Microestrutura, parâmetros térmicos e citotoxicidade da liga hipoeutética Sn-2,0%Ag modificada com 0,2%Ni

• Ano de defesa: 2022
• Autor(a) principal: Sousa, Raí Batista de
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal do Rio Grande do Norte; Brasil; UFRN; PROGRAMA DE PÓS-GRADUAÇÃO EM CIÊNCIA E ENGENHARIA DE MATERIAIS
• Palavras-chave em Português: Solidificação; Ligas Sn-Ag-Ni; Microestrutura; Parâmetros térmicos; Citotoxicidade; CNPQ::ENGENHARIAS::ENGENHARIA DE MATERIAIS E METALURGICA
• Link de acesso: https://repositorio.ufrn.br/handle/123456789/49233

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.