纳米晶Al的制备及其快中子辐照效应研究

发布时间：2018-12-20 08:39

【摘要】：随着核工业技术的发展,反应堆结构材料将面临越来越严苛的中子辐照条件。中子辐照下,材料内部产生大量缺陷,进而造成膨胀、硬化、非晶化和脆化等导致材料的失效。对传统材料进行结构强化和性能优化已难以满足未来核工业对材料抗辐照性能的要求,这促进了对新型抗辐照材料的研究。由于在许多方面表现出特殊的性质,近几十年来纳米晶材料一直是科学研究的热点。纳米晶材料最大的结构特征是其细小的晶粒尺寸(纳米级)导致其拥有远多于普通材料的界面和晶界。以往的研究表明,晶界或界面能充当间隙原子及空位的陷阱,因此拥有大量晶界的纳米晶材料可能表现出优异的抗辐照性能。铝及合金由于拥有良好的热、电、力学性能及抗辐照性能而广泛应用于核工业。目前,已能通过一些方法制备出高致密度的块体纳米晶Al,其强度和硬度分别可达到粗晶Al的3~16倍和2~11倍。真空热压是一种较为有效的纳米晶材料制备技术,然而目前还没有详细系统的讨论真空热压制备纳米晶Al的报道。基于上述情况,本文以自悬浮定向流技术制备的纳米Al粉末为原料,采用真空热压技术制得了致密的纳米晶Al块体。系统地讨论了热压温度和压力对热压纳米晶Al的微观结构和显微硬度的影响。随后对纳米晶Al进行了不同剂量水平的快中子(E1 Me V)辐照,讨论了快中子辐照对纳米晶Al微观结构和显微硬度的影响。实验结果表明:热压纳米晶Al块体的显微硬度分布在0.8~1.98 GPa范围内,且随热压温度的升高先增大后减小,随热压压力的增大出现先快后慢的增长。不同的热压温度和热压压力范围内,不同的固结机理主导着纳米晶Al的致密化过程。低密度块体表现出明显的压痕尺寸效应,而高密度块体并没有表现出这种现象。随不同的快中子辐照剂量,纳米晶Al的平均晶粒尺寸增大了2.09%~9.09%(2.6~11 nm),显微硬度增大了3.54%~4.37%(62.6~76.9 MPa)。随着中子剂量的增加,纳米晶Al的平均晶粒尺寸和显微硬度的增长率均表现出增大的趋势。
[Abstract]:With the development of nuclear technology, reactor structural materials will face more and more stringent neutron irradiation conditions. Under neutron irradiation, a large number of defects occur inside the material, which leads to the failure of the material, such as expansion, hardening, non-crystallization and embrittlement. The structural strengthening and performance optimization of traditional materials have been difficult to meet the requirements of the future nuclear industry for the radiation resistance of materials, which promotes the research of new type of radiation resistant materials. Nanocrystalline materials have been the focus of scientific research in recent decades because of their special properties in many aspects. The biggest structural feature of nanocrystalline materials is that their fine grain size (nanocrystalline size) leads to much more interfaces and grain boundaries than ordinary materials. Previous studies have shown that grain boundaries or interfaces can act as traps for interstitial atoms and vacancies, so nanocrystalline materials with large grain boundaries may exhibit excellent radiation resistance. Aluminum and alloys are widely used in nuclear industry due to their excellent thermal, electrical, mechanical and radiation resistance properties. At present, bulk nanocrystalline Al, with high density can be prepared by some methods. The strength and hardness of the bulk nanocrystalline Al, are 3 ~ 16 times and 2 ~ 11 times of that of coarse Al, respectively. Vacuum hot pressing is an effective preparation technology for nanocrystalline materials. However, there is no detailed report on the preparation of nanocrystalline Al by vacuum hot pressing. Based on the above situation, the dense nanocrystalline Al powders were prepared by vacuum hot pressing from nano-sized Al powders prepared by self-suspension directional flow technique. The effects of hot pressing temperature and pressure on microstructure and microhardness of hot-pressed nanocrystalline Al were systematically discussed. The effects of fast neutron irradiation (E1 Me V) on the microstructure and microhardness of nanocrystalline Al were discussed. The experimental results show that the microhardness distribution of hot-pressed nanocrystalline Al is in the range of 0.8 ~ 1.98 GPa, and increases first and then decreases with the increase of hot pressing temperature, and increases at first and then slowly with the increase of hot pressing pressure. Different consolidation mechanisms dominate the densification process of nanocrystalline Al at different hot pressing temperature and pressure range. The effect of indentation size is obvious in low density blocks, but not in high density blocks. With different doses of fast neutron irradiation, the average grain size of nanocrystalline Al increased by 9.09% (2.611 nm),) and 4.37% (62.6% 76.9 MPa). With the increase of neutron dose, the average grain size and the growth rate of microhardness of nanocrystalline Al show an increasing trend.
【学位授予单位】：西南科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1;O614.31

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