Influence of Annealing on Microstructural Evolution, Precipitation Sequence, and Fracture Toughness of Cryorolled Al-Cu-Si Alloy

Microstructural evolution, precipitation sequence, and fracture toughness of cryorolled Al 2014 alloy subjected to annealing treatment were investigated in the present work. Al 2014 alloy was solutionized (ST) and subjected to cryorolling (CR) up to effective true strain of 2.3. The CR Al 2014 alloy samples were annealed (AN) at temperatures ranging from 100 to 350 degrees C for the duration of 45 min. TEM and XRD studies of the CR and CR + AN were made to understand its precipitation kinetics. Fracture toughness tests were performed on CR and CR + AN alloy, and its deformation behavior was correlated with microstructural features. The improvement in fracture toughness K-ee (23.06-37.8 MPa root m) of CR Al 2014 alloy was observed as compared to ST alloy. The fracture toughness was retained up to 200 degrees C for CR alloy, but it started decreasing beyond 200 degrees C. The improvement in fracture toughness of cryorolled Al 2014 alloy at lowtemperature annealing from 100 to 200 degrees C is attributed to the formation of GP zones and metastable phase theta'. However, beyond temperature 200 degrees C, fracture toughness has reduced due to combined effect of recovery, recrystallization, and formation of stable coarser phase such as theta and lambda.