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Published online by Cambridge University Press: 17 March 2011
The microstructure evolution of aluminum implanted with nickel at 5 MeV andat 100 K to a local concentration of 25 at. % is described. TransmissionElectron Microscopy (TEM) observa- tions and Rutherford BackscatteringSpectrometry (RBS) experiments are conducted to deter-mine the Ni profileand the microstructure of the implanted samples. For lower Ni concentration,it has been previously observed that Al0.75Ni0.25amorphous precipitates are formed together with a high dislocation density.When the Ni concentration reaches 25 at. %, a new crystalline multi-layeredmicrostructure is observed: the TEM observations reveal the presence ofwell-defined crystalline layers separated by sharp interfaces. To ourknowledge, it is the first time that such a structure is observed withoutfurther annealing of the implanted sample. A series of mechanisms describingthe formation of the crystalline multilayer are briefly discussed. It isargued that its formation is the result of a recrystallization frontproduced by the exothermal amorphous to crystal transformation.