Melting and solidification characteristics of Zr-, Ni-, and Mn-containing 354-type Al-Si-Cu-Mg cast alloys

ABSTRACT

This study investigated the effects of adding Zr, as a base alloying element, besides Ni and Mn in different amounts and combinations on the melting and solidification characteristics of 354-type Al-Si-Cu-Mg alloys. Differential scanning calorimetry (DSC) was used to characterise the sequence of reactions occurring during the heating and/or cooling cycles; whereas scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) techniques were used to observe and identify existing intermetallic phases. Nickel proved to have a retarding effect on the kinetics of precipitation of the α-Al network and the eutectic Al-Si structure. Also, the presence of Ni consumed a considerable amount of Cu to form Al-Cu-Ni particles instead of Al₂Cu particles. Results revealed that solution treatment at 495°C for 5 h was sufficient to dissolve a large amount of Al₂Cu particles in the α-Al matrix, which is mandatory for a successful aging treatment of the alloys studied. Additions of these transition elements produced new intermetallic phases such as (Al,Si)₃(Ti,Zr), (Al,Si)₃Zr, Al₉FeNi, Al₃Ni, Al₃CuNi, and Al₉FeSi₃Ni₄Zr, in addition to the other phases, namely α-Al, eutectic silicon, Al₂Cu, Mg₂Si, Q-phase (Al₅Cu₂Mg₈Si₆), commonly observed in 354-type alloys, and Fe-based intermetallic phases including β-Al₅FeSi, α-Al₁₅(Fe, Mn)₃Si₂, and π-Al₈FeMg₃Si_6. Superheating the melt at 800°C instead of 750°C had an advantageous effect in that Al₃Zr particles originating from the Al-15%Zr master alloy were dissolved and hence coarse Zr-containing particles were barely spotted in the microstructures examined.

KEYWORDS:

• Al-Si-Cu-Mg alloy
• DSC analysis
• transition element additions
• precipitation
• dissolution
• SEM

Acknowledgments

The authors would like to thank Prof. A.M. Samuel for editing the text of this article.

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability

The raw data for reproducing the findings listed in this article cannot be shared now because it is a part of an ongoing PhD study.