Abstract :
To study the reponse of precipitation hardenable alloys of Al-Cu-Mg and Al-Li-Cu-Mg system to artificial ageing, a series of ternary and quaternery Al-alloys were used in the present investigation of thermal analyses. Samples supplied in the form of rolled sheets are fully recrystallised after solution treatment at 803 K for 1.2x10^3 sec and water quenching to 298 K. Alloys were aged artificial at the temperature 463 K. By using Differential Scanning Calorimetry (DSC) in the temperature range of (298–573) K, Differential Thermal Analyses (DTA) in the temperature range of (298–873) K together with Vickers hardness measurements, the response of the alloys used in the present study to artificial ageing were investigated. It was observed that in Al-Cu-Mg and 0.07wt%Li containing Al-Cu-Mg alloys, GPB(Cu,Mg) zones do form during water quenching at 298 K following solutionising heat treatment. Artificial ageing (AA) at 463 K up to 1,8x10^4 sec, result in GPB(Cu,Mg) zones dissolution causing a decrease in hardness values. For 1,72x10^5 sec of AA in the alloys cause S/(Al2CuMg) precipitation as condiered by DTA/DTK analyses, resulting in an increase in hardness values. Lithium additions up to 0,75 wt %Li, cause T1(Al2CuLi) and T2(Al6CuLi) phase formation together with S/- precipitation as DTA/DTK analyses show after the same AA treatment. Then, the phases of the corrosion behavior of artificially aged samples were examined.
NaturalLanguageKeyword :
Al , Li Alloys , Artificial Age , Thermal Analysis , Hardenes , Corrosion
