HTM ›› 2020, Vol. 45 ›› Issue (2): 61-65.DOI: 10.13251/j.issn.0254-6051.2020.02.012

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Formation mechanism of W(Al8Cu4Sc) phase in Al-Cu-Li-Sc alloy with high Cu content

Kong Debin, Li Caiqiong   

  1. College of Engineering, Yantai Nanshan University, Yantai Shandong 265713, China
  • Received:2019-08-25 Online:2020-02-25 Published:2020-04-03

Abstract:

The microstructural evolution of an Al-2.35Cu-4.6Li-0.12Sc(at%) alloy with high Cu content and the formation mechanism of W(Al8Cu4Sc) phase during homogenization were studied by means of OM、SEM、EPMA、XRD and STEM. The results show that the main solidification phase is TB (Al7Cu4Li) phase in as-cast, and Sc mainly exists in the form of supersaturated solid solution. After homogenization, the TB phase dissolves completely, the content of Cu in the matrix increases and that of Sc decreases, the stable W phase forms at the same time. The analysis shows that the interface of TB phase and Al matrix must be a preferred nucleation site for the W phase because of the incoherent interface of TB phase and Al matrix. So the W phase nucleates preferentially here, and then transforms into the stable phases with a size of 1 μm by consuming the Sc atoms fixed in the supersaturate solid solution and Cu atoms in TB phase.

Key words: Al-Cu-Li alloy, Sc, W phase, microstructure

CLC Number: