Effects of Multiple Strengthening Treatments on Mechanical Properties and Stability of Nanoscale Precipitated Phases in an Aluminum-Copper-Lithium Alloy
S. Ahmadi, H. Arabi, A. Shokuhfar
1) Department of Material Science, Faculty of Engineering, Tarbiat Modares University, Tehran, Iran
2) Center of Excellence of Advanced Materials and Processing (CEAMP), Department of Metallurgy and Materials Science and Engineering, Iran University of Science & Technology (IUST), Narmak, Tehran, Iran
3) Department of Material Science, Faculty of Mechanical Engineering, K.N. Toosi University of Technology, Tehran, Iran
Abstract Effects of multiple strengthening treatments (i.e. aging either at three or four consecutive temperatures) on mechanical properties and stability of nanoscale precipitated phases in an AA2090 alloy have been evaluated in this research. Various tests such as hardness, tensile, electrical resistance, differential scanning calorimetric (DSC), and transmission electron microscopy (TEM) have been performed. The results show that the ultimate tensile strength (UTS) and the yield strength of the samples aged at four consecutive temperatures (i.e. natural aging+190°C+150°C+100°C) can be increased approximately to 660 and 610 MPa, respectively. It is also found that precipitation of T1 phase occurs during multiple aging process of the alloy and the higher amounts
of enthalpies shown in DSC charts are linked to higher volume fraction of this precipitate. Furthermore, TEM observations reveal that T1 phase has plate shape morphology and its crystal structure is in the form of hcp with lattice parameters of a=0.467 nm and c=0.878 nm.
S. Ahmadi H. Arabi A. Shokuhfar. Effects of Multiple Strengthening Treatments on Mechanical Properties and Stability of Nanoscale Precipitated Phases in an Aluminum-Copper-Lithium Alloy. J Mater Sci Technol, 2010, 26(12): 1078-1082.