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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Transient directional solidification of a eutectic Al-Si-Ni alloy: Macrostructure, microstructure, dendritic growth and hardness

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Author(s):
Kakitani, Rafael [1] ; Cruz, Clarissa B. [1] ; Lima, Thiago S. [1] ; Brito, Crystopher [2] ; Garcia, Amauri [1] ; Cheung, Noe [1]
Total Authors: 6
Affiliation:
[1] Univ Campinas UNICAMP, Dept Mfg & Mat Engn, BR-13083860 Campinas, SP - Brazil
[2] Sao Paulo State Univ UNESP, Campus Sao Joao da Boa Vista, BR-13876750 Sao Joao Da Boa Vista, SP - Brazil
Total Affiliations: 2
Document type: Journal article
Source: MATERIALIA; v. 7, SEP 2019.
Web of Science Citations: 3
Abstract

The Al-11 wt%Si-5 wt%Ni eutectic alloy was directionally solidified (DS) under transient heat flow conditions at cooling rates in a range of about 1-25 degrees C/s along the length of the casting. For comparison purposes binary Al-11 wt%Si and Al-5 wt%Ni alloys were also solidified under similar experimental conditions. Initially characterized by columnar grains, the macrostructure of the ternary DS alloy casting evolved during solidification to a columnar to equiaxed transition (CET) at critical cooling rates of about 1.3-1.6 degrees C/s, i.e. more than 7 times higher than the CET critical value determined in the literature for Al-Ni and Al-Si alloys. The microstructure of the ternary alloy casting is shown to be constituted by primary Si crystals and alpha-Al dendritic branches surrounded by the eutectic phase (alpha-Al+Si+Al3Ni), with the Al3Ni phase having initially a plate-like morphology, which with the decrease in the solidification kinetics, evolved to a fishbone morphology. The pertinent scaling laws representing the dendritic growth of the eutectic ternary alloy, properly compared to those of the examined Al-Si and Al-Ni binary alloys are outlined. The scale of the dendritic alpha-Al phase is shown to affect the Vickers hardness (HV) along the length of the ternary eutectic alloy casting, and a Hall-Petch type equation is proposed relating HV to the secondary dendritic arm spacing. (AU)

FAPESP's process: 17/15158-0 - Characterization of microstructure and properties in the evaluation of alloys for thermal interface contact
Grantee:Amauri Garcia
Support Opportunities: Regular Research Grants