masterThesis
Microestrutura, parâmetros térmicos e citotoxicidade da liga hipoeutética Sn-2,0%Ag modificada com 0,2%Ni
Fecha
2022-07-11Registro en:
SOUSA, Raí Batista de. Microestrutura, parâmetros térmicos e citotoxicidade da liga hipoeutética Sn-2,0%Ag modificada com 0,2%Ni. 2022. 115f. Dissertação (Mestrado em Ciência e Engenharia de Materiais) - Centro de Ciências Exatas e da Terra, Universidade Federal do Rio Grande do Norte, Natal, 2022.
Autor
Sousa, Raí Batista de
Resumen
The addition of nickel (Ni) in tin-based alloys applied to microelectronic components has
received special attention in recent years. Ni promotes changes in mechanical strength,
toughness, creep resistance, and electrical properties. In this context, the present study aims to
understand the effect of Ni addition (0.2% by weight) on solidification thermal parameters (for
liquidus and eutectic isotherms: cooling rate-ṪL/ṪE and growth rate-VL/VE), microstructure,
microhardness and cytotoxicity of directionally solidified Sn-2%Ag (by weight) hypoeutectic
alloy under transient heat flow conditions. A wide range of microstructures were acquired via
optical (OM) and scanning electron microscopy (SEM), in addition to phase identification and
alloy element distribution throughout the Sn-Ag and Sn-Ag-Ni alloy castings, respectively. The
effect of Ni on mechanical properties was performed by Vickers microhardness test.
Cytotoxicity analyses (cell viability) were performed using Sn-Pb system alloys (Pb-10wt.%Sn
and Sn-20wt.%Pb) as reference. The addition of Ni in the Sn-2wt.%Ag alloy increased the
values of cooling rate (ṪL/ṪE) and growth rate (VL/VE), especially for the first positions from
the metal/mold interface. Thus, Ni caused a microstructural refinement of the dendritic structure
(λ2 and λ3), but without affecting the microstructural scale of the eutectic mixture. As-cast
microstructures for the Sn-2wt.%Ag and Sn-2wt.%Ag-0.2wt.%Ni alloys are completely
dendritic, formed by a Sn-rich matrix (β-Sn) surrounded by a eutectic mixture (β-Sn +Ag3Sn)
and (β-Sn +Ag3Sn + Ni3Sn4), respectively. Ag displayed inverse and normal-type
macrossegregation profiles for the binary and ternary alloys, respectively, while for Ni, there
was a slightly inverse-type profile. The addition of Ni seems to have stabilized the fibrous
morphology of Ag3Sn, so that Ag3Sn fibers were observed for cooling rates higher than those
reported in the literature. The increase in microhardness for the Sn-2wt.%Ag-0.2wt.%Ni alloy
occurred due to microstructural refinement and the presence of the Ni3Sn4 intermetallic.
Cytotoxicity analyses demonstrated that the microstructural scale does not affect the toxicity of
the alloys examined, but that incubation time and chemical composition are the main
influencing factors. The Pb-containing alloys showed higher levels of toxicity compared to SnAg and Sn-Ag-Ni alloys.