

Observation of Manganese-Bearing Particles in Molten AZ91 Magnesium Alloy by Rapid Solidification

et al. 2003

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“…It was observed, however, that the solute concentration in rapidly solidified alloy materials could deviate from the value of the equilibrium phase diagram [17]. In a chill casting of molten Al-Cu binary alloys [18], the Cu concentration in the solid phase was found to be the same as the initial melt composition although the corresponding k e is about 0.17. In a splat quenching of Zn-Cd alloys [19], solid compositions higher than the maximum solid solute solubility of Zn rich Zn-Cd alloy were observed.…”

Section: Early Interesting Observation Of Solute Trapping In Rapid Somentioning

confidence: 95%

Phase-field investigation on the non-equilibrium interface dynamics of rapid alloy solidification

Choi

2011

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“…Then, predendrites extended from the discs radially, and finally dendrites grew in the preferred orientation. They 9) also measured the copper content in the disc of the Al0.6 mass% Cu alloy specimen poured on a copper chill block, and detected a higher copper content, close to the average content in the alloy, at the center of the disc. From this result, they 9) supposed that the discs were formed by a nondiffusional process.…”

Section: Introductionmentioning

confidence: 98%

“…They 9) also measured the copper content in the disc of the Al0.6 mass% Cu alloy specimen poured on a copper chill block, and detected a higher copper content, close to the average content in the alloy, at the center of the disc. From this result, they 9) supposed that the discs were formed by a nondiffusional process. In addition, Prates and Biloni 10) examined the effect of the casting conditions on the formation of the discs in AlCu alloy specimens, and found that the disc density monotonically increased with increasing surface roughness of the chill block, in proportion to the square of the heat transfer coefficient.…”

Section: Introductionmentioning

confidence: 98%

“…Biloni and Chalmers 9) observed the initially solidified structures on the bottoms of the AlCu alloy and the PbSn alloy specimens, and found that when the molten alloy was poured on the permanent mold, discs were formed on the surface of the specimen. Then, predendrites extended from the discs radially, and finally dendrites grew in the preferred orientation.…”

Section: Introductionmentioning

confidence: 99%

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Influence of Casting Conditions on Initially Solidified Structures Formed during Permanent-Mold Casting of Zn–Al and Al–Cu Alloys

Katô

Nakahara

2013

Mater. Trans.

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Molten Zn2.54 mass% Al (the Zn2Al) and Al2.35 mass% Cu (the Al2Cu) alloys were poured on the copper chill block to obtain initially solidified structures on the bottom of the specimen. The Zn2Al alloy poured on the chill block polished with emery paper formed discs that protruded about 1 µm from the bottom of the alloy specimen, as the case of the Al2Cu alloy. From the discs, predendrites that forms a cellular structure extended radially, and then dendrites grew outside the predendrites in the preferred orientation. The solute content had a local maximum at the center of the disc, which suggests that the solidification began from undercooled liquid. The orientation of the discs formed on the bottom of the Zn2Al ally specimen was [0 0 0 1] direction, but the discs formed on the bottom of the Al2Cu alloy specimen did not show a specific orientation. With increasing surface roughness of the polished chill block, the disc diameter increased but the areal number density of discs decreased. Furthermore, with increasing pouring temperature, the disc diameter and the areal number density of discs both increased. For a buffed chill block, however, no disc appeared for the Zn2Al alloy specimen but fine dendrites appeared on the bottom. In contrast, large discs formed on the bottom of the Al2Cu alloy. In particular, when the molten Al2Cu alloy was poured at 800°C or higher on the buffed chill block, two types of discs appeared on the bottom: normal discs of 20 to 30 µm in diameter, and very large discs (superdiscs) of 100 to 200 µm in diameter. Following these results, the formation process of the initially solidified structure is discussed.

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Origin of the equiaxed zone in small ingots

Cited by 51 publications

References 1 publication

Observation of Manganese-Bearing Particles in Molten AZ91 Magnesium Alloy by Rapid Solidification

Observation of Manganese-Bearing Particles in Molten AZ91 Magnesium Alloy by Rapid Solidification

Phase-field investigation on the non-equilibrium interface dynamics of rapid alloy solidification

Influence of Casting Conditions on Initially Solidified Structures Formed during Permanent-Mold Casting of Zn–Al and Al–Cu Alloys

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Origin of the equiaxed zone in small ingots

Cited by 51 publications

References 1 publication

Observation of Manganese-Bearing Particles in Molten AZ91 Magnesium Alloy by Rapid Solidification

Observation of Manganese-Bearing Particles in Molten AZ91 Magnesium Alloy by Rapid Solidification

Phase-field investigation on the non-equilibrium interface dynamics of rapid alloy solidification

Influence of Casting Conditions on Initially Solidified Structures Formed during Permanent-Mold Casting of Zn&ndash;Al and Al&ndash;Cu Alloys

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Influence of Casting Conditions on Initially Solidified Structures Formed during Permanent-Mold Casting of Zn–Al and Al–Cu Alloys