Banca de DEFESA: RAÍ BATISTA DE SOUSA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : RAÍ BATISTA DE SOUSA
DATE: 11/07/2022
TIME: 08:00
LOCAL: Sala virtual (videoconferência): https://meet.google.com/pam-wjps-xeo
TITLE:

Microstructure, Thermal Parameters and Cytotoxicity of the Ni-Modified Sn-2.0wt.%Ag Hypoeutectic Alloy

KEY WORDS:

Solidification; Sn-Ag-Ni alloys; Microstructure; Thermal Parameters; Cytotoxicity.

PAGES: 116
BIG AREA: Engenharias
AREA: Engenharia de Materiais e Metalúrgica
SUBÁREA: Metalurgia Física
SPECIALTY: Transformação de Fases
SUMMARY:

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-Ṫ_L/Ṫ_E and growth rate-V_L/V_E), 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 (Ṫ_L/Ṫ_E) and growth rate (V_L/V_E), 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 Sn-Ag and Sn-Ag-Ni alloys.

COMMITTEE MEMBERS:
Presidente - 2345599 - BISMARCK LUIZ SILVA
Externo ao Programa - 1652765 - MAURÍCIO MHIRDAUI PERES - UFRNExterno à Instituição - CLAUDIO ALVES DE SIQUEIRA FILHO