Formation and decomposition Processes of Non-Equilibrium phase by Mechanical alloying

近三年取得的主要成果如下：确定了Ni-Zr体系中非晶相的形成范围。发现在非晶相完成之后的复磨会导致非晶相的分解，这是由于球和小瓶中杂质的积累。用x射线衍射、中子衍射、EXAFS、DSC和低温比热测量证实了Cu-Ta体系中非晶相的形成，其混合热为正。通过测量DSC光谱中的总放热，确定了金属间化合物Cu5Zn8、NiZr和Fe2B在球磨过程中积累的能量。结果表明：在-150 ~ 200℃范围内的环境温度对Ni-Zr和CU-TA合金体系在机械合金化过程中非晶相的形成速率有显著影响。将CuBa和CuY以2:1的原子比进行机械合金化，合成了非晶状粉末。通过在氧流气氛中对非晶状金属粉末进行高温热处理，建立了合成高tc超导体YBCO的技术。在nh3气氛中对纯铁粉进行机械合金化，合成了氮化铁。

Major Results obtained in the last three years are listed below :1. The formation range of an amorphous phase in Ni-Zr system has been determined. The overmilling beyond the completion of an amorphous phase is found to cause the decomposition of an amorphous phase due to the accumulation of impurities from balls and vial.2. The formation of an amorphous phase has been confirmed by X-ray diffraction, neutron diffraction, EXAFS, DSC and low-temperature specific heat measurements in the Cu-Ta system characterized by a positive heat of mixing.3. The amount of energy accumulated during ball milling has been determined in the intermetallic compounds Cu5Zn8, NiZr and Fe2B by measuring the total heat release in the DSC spectra.4. We found that the ambient temperature in the range -150-200ﾟC has substantially affected the formation rate of an amorphous phase in Ni-Zr and CU-TA alloy system during mechanical alloying.5. Amorphous-like powders were synthesized by mechanical alloying of a mixture of CuBa and CuY in 2 : 1 atomic ratio. The technique in synthesizing high-Tc superconductor YBCO has been established by heat-treating the amorphous-like metallic powders at elevated temperature in oxygen-flow atmosphere.6. The iron nitrides were synthesized by mechanically alloying pure iron powders in NH3-atmosphere.