The Research On Formation Regularities Of Phases Of Binary Alloy Nanometer Powders Prepared By Arc Evaporation

Nanometer particles have remarkable volume effect and surface effect, the reason why they have some abnormal properties, such as the formation regularities and structures of phases which are different from usual bulk materials.Fe-M1(M1=Ni,Ti,Mn) and Ni-M2(M2=Al,Cu) alloys were chosen as research targets for their important serviceability and use prospect. Nanometer powders were prepared by gas evaporation with arc as a heating source. Formation regularities of phases in powders, lattice parameters of alloy phases, morphologies and melting points of powders were investigated. The significant results were enumerated as follows:(1)Both the discharge current and inert gas pressure have effect on the particle size of alloy nanometer powders. Reduced discharge current and inert gas pressure make the particle size decreased and size arrange was narrower.(2)The evaporation temperature was decided by the discharge current. As-formed phases and their relative amount were changed when the arc discharge changed, but changing the argon pressure only had effect on the relative amount.(3)At the same arc discharge current and inert gas pressure, the formation regularities of phases of as-formed nanometer powders were influenced remarkably by the master alloy components. For Ni-Al system, ε-AlNi₃ and δ-AlNi phases generated easily in nanometer powders when master alloys rich in Ni were evaporated; on the other hand, when Ni component was reduced in master alloys, γ-Al₃Ni₂ phases were easily to obtain and the relative amount of this phase decreased with the decreasing of Ni. For Fe-Ti system, FCC and TiFe₂ phases were detected, when master alloys rich in Fe were evaporated; by contrast, when master alloy rich in Ti were evaporated, FCC and TiFe phases were gained. FCC phase which is a super saturated (Fe,Ti) solid solution. To Cu-Ni system, (Cu,Ni) solid solution was obtained, Only when Fe-Ni alloys were evaporated rich in Fe, (Fe,Mn) solid solutions were gained; The powders of alloys rich in Mn mostly was P-Mn. The phase formation regularities of Fe-Ni were consistent with Fe-Ni diagram.(4) Since the cooling rate was so fast that it is difficult to form low temperature alloy phases. In this research work, the low temperature phases of β-Al₃Ni₅and Al₃Ni in Ni-Al system, a-Ti in Fe-Ti system, α₁ and α₂ in Ni-Cu system and a-Mn in Fe-Mn system were not detected. The formation of the low temperature phase FeNi₃ in Fe-Ni system may be due to the dynamic factor in the procedure of formation.