Alloying behaviour in nanocrystalline materials during mechanical alloying
Tóm tắt
The alloying behaviour in a number of systems such as Cu-Ni, Cu-Zn, Cu-Al, Ni-Al, Nb-Al has been studied to understand the mechanism as well as the kinetics of alloying during mechanical alloying (MA). The results show that nanocrystallization is a prerequisite for alloying in all the systems during MA. The mechanism of alloying appears to be a strong function of the enthalpy of formation of the phase and the energy of ordering in case of intermetallic compounds. Solid solutions (Cu-Ni), intermetallic compounds with low ordering energies (such as Ni3Al which forms in a disordered state during MA) and compounds with low enthalpy of formation (Cu-Zn, Al3Nb) form by continuous diffusive mixing. Compounds with high enthalpy of formation and high ordering energies form by a new mechanism christened as discontinuous additive mixing. When the intermetallic gets disordered, its formation mechanism changes from discontinuous additive mixing to continuous diffusive one. A rigorous mathematical model, based on iso-concentration contour migration method, has been developed to predict the kinetics of diffusive intermixing in binary systems during MA. Based on the results of Cu-Ni, Cu-Zn and Cu-Al systems, an effective temperature (T
eff) has been proposed that can simulate the observed alloying kinetics. TheT
eff for the systems studied is found to lie between 0·42–0·52T
1.
Tài liệu tham khảo
Atzmon M 1988Phys. Rev. Lett. 64 487
Balluffi R W and Rouff A L 1962Appl. Phys. Lett. 1 59
Benjamin J S 1970Metall. Trans. 1 2943
Bhattacharya A K and Arzt E 1993Scr. Metall. 28 395
Davis R M, McDermott B T and Koch C C 1988Metall. Trans. A19 2867
Dupeux M, Wan C and Willemin P 1993Acta Metall. 41 3071
Gilman P S and Benjamin J S 1983Ann. Rev. Mater. Sci. 13 279
Gleiter H 1967Acta Metall. 16 455
Hultgren R, Desai P D, Hawkins D J, Gliser M and Kelley K K 1973Selected values of thermodynamic properties of binary alloys (Metals Park, Ohio: ASM) p. 764
Koch C C 1991Materials science and technology (eds) R W Cahn, P Hassen and E Krammer (Weinheim: VCH Publishers)20 p. 193
Martin G and Gaffet E 1990J. Phys. Colloq. 51 C4–71
Murty B S and Ranganathan S 1998Int. Mater. Rev. 43 101
Murty B S, Joardar J and Pabi S K 1996Nanostructured Mater. 7 691
Noebe R D, Bowman R R and Nathal M V 1993Int. Mater. Rev. 38 193
Pabi S K 1979Phys. Status Solidi a51 281
Pabi S K and Murty B S 1996Mater. Sci. Eng. A214 146
Pabi S K, Joardar J and Murty B S 1996J. Mater. Sci. 31 3207
Pabi S K, Das D, Mahapatra T K and Manna I 1998Acta Mater. 46 3501
Schwarz R B and Koch C C 1986Appl. Phys. Lett. 49 146
Schultz R, Trudeau M and Huot J Y 1989Phys. Rev. Lett. 32 2849
Weast R C (ed.) 1995CRC handbook of chemistry and physics (Ohio: CRC Press) 72nd edn. p. F62
Williamson G K and Hall W H 1953Acta Metall. 1 22
Yavari A R 1994Mater. Sci. Eng. A179/180 20
Zbiral J, Jangg G and Korb G 1992Mater. Sci. Forum 88–90 19