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采用自悬浮定向流-真空热压法,在不同压强下制得铝纳米晶材料,并利用X射线衍射(XRD)和正电子湮没寿命谱(PALS)分析手段对铝纳米晶的结构和微观缺陷进行表征.XRD分析表明:所制备的铝纳米晶的晶粒度为48 nm.PALS分析表明:铝纳米晶的微观缺陷主要为类空位以及空位团,而微孔洞很少;短寿命τ1,中间寿命τ2以及其对应的强度I1,I2随压强变化而呈现阶段性变化;压制压强(P)低于0.39 GPa时制得的纳米晶空位团随压强的增加而逐渐转变为类空位;0.39 GPa P 0.72 GPa时,各类缺陷发生消除;P 0.72 GPa时,各类缺陷进一步发生消除.随压强的提高,铝纳米晶的密度增加,其显微硬度也明显增高.
Aluminum nanocrystalline materials were prepared at different pressures by self-levitation flow-vacuum hot pressing. The structure and microscopic defects of aluminum nanocrystals were characterized by X-ray diffraction (XRD) and positron annihilation lifetime spectroscopy (PALS) XRD analysis showed that the grain size of the prepared aluminum nanocrystals was 48 nm.PALS analysis showed that: the microscopic defects of aluminum nanocrystals were mainly vacancies and vacancy clusters with few micropores; the short life τ1, the middle The life span τ2 and its corresponding intensity I1 and I2 showed a stepwise change with the pressure change. The nanocrystalline vacancy cluster changed to space-like vacancy with the increase of pressure when the compressive pressure (P) was lower than 0.39 GPa; 0.39 GPa P At 0.72 GPa, all kinds of defects were eliminated, and at 0.72 GPa, all kinds of defects were further eliminated. With the increase of pressure, the density of aluminum nanocrystals increased and the microhardness of the aluminum nanocrystals increased obviously.