Banca de QUALIFICAÇÃO: FREDERICO ZANON MARCHIONNI

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
STUDENT : FREDERICO ZANON MARCHIONNI
DATE: 08/09/2025
TIME: 15:00
LOCAL: Online - meet.google.com/bxf-xftx-ozx
TITLE:

ANALYSIS OF THE INFLUENCE OF DELTA FERRITE ON THE DUCTILE-BRITTLE TRANSITION OF WELDED JOINTS OF CHROMIUM-NICKEL AUSTENITIC STAINLESS STEEL

KEY WORDS:

Delta ferrite, AISI 304 stainless steel, ductile-to-brittle transition, Charpy impact test, GTAW welding, microstructure, fracture mechanics.

PAGES: 34
BIG AREA: Engenharias
AREA: Engenharia de Materiais e Metalúrgica
SUBÁREA: Metalurgia Física
SPECIALTY: Estrutura dos Metais e Ligas
SUMMARY:

The application of stainless steel in mechanical components operating at sub-zero temperatures is well established. Among the various manufacturing processes, welding is particularly significant. It is well known that during the thermal cycle of the welding process, delta ferrite is formed, predominantly within the fusion zone and the heat-affected zone. Evidence reported in the literature indicates that delta ferrite reduces the toughness of the material at elevated and ambient temperatures, in addition to promoting the precipitation of the sigma phase, which is highly undesirable due to its brittleness. Nevertheless, a knowledge gap remains regarding the behavior of delta ferrite in the microstructure of stainless steels when exposed to sub-zero temperatures. The present study investigates the influence of delta ferrite on the ductile-to-brittle transition of welded joints in austenitic Cr-Ni stainless steels. The objective is to elucidate how microstructural modifications—particularly the presence of delta ferrite—resulting from the Tungsten Inert Gas (TIG) welding process affect the impact resistance of the material at low temperatures. Experimental procedures will be conducted on 30 specimens, of which 15 will be tested in the as-welded condition and 15 after solution heat treatment. The toughness of the material will be assessed by means of Charpy impact testing at five different temperatures: -50 ºC, -30 ºC, -20 ºC, -10 ºC, and 0 ºC. Metallographic characterization will include optical microscopy (OM) for delta ferrite quantification and scanning electron microscopy (SEM) for fracture mode analysis. Após as análises dos resultados é esperado que a curva de transição dúctil-frágil seja mais acentuada e se desloque para a direita, ou seja, a zona frágil esteja mais maior nas peças com presença de ferrita delta. The findings of this study are expected to contribute to a deeper understanding of the mechanical behavior of welded stainless steel joints, providing valuable insights for applications that demand high structural reliability under cryogenic and sub-zero service conditions.

COMMITTEE MEMBERS:
Presidente - CINTHIA GABRIELY ZIMMER
Externo ao Programa - ALEXANDRE LUIS GASPARIN
Externa à Instituição - CAMILA DOS SANTOS TORRES - UFSM
Externo à Instituição - PEDRO HENRIQUE COSTA PEREIRA DA CUNHA