Microstructural evolution of solid-solution-treated Zn-22Al in the semisolid state

M. A M Arif, Mohd. Zaidi Omar, Norhamidi Muhamad, J. Syarif, P. Kapranos

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

The effect of solid-solution-treatment on the semisolid microstructure of Zn-22Al with developed dendrites was investigated. Forming Zn-22Al products by semisolid metal processing offers significant advantages, such as reductions in macro-segregation, porosity and forming costs. Thermal and microstructural analyses of the formed Zn-22Al alloy were performed by differential scanning calorimetry, scanning electron microscopy and optical microscopy. The changes in the microstructures and phase transformation in response to various solid-solution-treatments were analysed. In this study, as-cast samples were held isothermally at 330°C for 0.5-5h and then partially remelted at a semisolid temperature of 438°C for 1h to produce a solid-globular grain structure in a liquid matrix. A non-dendritic semisolid microstructure could not be obtained when the traditionally cast Zn-22Al alloy with developed dendrites was subjected directly to partial remelting. After solid-solution-treatment at 330°C, the black interdendritic eutectics were dissolved, and the dendritic structures gradually transformed into uniform β structures when the treatment time was increased. The coarsened and merged dendrites were separated as a result of penetration by the liquid phase and melting of the residual eutectic at sites along the former grain boundaries. The microstructure of the solid-solution-treated sample transformed into a small globular structure; the best shape factor of 0.9, corresponding to a particle size of 40±16μm, is achieved when the sample was treated for 3h followed by direct partial remelting into its semisolid zone.

Original languageEnglish
Pages (from-to)765-774
Number of pages10
JournalJournal of Materials Science and Technology
Volume29
Issue number8
DOIs
Publication statusPublished - Aug 2013

Fingerprint

Microstructural evolution
Solid solutions
Remelting
Microstructure
Eutectics
Dendrites (metallography)
Crystal microstructure
Liquids
Optical microscopy
Macros
Differential scanning calorimetry
Grain boundaries
Melting
Porosity
Phase transitions
Metals
Particle size
Scanning electron microscopy
Processing
Costs

Keywords

  • Dendritic
  • Liquidus
  • Semisolid metal processing
  • Solidus
  • Spherical morphologies

ASJC Scopus subject areas

  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys
  • Materials Chemistry
  • Mechanics of Materials
  • Mechanical Engineering

Cite this

Microstructural evolution of solid-solution-treated Zn-22Al in the semisolid state. / Arif, M. A M; Omar, Mohd. Zaidi; Muhamad, Norhamidi; Syarif, J.; Kapranos, P.

In: Journal of Materials Science and Technology, Vol. 29, No. 8, 08.2013, p. 765-774.

Research output: Contribution to journalArticle

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