J. Mater. Sci. Technol. ›› 2010, Vol. 26 ›› Issue (12): 1078-1082.

• Research Articles • 上一篇    下一篇

Effects of Multiple Strengthening Treatments on Mechanical Properties and Stability of Nanoscale Precipitated Phases in an Aluminum- Copper- Lithium Alloy

shahram ahmadi   

  1. Tarbiat Modares University
  • 收稿日期:2009-05-21 修回日期:2010-02-02 出版日期:2010-12-31 发布日期:2010-12-21
  • 通讯作者: shahram ahmadi

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. 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
  • Received:2009-05-21 Revised:2010-02-02 Online:2010-12-31 Published:2010-12-21
  • Contact: shahram ahmadi

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摘要： Abstract Effects of multiple strengthening treatments (aging in three and four subsequent temperatures) on mechanical properties and stability of nanoscale precipitated phases in an AA2090 alloy was evaluated by hardness, tensile, electrical resistance, differential scanning calorimetric (DSC), and transmission electron microscopy (TEM) tests. Results show that while hardness, UTS, and yield strength of the sample aged at four subsequent temperatures (i.e. natural aging, 190oC, 150oC, and 100oC) are more than those of the other specimens, its electrical resistance is in the lowest amount. It is also proof that T1 phase precipitation occurs during multiple aging processes in the structure of the alloy and higher amount of enthalpy (in DSC charts) are linked to higher volume fraction of phases or precipitates. Furthermore, TEM observations have revealed that T1 phase has plate shape morphology and its crystal structure is in the form of hexagonal close- packed. In addition, the lattice parameters were found to be; a=0.4672 nm and c= 0.8785 nm.

关键词: Keywords: Multiple strengthening (aging), thermo mechanical treatment (TMT), differential scanning calorimetric (DSC), selected area diffraction pattern (SADF), interplanar spacing (d)

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.

Key words: Multiple strengthening, Thermo mechanical treatment (TMT), Selected area electron diffraction (SAED) pattern, Inter planar spacing (d)