Banca de DEFESA: JULIANO AUGUSTO MEDEIROS DE MENEZES E OLIVEIRA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : JULIANO AUGUSTO MEDEIROS DE MENEZES E OLIVEIRA
DATE: 30/11/2023
TIME: 08:00
LOCAL: REMOTO
TITLE:

Study of the effect of electropulsing on the mechanical and microstructural behavior of the AA7075 alloy (Al-Zn-Mg-Cu) for the self-healing of pre-deformed alloys

KEY WORDS:

self-healing, aluminium, AA7075, defects, damage mechanics, electropulsing

PAGES: 75
BIG AREA: Engenharias
AREA: Engenharia de Materiais e Metalúrgica
SUMMARY:

Over the past few years, research into self-healing materials has gained increasing scientific attention. In this class of bioinspired materials, engineers and scientists rely on biological mechanisms to design new materials with unique characteristics. Advances in this sense are widely noted in several classes of materials. Specifically for metallic materials processing by electrical pulses, or EPT (Electropulsing Treatment) is a new approach to self-healing that is growing in importance in the technological field. The application of a controlled current of sufficiently high density, but with a low temperature rise, generates a electron flow with energy capable of modifying the microstructure, which may promote stress relief, the reduction of microvoids and microcracks or even the recrystallization. Given the importance of techniques that increase the useful life of aeronautical components, the purpose of this work is to establish a methodology with the development of appropriate parameters for the self-repair process via electrical pulses in the aluminum alloy AA 7075 (Al-Zn-Mg -Cu). Compositional and phase analysis was performed via X-ray fluorescence (XRF) and X-ray diffraction (XRD). The mechanical behavior and generation of crystalline defects was previously evaluated in specimens machined according to the ASTM E8 standard, under interrupted tensile tests at deformations of 60%, 70%, 80%, 90% and 95% relative to rupture, resulting in the increase of yield stresses and reduction of ductility. The hardest samples (90 and 95% deformed) were treated via EPT with peak current (Ip) of 400 A and 500 A; base current 0 A (Ib), peak time (Tp) and base time in 0.1 s (Tb) in a total treatment time of 7s, 14s and 21s totaling 35, 70 and 105 25 cycles respectively. The deformed samples before and after EPT were analyzed by tensile tests, the results of which confirmed the increase in ductility and the reduction in yield stress with the longer period of applied current. The most critical condition, referring to samples deformed to 95% of rupture, treated by EPT (Ip of 400 A) with 7s, 14s and 21s were analyzed via residual stresses by XRD, proving the relief of residual stresses promoted by EPT due to the application period, in agreement with the behavior under tensile test. Despite the evidence supporting the effect of EPT on mechanical properties, surface analyzes of the specimens, via field emission scanning electron microscopy (SEM-FEG), were not sufficient to prove the microstructural effect of self-repair, requiring more detailed analyzes.

COMMITTEE MEMBERS:
Presidente - 1350249 - RUBENS MARIBONDO DO NASCIMENTO
Externo ao Programa - 1652765 - MAURÍCIO MHIRDAUI PERES - UFRNExterno ao Programa - 2414250 - MEYSAM MASHHADIKARIMI - UFRNExterno à Instituição - ALBERTO JORGE JUNIOR - UFSCAR
Externo à Instituição - AUGUSTO JOSE DE ALMEIDA BUSCHINELLI - UFSC