Unidirectional solidification of Zn-rich Zn–Cu peritectic alloys—I. Microstructure selection

• Published in: Acta materialia 2000-01, Vol.48 (2), p.419-431
• Main Authors: Ma, D., Li, Y., Ng, S.C., Jones, H.
• Format: Article
• Language: English
• Subjects: Alloys; Applied sciences; BRIDGMAN METHOD; CONCENTRATION RATIO; COPPER ALLOYS; Cross-disciplinary physics: materials science; rheology; CRYSTAL-PHASE TRANSFORMATIONS; DENDRITES; Exact sciences and technology; MATERIALS SCIENCE; Metals. Metallurgy; MICROSTRUCTURE; Peritectic solidification; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Phase transformations; Physics; SOLIDIFICATION; ZINC ALLOYS
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/S1359-6454(99)00365-1

A solidification microstructure selection diagram has been determined for Zn-rich Zn–Cu peritectic alloys containing up to 7.37 wt% Cu over the growth velocity range 0.02–4.82 mm/s and at a temperature gradient of 15 K/mm by means of the Bridgman technique. Regular and plate-like cellular growth was observed in a range of composition near the peritectic point at growth velocities above 0.5 mm/s. The minimum growth velocity for the formation of plate-like cellular growth was about 2.64 mm/s in the compositional range from 2.17 to 4.94 wt% Cu. Two transitions, namely, arrayed to nonaligned growth of primary dendrites, and peritectic to non-peritectic reaction, were also characterized and analyzed. The transition velocity from arrayed to nonaligned growth of primary dendrites increased with increasing alloy concentration, which is consistent with the prediction of a modified Hunt model. The transition growth velocity from peritectic to non-peritectic reaction exhibited a maximum near the peritectic composition.