Thermodynamic investigation on phase formation in the Al-Si rich region of Al-Si-Ti system

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalNot applicablepeer-review

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Author(s)

  • Yang Li
  • Qin-Fen Gu
  • Qun Luo
  • Yuepeng Pang
  • Shuang-Lin Chen
  • Kuo-Chih Chou
  • Qian Li

Detail(s)

Original languageEnglish
Pages (from-to)78-90
Journal / PublicationMaterials and Design
Volume102
Online published11 Apr 2016
Publication statusPublished - 15 Jul 2016

Abstract

The thermodynamic condition for phase formation in the Al-Si-Ti system is crucial for understanding the reason behind deteriorations of grain refinement and castability of Al-Si-Ti alloys. Seven Al-Si-Ti alloys annealed between 550 and 650 °C were used to clarify the inconsistencies of phase equilibria in the Al-Si rich region. The existences of τ1 (Zr3Al4Si5-type tetragonal), τ2 (ZrSi2-type orthogonal) and the three-phase equilibrium of τ1 + α-Al + Si were confirmed. Combined with a critical review of literature data, a CALPHAD-type thermodynamic description was developed for the phase equilibria in the Al-Si rich region of the Al-Si-Ti system between 550 and 900 °C. Meanwhile, edge-to-edge matching analysis according to the crystal structures of τ1 and τ2 shows that their nucleation efficacies for α-Al are both weaker than that of Ti(Al,Si)3. From the calculated phase equilibrium of L + τ2 + Ti(Al,Si)3 at 727 °C and the local equilibrium principle, τ2 would form on the surface of TiAl3 particle and deteriorate its grain refinement efficiency for α-Al. From the calculated liquidus projection, Ti(Al,Si)3 is the primary phase within 0-10.3 wt.% Si and 0.08-0.30 wt.% Ti. To avoid the formation of τ1 and τ2 for retaining good grain refinement efficiency and castability, a Ti/Si threshold was determined by thermodynamic calculations.

Research Area(s)

  • Aluminum alloys, CALPHAD, Grain refinement, Phase diagram, Ti/Si threshold

Citation Format(s)

Thermodynamic investigation on phase formation in the Al-Si rich region of Al-Si-Ti system. / Li, Yang; Gu, Qin-Fen; Luo, Qun; Pang, Yuepeng; Chen, Shuang-Lin; Chou, Kuo-Chih; Wang, Xun-Li; Li, Qian.

In: Materials and Design, Vol. 102, 15.07.2016, p. 78-90.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalNot applicablepeer-review