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

Autor(es)

Kakitani, Rafael ^[1] ; Cruz, Clarissa B. ^[1] ; Lima, Thiago S. ^[1] ; Brito, Crystopher ^[2] ; Garcia, Amauri ^[1] ; Cheung, Noe ^[1]

Afiliação do(s) autor(es)

^[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

• Tipo de documento: Artigo Científico
• Fonte: MATERIALIA; v. 7, SEP 2019.
• Citações Web of Science: 3

Resumo

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)

• Processo FAPESP: 17/15158-0 - Caracterização microestrutural e de propriedades na avaliação de ligas para contato térmico interfacial
• Beneficiário: Amauri Garcia
• Linha de fomento: Auxílio à Pesquisa - Regular