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

在过去三年取得的主要成果如下：1.确定了Ni-Zr系非晶相的形成范围。发现超过非晶相完成的过研磨由于来自球和小瓶的杂质的积累而导致非晶相的分解。通过X射线衍射、中子衍射、EXAFS、DSC和低温比热测量，证实了具有正混合热的Cu-Ta系中非晶相的形成.在球磨过程中积累的能量的量已被确定在金属间化合物Cu 5 Zn 8，NiZr和Fe 2B通过测量在DSC光谱中的总热释放。4.我们发现在机械合金化过程中，环境温度在-150-200 ℃范围内显著影响Ni-Zr和Cu-TA合金系中非晶相的形成速率.采用机械合金化法制备了原子比为2：1的CuBa和CuY的类非晶粉末。建立了在高温氧气气氛下对类非晶态金属粉末进行热处理合成高温超导体YBCO的工艺.在NH3气氛下，采用机械合金化法制备了铁氮化物。

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.