Banca de QUALIFICAÇÃO: BRUNO SILVA SOBRAL

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
STUDENT : BRUNO SILVA SOBRAL
DATE: 24/05/2021
TIME: 09:00
LOCAL: https://meet.google.com/fhm-drzz-wcf
TITLE:

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

KEY WORDS:

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

PAGES: 89
BIG AREA: Engenharias
AREA: Engenharia de Materiais e Metalúrgica
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 the addition of zinc (Zn) 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
Externo ao Programa - 1938946 - NICOLAU APOENA CASTRO