Banca de QUALIFICAÇÃO: LINDOLPHO SALES DANTAS DA COSTA LIMA

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
DISCENTE : LINDOLPHO SALES DANTAS DA COSTA LIMA
DATA : 01/08/2019
HORA: 09:00
LOCAL: Sala de aulas do PPGCEM
TÍTULO:

DEVELOPMENT OF PHASE'S QUANTIFICATION METHOD IN DUAL PHASE BY EBSD

PALAVRAS-CHAVES:

Dual Phase; EBSD; pattern quality, MA; Threshold, deconvolution, repeatability.

PÁGINAS: 76
GRANDE ÁREA: Engenharias
ÁREA: Engenharia de Materiais e Metalúrgica
RESUMO:

Dual Phase steels are advanced high strength steels widely used in the automotive industry. The microstructure is based on martensite-austenite (MA) islands, dispersed in a ferrite matrix, its properties are high mechanical strength and good deformability. These features are differential in the automobile’s applications, because provide improve toughness and safety to the vehicle, as well as weight and fuel consumption reduction. Dual Phase steels are commonly characterized by optical microscopy (OM). The quantification of these phases, in general, occurs through the binarization of the image obtained by OM. However, the evaluation of these steels by OM presents problems related to the contrast between the phases, because one of its most used reagent (LePera) has a high oxidative power and reveal wrong microstructures after the attack. Characterization, in Dual Phase steels, using electron backscattered diffraction (EBSD) has been used more frequently, mainly using the pattern quality (PQ) analysis. In this paper, the EBSD PQ technique was used with the OM technique to develop a method to quantify Dual Phase steels by EBSD. For this, the microstructure and the second constituent’s fraction were compared, using Dual Phase steels submitted to different soaking temperatures (720 ° C, 740 ° C and 760 ° C), previously obtained by LIMA (2018). Thus, it was observed an evolution in the second constituent’s fraction, caused by the increase of the soaking temperature, in both methods. However, the quantification results showed the Threshold MA quantification method by Threshold attributed by the deconvolution's intersection standard, by the EBSD, showed the most representative MA values, because their values were not distant as the quantification by the area calculation of deconvolved histogram method. Furthermore, the intersection method was superior to the MA quantification method using arbitrary Threshold thought EBSD and OM, once there are not errors’ accumulation linked to the repeatability of the MA fractions, compared to these methods.

MEMBROS DA BANCA:
Presidente - 2266607 - FABIO JOSE PINHEIRO SOUSA
Externo ao Programa - 1652765 - MAURÍCIO MHIRDAUI PERES
Externo ao Programa - 1938946 - NICOLAU APOENA CASTRO