PREPARATION OF METAL-TIN NANOCOMPOSITE MATERIALS BY MA AND SHOCK CONSOLIDATION

在氮气保护下，对Fe-Ti和Ni-Ti混合粉末进行球磨，制备了Fe-TiN和Ni-TiN纳米晶粉末，并在38.6GPa及以上的冲击压力下，用发射药枪对球磨粉末进行了动态压制。结果表明，纳米晶Fe-63 vol.% TiN和Ni-58 vol.% TiN双相材料随晶粒尺寸的减小而增大，在临界晶粒尺寸为15 nm和10 nm时，Hv分别达到最大值14 GPa、13 GPa和12 GPa。当晶粒尺寸减小到临界值以下时，硬度略有下降。还在1000 K的温度范围内测量了高温硬度，在约500 K的低温下，晶粒尺寸低于20 nm时发生软化，在较高温度下，晶粒尺寸较大时发生软化。R.T.to软化被认为是通过扩散蠕变发生的。恒温蠕变试验表明存在一个与Coble蠕变相反的临界应力。

Fe-TiN and Ni-Tin nanocrystalline powders were prepared by ball-milling Fe-Ti and Ni-Ti powder mixtures in nitrogen gas, and the milled powders were consolidated by dynamic compaction by using a propellant gun under shock pressures of 38.6 GPa and above. It was found that the hardness of nanocrystalline Fe-63vol.%TiN and Ni-58vol.%TiN dual-phase materials increased with decreasing grain size and reached maximums of Hv=14 GPa, 13GPa and 12GPa at critical grain sizes of 15nm and 10nm, respectively. As the grain size decreased below the critical values, the hardness slightly decreased. the high temperature hardness was also measured at a temperature range from R.T.to 1000K.Softening occurred from low temperatures of about 500K with the grain sizes below 20 nm, and from higher temperatures with larger grain sizes. Softening was believed to occur via diffusional creep. A creep test at constant temperature indicated the existence of a threshould stress in contradiction to the Coble creep.