Análise fractográfica da liga AA 7075-T6 submetida à fadiga na condição de tratamento RRA e nitretada a plasma

Materia

article

Elisa Gombio Rocha¹  Maria Gabriela Galvão Camarinha¹  Danieli Aparecida Pereira Reis¹ 

[1] Universidade Federal de São Paulo

关键词: Fractography;    Fatigue;    Plasma Nitriding;    RRA;    7075-T6;   

DOI  :  10.1590/1517-7076-RMAT-2022-0305

学科分类：工程和技术（综合）

来源: Universidade Federal do Rio de Janeiro * Coordenacao dos Programas de Pos-Graduacao de Engenharia

【 摘 要 】

This work assessed the fracture behavior of the AA7075-T6 aluminum alloy subjected to fatigue loading. Both the notched and unnotched specimens underwent a retrogression heat treatment and re-aging (RRA) and plasma nitriding before the mechanical tests. Plasma nitriding, which has been a method chosen to increase the surface hardness and the fatigue, wear and corrosion resistances of various alloys was carried out with an active screen with a 20 Hz DC source and a 40 Hz duty cycle. The RRA treatment, which is used to increase the strength and hardness of AA7075 aluminum alloy and obtain improvements in the fatigue and corrosion behaviors, was performed at 200 °C for 20 minutes with water cooling (resolubilization), followed by 24 hours at 120 °C (re-aging). The axial fatigue tests of notched and unnotched specimens were carried out with R = 0.1, frequency of 14 Hz, and at stress level of 150 MPa for notched specimens, and 500 MPa for unnotched specimens. The fatigue fracture was then performed via stereomicroscopy and scanning electron microscopy. For the unnotched specimens, AA7075-T6 and AA7075-RRA conditions presented similar fracture features, with good definition of the three stages of fatigue failure; the AA7075 nitrited condition presented no evidence of typical fatigue fracture. The notched specimens presented fractographies similar to the severe stress concentration condition, with surface marks convex to the nucleation region.

【 授权许可】

CC BY