Synthesis of crystallite-dispersed nano-composites by ion implantation into amorphous alloys

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The applicability of ion-implantation induced local crystallization of amorphous alloys to the synthesis of crystal/amorphous nano-composites was studied. Helium ions were used as implant species since they are chemically most inactive. For target materials, Fe-B and Fe-Si-B alloys were used as representatives of metal- metalloid type amorphous alloys, whereas Fe-Zr alloy was selected as typical metal-metal type amorphous alloy. After installing a unit for precision control of implantation temperature, implantations were conducted on Fe-B alloy samples. However, systematic preparation of implanted samples was not possible due to the malfunction of the ion implanter. Thus the following were concluded from the results only on Fe-B alloys: 1) the amount of induced crystalline phase increases with increasing dose and saturates at high doses; the dose dependence becomes moderated by lowering implantation temperature so that the amount becomes well controllable, 2) no significant change is observed in local structure and in thermal stability after implantation if doses are below the critical dose for crystallization, 3) when the amount of induced crystalline phase is small, crystalline fine particles are magnetically isolated from the residual amorphous phase(s), 4) crystalline fine particles seems to grow by integrating neighboring parlicles, which are unfavorable for the present purpose because amount and size of crystalline particles cannot be controlled independently. The comparison with the results for Fe-Si-B and Fe-Zr will be reported as soon as possible.