Banca de DEFESA: BRUNO SILVA SOBRAL

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : BRUNO SILVA SOBRAL
DATE: 27/09/2021
TIME: 14:00
LOCAL: Sala virtual (videoconferência): https://meet.google.com/svk-dcbz-myz
TITLE:

Directional Solidification of  Sn-3.5wt.%Ag-xZn alloys

KEY WORDS:

Directional solidification; Sn-Ag-Zn alloys; microstructure; cell/dendritic transition; microhardness.

PAGES: 95
BIG AREA: Engenharias
AREA: Engenharia de Materiais e Metalúrgica
SUBÁREA: Metalurgia Física
SPECIALTY: Transformação de Fases
SUMMARY:

Alloys of the Sn-Ag system are of interest to the electronic microcomponent industry, as they have superior mechanical properties to the alloys of the Sn-Pb system, as well as good wetting  in copper substrates and great fluency resistance and thermal fatigue. The microstructure of the eutectic Sn-3,5% Ag alloy solidified non-equilibrium consists of tin-rich dendrites (β-Sn) surrounded by an eutectic mixture Sn+Ag₃Sn, where the morphology of the Ag₃Sn intermetallic is controlled by the cooling rate. In this sense, this work aims to study the influence of Zn additions (0.5 and 1.0 wt%) in the thermal parameters such as cooling and growth rates (Ṫ_L/V_L-liquidus isotherm and Ṫ_E/V_E-eutectic front), microstructure and microhardness of the eutectic directionally solidified Sn-3.5wt.% Ag alloy  under unsteady state conditions. The samples were characterized by Optical Microscopy (MO), Scanning Electron Microscopy (SEM), X-Ray Fluorescence (FRX), X-Ray Diffraction (DRX) and Vickers Microhardness. The microstructure of the Sn-3.5wt.% Ag alloy is completely dendritic, composed of a Sn-rich matrix (β-Sn) surrounded by a eutectic mixture of the Sn and Ag₃Sn phases. On the other hand, the Zn-modified alloy with 1wt.% Zn exhibited a fully cellular eutectic microstructure, where its interior is formed by a mixture of the β-Sn, ε-Ag₃Sn and ζ-AgZn phases. The Sn-3.5wt.% Ag-1wt.% Zn alloy showed a cellular/dendritic transition to V_L= 1.15 mm/s and Ṫ_L= 8.55 °C/s. The decrease in the Ṫ and V values caused a coarsening of the dendritic and cellular eutectic arrangements. Additions of 0.5wt% and 1wt.% Zn promoted increases of 42.6% and 47.5% in hardness of the Sn-3.5wt.% Ag alloy, respectively.

BANKING MEMBERS:
Presidente - 2345599 - BISMARCK LUIZ SILVA
Externo ao Programa - 1652765 - MAURÍCIO MHIRDAUI PERES
Externa à Instituição - CLARISSA BARROS DA CRUZ - UFOP