Ref.: EmaEgp23-001
Apresentador: Carolina Moreira de Almeida
Autores (Instituição): Ferreira, A.F.(Universidade Federal Fluminense); Sales, R.C.(Universidade Federal Fluminense); Garção, W.J.(Instituto Federal do Rio de Janeiro); Nascimento, M.C.(Universidade Federal Fluminense); Baptista, L.A.(Universidade Federal Fluminense); Almeida, C.M.(Universidade Federal Fluminense);
Resumo:
The addition of bismuth solute in a hypoeutectic binary Al - 4 wt.% Cu alloy is discussed in terms of its thermal parameters, formation of macrostructure, microstructure, microsegregation and microhardness. These materials were investigated during the upward unidirectional solidification under transient heat flow condition. Differences in thermal parameters of solidification, macrostructural and microstructural patterns, microsegregation and microhardness were observed and systematically discussed. From experimental results concerning thermal parameters of the binary Al - 4.0 wt.% Cu and ternary Al - 4.0 wt.% Cu – 2.0 wt.% Bi alloys, it can be concluded that said parameters are strongly affected by position along the casting length and addition of bismuth solute. A dendritic structure was observed in both alloys analyzed. For binary alloy, due to solidification processing conditions imposed during experiment, a columnar macrostructure prevailed along casting, while for ternary alloy, can be observed a predominance of an equiaxed macrostructure. Experimental laws relating tertiary dendritic arm spacing (?3) to the solidification thermal parameters have been determined, which indicated that the increase in thermal parameters and bismuth addition, have favored a refinement effect on dendritic morphology. The results for concentration solutes, confirmed that microsegregation curves were influenced by solidification speed in both alloys analyzed, i.e., the curves were shown to move upward with the increase in solidification speed. The results of ternary alloy, show that microsegregation curves of Cu solute are also affected by addition of bismuth. The effects of the thermal parameters and bismuth addition on the microhardness were investigated. The values of this property decreased along the castings. These results have pointed out that microhardness is affected by both thermal parameters and addition of bismuth solute.