The development of microstructure of Ni 3 Al during rapid cooling and heating
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The development of microstructure of Ni3 Al during rapid cooling and heating Luhong Wang, Haozhe Liu, Kuiying Chen, and Zhuangqi Hu State Key Lab of RSA, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015, People’s Republic of China (Received 23 April 1997; accepted 27 August 1997)
The processes of rapid solidification from liquid to solid and heating from glass to crystalline for Ni3 Al are simulated using molecular dynamics method. An amorphous state can be obtained by rapid solidification as long as the cooling rate is sufficiently large, which is very difficult to get in experiment. An fcc-type crystalline is obtained by heating the amorphous with a small heating rate. Based on the pair analysis technique, the microstructures of liquid, supercooled liquid, amorphous, and crystalline states of Ni3 Al have been analyzed. Furthermore, the effects of cooling rate and heating rate on microstructures of Ni3 Al during rapid solidification and heating processes have been discussed.
I. INTRODUCTION
Molecular dynamic (MD) simulation offers a powerful means of studying microstructures of metal and alloy in a dynamic procedure, such as rapid solidification, but the success of this technique depends on the availability of suitable interatomic potentials. Simulation using empirical potential functions can provide efficient and inexpensive means for studying atomic structure and dynamics, and can also elucidate the relevant atomicscale interactions. Of these empirical potentials, the Finnis-Sinclair (F-S) potentials,1 the embedded atom method (EAM),2 the tight-binding (TB) schemes,3 and the “glue model”4 have been most widely used. In the F-S potentials, the functional form of the many-body part has been deduced using the second-moment approximation to the density of state in the tight-binding theory, i.e., assuming that the change in shape of the d-band induced by the local environment can be represented as a simple compression of the bandwidth and that there is no charge transfer between atoms.5 The success of these F-S schemes has been most remarkable in studies of surface,6,7 vacancies,7,8 interstitial,7,9,10 and grain boundaries.7,11,12 In this paper, a F-S formalism of Gao and Bacon13 is used to simulate the processes of rapid solidification from liquid to solid for Ni3 Al. A few theoretical studies for intermetallics Ni3 Al have been studied. Caro et al. simulated point defects and some low energy recoil events by using an embedded-atom potential.14 Foiles and Daw calculated surface energies and atomic relaxation of the low index faces.15 However, the nonequilibrium process of rapid quench and the evolution of microstructures during this process have not been simulated by molecular dynamics method. In this paper, a glass state of Ni3 Al, which is very difficult J. Mater. Res., Vol. 13, No. 6, Jun 1998
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to attain by rapid solidification in experiment, can be achieved by the simulation of rapid s
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