【摘要】：隨著核工業(yè)技術(shù)的發(fā)展,反應(yīng)堆結(jié)構(gòu)材料將面臨越來(lái)越嚴(yán)苛的中子輻照條件。中子輻照下,材料內(nèi)部產(chǎn)生大量缺陷,進(jìn)而造成膨脹、硬化、非晶化和脆化等導(dǎo)致材料的失效。對(duì)傳統(tǒng)材料進(jìn)行結(jié)構(gòu)強(qiáng)化和性能優(yōu)化已難以滿足未來(lái)核工業(yè)對(duì)材料抗輻照性能的要求,這促進(jìn)了對(duì)新型抗輻照材料的研究。由于在許多方面表現(xiàn)出特殊的性質(zhì),近幾十年來(lái)納米晶材料一直是科學(xué)研究的熱點(diǎn)。納米晶材料最大的結(jié)構(gòu)特征是其細(xì)小的晶粒尺寸(納米級(jí))導(dǎo)致其擁有遠(yuǎn)多于普通材料的界面和晶界。以往的研究表明,晶界或界面能充當(dāng)間隙原子及空位的陷阱,因此擁有大量晶界的納米晶材料可能表現(xiàn)出優(yōu)異的抗輻照性能。鋁及合金由于擁有良好的熱、電、力學(xué)性能及抗輻照性能而廣泛應(yīng)用于核工業(yè)。目前,已能通過(guò)一些方法制備出高致密度的塊體納米晶Al,其強(qiáng)度和硬度分別可達(dá)到粗晶Al的3~16倍和2~11倍。真空熱壓是一種較為有效的納米晶材料制備技術(shù),然而目前還沒(méi)有詳細(xì)系統(tǒng)的討論真空熱壓制備納米晶Al的報(bào)道�；谏鲜銮闆r,本文以自懸浮定向流技術(shù)制備的納米Al粉末為原料,采用真空熱壓技術(shù)制得了致密的納米晶Al塊體。系統(tǒng)地討論了熱壓溫度和壓力對(duì)熱壓納米晶Al的微觀結(jié)構(gòu)和顯微硬度的影響。隨后對(duì)納米晶Al進(jìn)行了不同劑量水平的快中子(E1 Me V)輻照,討論了快中子輻照對(duì)納米晶Al微觀結(jié)構(gòu)和顯微硬度的影響。實(shí)驗(yàn)結(jié)果表明:熱壓納米晶Al塊體的顯微硬度分布在0.8~1.98 GPa范圍內(nèi),且隨熱壓溫度的升高先增大后減小,隨熱壓壓力的增大出現(xiàn)先快后慢的增長(zhǎng)。不同的熱壓溫度和熱壓壓力范圍內(nèi),不同的固結(jié)機(jī)理主導(dǎo)著納米晶Al的致密化過(guò)程。低密度塊體表現(xiàn)出明顯的壓痕尺寸效應(yīng),而高密度塊體并沒(méi)有表現(xiàn)出這種現(xiàn)象。隨不同的快中子輻照劑量,納米晶Al的平均晶粒尺寸增大了2.09%~9.09%(2.6~11 nm),顯微硬度增大了3.54%~4.37%(62.6~76.9 MPa)。隨著中子劑量的增加,納米晶Al的平均晶粒尺寸和顯微硬度的增長(zhǎng)率均表現(xiàn)出增大的趨勢(shì)。
[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.
【學(xué)位授予單位】：西南科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：TB383.1;O614.31

【共引文獻(xiàn)】

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本文編號(hào)：2387735