Investigation of the impacts of artificial ageing, re-ageing and cryogenic cycles on multiplex second phase precipitation and life-time prediction in 7075 alloy


ALTUNTAŞ G., ÖZDEMİR A. T., BOSTAN B.

Materials Today Communications, vol.40, 2024 (SCI-Expanded) identifier

  • Publication Type: Article / Article
  • Volume: 40
  • Publication Date: 2024
  • Doi Number: 10.1016/j.mtcomm.2024.109602
  • Journal Name: Materials Today Communications
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Compendex, INSPEC
  • Keywords: 7075 Al Alloy, Cryogenic process, Precipitation Kinetics, Retrogression and re-aging
  • Gazi University Affiliated: Yes

Abstract

In this study, artificial ageing, re-ageing and multiple levels of cryogenic treatments were practiced on 7075 aluminium alloy. Microstructural changes in the material as a result of the final cryogenic cycles were characterized by SEM and TEM, and the resulting phases with successive upsurge stages of nucleation sites were observed. Throughout crystallographic and X-ray analyses; dislocation densities, strain values of the planes, texture coefficient and plane orientations were determined. Micro-hardness measurements were also carried out to mechanically support the data attained from these characterization methods. According to the results, dislocation density and hardness values particularly after -40 °C cryogenic treatment, achieved the highest value. Heating rate and activation energy-based phase life time predictions against temperature, together with nucleation and growth rates of precipitates were evaluated by thermal analyses. Life time calculations pointed out that the -40 °C was the critical point of sub-zero progression where, the longest useful life expectancy at temperatures of between 80 °C and 300 °C could be reached out meticulously.