Preparation And Response To Fast Neutron Irradiation Of Nanocrystalline Al

With the rapid development of the nuclear technology, the materials in the nuclear reactors will face harsher neutron irradiation conditions. Under neutron irradiation, numerous defects generate in material, which subsequently causes swelling, hardening, amorphization and embrittlement, eventually leading to material failure. Incremental improvements to conventional materials cannot meet increased demands of future technologies. New concepts in materials design are needed to manufacture materials that resist damage at extreme irradiation conditions. It has long been known that surfaces, grain boundaries and interphase boundaries are sinks for radiation-induced point defects and traps for helium. Therefore, nanocrystalline(nc) materials, which has small grain sizes and resultant numerous boundaries, are deemed to have huge potentials as new generation radiation-resistant materials.Al and its alloys had widely used in nuclear industry due to their excellent thermal, electrical, mechanical performance and radiation tolerance. Nc Al has been prepared by several methods and they show much higher strength and hardness than conventional aluminum(3-16 and 2-11 times, respectively). Hot pressing is an effective method to consolidate nanopowders into bulk nc materials, while there is no systematic reports on preparation of nc Al by hot pressing.Based on the situations above, using Al nanopwders as raw materials, we have prepared nc Al by hot pressing technique and then analyzed detailedly the effect of the temperature and pressure of hot pressing process on microstructure and mechanical properties of nc Al. Furthermore, through irradiating nc Al with fast neutrons(E>1 Me V), we studied the influence of fast neutron irradiation on microstructure and mechanical properties of nc Al.The results indicates that The microhardness of nc Al, which ranges from 0.8 to 1.98 GPa, increases firstly and then decreases with the increase of the hot pressing temperature, and shows fast and then slow increase with raising the hot pressing pressure. Different from the high-density nc Al bulks, the bulks with low density obviously show an indentation size effect. The different mechanisms dominate the densification process of nc Al at different hot-pressing temperatures and pressures. After fast neutron irradiation, due to existence of defects induced by irradiation, which indicated by change of electrical resistance, the microhardness of nc Al increase 2.09%- 9.09%(62.6- 76.9 MPa), while the average grain size increase 3.54%- 4.37%(2.6- 11 nm). The increasing rate of the average grain size and microhardness becomes larger with the increase of fast neutron dose.