Heat-flow parameters affecting microstructure and mechanical properties of Al–Cu and Al–Ni alloys in directional solidification: an experimental comparative study
Author:
Júnior Paulo Felipe1ORCID, de Olivé Ferreira Leonardo2, Garção Wysllan Jefferson Lima3, de Paula Almeida Rangel1, Melo Camilla Mota1, Ferreira Alexandre Furtado1
Affiliation:
1. Graduate Program on Metallurgical Engineering , Universidade Federal Fluminense , Volta Redonda , Brazil 2. Aerospace Engineering Group , Universidade Federal do ABC , São Bernardo do Campo , Brazil 3. Federal Institute of Rio de Janeiro , Volta Redonda , Brazil
Abstract
Abstract
A comparative analysis was carried out of the alloys examined, using the results found for thermal variables, macrostructure, dendrite arm spacing, modulus of elasticity and microhardness. Comparing all the results for variables, a predominance was found of higher values for the Al-5.0 wt.% Cu alloy in relation to those for the Al-5.0 wt.% Ni alloy. Although structural transition has occurred in both alloys, the columnar–equiaxed transition position in castings was not altered during the solidification experiments. Addition of Ni solute into pure aluminum favors a significant decrease in tertiary dendrite spacing, while Cu addition leads to a coarser microstructure. Primary dendrite arm spacing, also, was measured along the castings of both alloys. Theoretical approaches such as the well-known Hunt–Lu, Bouchard–Kirkaldy, and Kurz–Fisher models were used to determine quantitatively this particular microstructural parameter. Good agreement was observed between experimental data and predictions by Hunt–Lu and Bouchard–Kirkaldy models, which assume solidification under a transient heat-flow condition. Finally, empirical equations relating tertiary dendritic arm spacing and mechanical properties to the scale of the dendritic microstructure have been proposed. While no relationship was observed between modulus of elasticity and tertiary dendritic arm spacing, addition of Cu into pure aluminum as an alloying element favored a reduction in the average value of modulus of elasticity when compared with those observed for the Al–Ni alloy. It was found that the microhardness decreases with increasing tertiary dendritic arm spacings. On the other hand, solute addition of Cu into commercially pure aluminum favors a microhardness higher than that verified during upward unidirectional solidification of the Al-5.0 wt.% Ni alloy.
Funder
Universidade Federal Fluminense
Publisher
Walter de Gruyter GmbH
Subject
Materials Chemistry,Metals and Alloys,Physical and Theoretical Chemistry,Condensed Matter Physics
Reference39 articles.
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