Development of amorphous Al65Cu35−xTix alloys by mechanical alloying
Introduction
Development of high-specific strength structural material is always of great importance to the transportation and aviation industry. It is predicted that the strength of light weight aluminium alloys could be significantly enhanced from about 500–600 MPa in age hardened condition to 1200–1550 MPa level in rapidly quenched glassy/amorphous or nanocrystal dispersed glassy/amorphous matrix aluminium based alloys [1]. In the recent times, mechanical alloying has emerged as a convenient solid state synthesis alternative to melt spinning and similar rapid quenching techniques to develop the metallic glasses [2], [3], [4]. Furthermore, carefully designed milling routine and/or subsequent heat treatment may enable dispersion of nanocrystalline intermetallic phases in the mechanically alloyed amorphous/glassy matrix precursor [5], [6]. Recently, we have demonstrated for the first time that mechanical alloying of the Al65Cu35−xTix ternary system within a close composition range yields completely or partially amorphous alloy [7]. However, the phase identity and evolution during milling and/or subsequent annealing in this system have not been determined. In the present paper, we shall report the phase evolution sequence during mechanical alloying and subsequent isothermal annealing (at 773 K) of the selected alloys in the Al65Cu35−xTix ternary system. In addition, we shall also identify an appropriate composition that can yield a completely amorphous microstructure by mechanical alloying.
Section snippets
Experimental
Blends of elemental (>99.5 wt.% purity) Al, Cu, and Ti powders (∼50–100 μm particle size) having the nominal compositions (in at.%) of Al65Cu35−xTix (x=5, 10, 15, 20, 25 and 30 at.%) were ball milled in a Fritsch Pulverisette 5 planetary ball mill at 300 rpm and ball to powder weight ratio of 10:1 using WC vial and balls (10 mm diameter) in stages with up to a cumulative milling time of 40 h. The initial composition of the powder blend varied in the range x=5–30 (at.% Ti) to determine the solid
Mechanical alloying
Fig. 1 reveals the XRD patterns obtained from the Al65Cu20Ti15 samples subjected to mechanical alloying for different lengths of milling time. It is apparent that the intensities of the peaks due to the elemental constituents (Al, Cu and Ti) are considerably reduced by 6 h of milling with simultaneous evolution of additional peaks which may be indexed as the disordered Cu9Al4 phase having a bcc Bravais lattice [9]. In addition to decreasing the intensity, continued ball milling seems to induce
Conclusion
Mechanical alloying of Al65Cu35−xTix (10<Ti<25 at.%) by planetary ball milling up to 30 h leads to the formation of a single phase amorphous or nanocrystalline product. Controlled milling up to (or arresting the milling at) the appropriate stage may develop an in situ composite microstructure comprising amorphous (to a varying degree) and nanocrystalline metallic/intermetallic phases. Ti plays a crucial role in solid state amorphization of Al65Cu20Ti15. Subsequent isothermal annealing of the
Acknowledgements
Useful discussions with Prof. Dr. H.-J. Fecht and Dr. J. Eckert about the results presented in this work are gratefully acknowledged. Partial financial support from the Department of Science and Technology, New Delhi (grant no.: III.4 (23) 92-ET and SP/S2/K-17/98 dt. 29.1.99) is thankfully acknowledged.
References (13)
Mater Sci Eng A
(1994)- et al.
J Less Common Met
(1988) - et al.
Scripta Metall Mater
(1997) - et al.
Appl Phys Lett
(1983) - et al.
Appl Phys Lett
(1997) - Koch, C. C. (1991). In R. W. Cahn, P. Hassen & E. J. Kramer (Eds.). Processing of Metals and Alloys (Vol. 15, p. 193)....
Cited by (31)
Synthesis mechanisms and effects of BaTiO<inf>3</inf> doping on the optical properties of Bi<inf>0.5</inf>Na<inf>0.5</inf>TiO<inf>3</inf> lead-free ceramics
2022, Journal of Solid State ChemistryCitation Excerpt :Earlier authors have proved that mechanical alloying gives single-phase amorphous or nanocrystalline materials [46,58–64]. They demonstrated that adequate heat treatment of mechanically alloyed material allows in situ dispersion of nanocrystalline powders [65,66]. The high temperature and pressure can lead to partial crystallization or grain coarsening of the material.
Study on crystallization kinetics of Al<inf>65</inf>Cu<inf>20</inf>Ti <inf>15</inf> amorphous alloy
2011, Journal of Non-Crystalline SolidsCitation Excerpt :It has been suggested that strength of the amorphous materials can be further enhanced, and limited ductility can be introduced through the dispersion of nanometric phases [5,6]. Besides rare-earth addition, a number of Al65CuxTm35 − x or Al50TmxSi50 − x type alloys were developed by mechanical alloying that also possess amorphous or nano-intermetallic dispersed amorphous microstructure [7–10]. Roy et al. [11] have been achieved a bulk compressive strength of 1490 MPa as well as impressive hardness of 7.9 GPa by high pressure sintering of mechanically alloyed amorphous Al65Cu20Ti15 powder.
Structure and mechanical properties of Al<inf>65</inf>Cu<inf>20</inf>Ti<inf>15</inf>-based amorphous/nanocrystalline alloys prepared by high-pressure sintering
2008, Materials Science and Engineering: AMicrostructure and mechanical properties of mechanically alloyed and spark plasma sintered amorphous-nanocrystalline Al<inf>65</inf>Cu<inf>20</inf>Ti<inf>15</inf> intermetallic matrix composite reinforced with TiO<inf>2</inf> nanoparticles
2007, IntermetallicsCitation Excerpt :Development of materials with high specific strength is always of interest in structural applications for automobiles and aerospace sectors. Recently, the Al-based bulk amorphous alloys have received considerable research attention [1–3]. Significantly high tensile or compressive strength in the range of 1000–1550 MPa has been achieved in the Al alloys with completely or partially amorphous matrix [4–7], while the age-hardenable Al alloys can attain a maximum strength level of 500–600 MPa in suitable heat treated condition [8].
Phase evolution in Al-Ni-(Ti, Nb, Zr) powder blends by mechanical alloying
2007, Materials Science and Engineering: A