【摘要】：最近幾十年,納米晶材料受到了極大的關(guān)注,越來(lái)越多的人開(kāi)始投入到納米晶材料的研究中。這種尺寸的材料不僅擁有優(yōu)異的機(jī)械性能,例如高的強(qiáng)度和高的應(yīng)變速率敏感性,而且還有很好的物理特性,如磁性。這種優(yōu)異的特性來(lái)源于它超小的晶粒尺寸,或者說(shuō)是它擁有的高的晶界體積分?jǐn)?shù),即所謂的尺寸效應(yīng)。但是這種高的晶界體積分?jǐn)?shù)同時(shí)也帶來(lái)了一些問(wèn)題,內(nèi)部不穩(wěn)定是一個(gè)很大的問(wèn)題。很多納米晶材料,無(wú)論是用于基礎(chǔ)研究,還是工程應(yīng)用,現(xiàn)在被認(rèn)為實(shí)質(zhì)上是處于非平衡狀態(tài),即使在常溫下也會(huì)自發(fā)的向粗晶轉(zhuǎn)變。這種粗晶化趨勢(shì)妨礙了其在室溫下的應(yīng)用,特別是當(dāng)它作為需要使用很長(zhǎng)時(shí)間的結(jié)構(gòu)材料。納米晶材料的粗晶化趨勢(shì)主要是由晶界的內(nèi)部活動(dòng)(例如晶界滑移、遷移、翻轉(zhuǎn))所造成的,盡管這些晶界活動(dòng)是提高塑性變形所必需的,但是,為了獲得穩(wěn)定的結(jié)構(gòu)和納米晶材料所具有的優(yōu)異特性,我們?nèi)匀恍枰浦顾Ｊ褂霉虘B(tài)不溶的元素進(jìn)行合金化是一種非常有效的方法,類(lèi)比于在乳濁液中添加表面活性劑可以穩(wěn)定表面區(qū)域,不溶的的元素會(huì)分布于晶界,從而會(huì)減小自由能,并且減緩晶粒生長(zhǎng),不溶的元素還能在晶界起著釘扎的作用。銅鉭是一個(gè)非常適合的系統(tǒng),這個(gè)系統(tǒng)的每個(gè)組元具有不同的晶體結(jié)構(gòu),在固態(tài)下具有非常小的互溶度。鉭原子的原子半徑遠(yuǎn)大于銅原子的,這會(huì)使得鉭原子分布在銅的晶界處。在本次試驗(yàn)中,使用磁控濺射的方法在玻璃基體上制備出了厚度約為6微米的納米晶銅和銅鉭合金(鉭5%)薄膜,兩種薄膜是在同樣的條件下得到的,將不溶性的納米晶銅鉭合金體系與納米晶銅進(jìn)行了對(duì)比。使用X射線(xiàn)衍射儀對(duì)納米晶銅和納米晶銅鉭合金試樣的微觀結(jié)構(gòu)進(jìn)行了分析,使用透射電子顯微鏡對(duì)其表面形貌進(jìn)行了觀察,使用納米壓痕儀對(duì)其力學(xué)性能進(jìn)行了測(cè)定,通過(guò)對(duì)比發(fā)現(xiàn)納米晶銅和納米晶銅鉭合金試樣具有相同的晶體結(jié)構(gòu)和晶粒尺寸,納米晶銅鉭合金在室溫下具有更高的硬度和抗蠕變性能,說(shuō)明鉭原子的固溶添加不會(huì)改變納米晶銅的晶體結(jié)構(gòu),可以提高納米晶銅的力學(xué)性能。將制備的納米晶銅和納米晶銅鉭合金試樣進(jìn)行一定溫度的回火處理,使用X射線(xiàn)衍射儀對(duì)納米晶銅和納米晶銅鉭合金試樣的微觀結(jié)構(gòu)進(jìn)行了分析,使用透射電子顯微鏡對(duì)其表面形貌進(jìn)行了觀察,使用納米壓痕儀對(duì)其力學(xué)性能進(jìn)行了測(cè)定,通過(guò)對(duì)比發(fā)現(xiàn)經(jīng)過(guò)回火處理后,納米晶銅鉭合金中的鉭原子向晶界偏析,納米晶銅鉭合金具有更高的硬度和抗蠕變性能,說(shuō)明晶界偏析鉭原子可以提高納米晶銅的力學(xué)性能和熱穩(wěn)定性。
[Abstract]:In recent decades, nanocrystalline materials have received great attention, and more people begin to study nanocrystalline materials. The material of this size not only has excellent mechanical properties, such as high strength and high strain rate sensitivity, but also has good physical properties, such as magnetism. This excellent property comes from its ultra-small grain size, or its high grain boundary volume fraction, known as the size effect. But this kind of high grain boundary volume fraction also brings some problems, internal instability is a big problem. Many nanocrystalline materials, whether used in basic research or engineering applications, are now considered to be essentially in a non-equilibrium state, even at room temperature will spontaneously change to coarse crystal. This trend of coarse crystallization hinders its application at room temperature, especially when it is used as a structural material for a long time. The trend of coarse crystallization of nanocrystalline materials is mainly caused by the internal activities of grain boundaries (such as grain boundary slip, migration, turnover). Although these grain boundary activities are necessary to increase plastic deformation, however, In order to obtain stable structure and excellent properties of nanocrystalline materials, we still need to stop it. Alloying with solid insoluble elements is a very effective method, analogous to the fact that adding surfactants to the emulsion stabilizes the surface area, and the insoluble elements distribute at the grain boundaries, thus reducing the free energy. And slow down the grain growth, insoluble elements can also play the role of pinning at grain boundaries. Copper tantalum is a very suitable system. Each component of the system has a different crystal structure and a very small mutual solubility in solid state. The atomic radius of tantalum atom is much larger than that of copper atom, which causes the tantalum atom to distribute at the grain boundary of copper. In this experiment, nanocrystalline copper and copper tantalum alloy (5% tantalum) thin films with thickness of about 6 microns were prepared on glass substrates by magnetron sputtering. The insoluble nanocrystalline copper-tantalum alloy system was compared with nano-crystalline copper. The microstructure of nanocrystalline copper and nanocrystalline copper-tantalum alloy samples was analyzed by X-ray diffractometer. The surface morphology of nanocrystalline copper and tantalum alloy was observed by transmission electron microscope, and the mechanical properties were measured by nano-indentation instrument. It is found that nanocrystalline copper and nanocrystalline copper tantalum alloys have the same crystal structure and grain size, and nanocrystalline copper tantalum alloys have higher hardness and creep resistance at room temperature. The results show that the addition of tantalum in solid solution can not change the crystal structure of nanocrystalline copper and can improve the mechanical properties of nanocrystalline copper. The microstructure of nanocrystalline copper and nanocrystalline copper-tantalum alloy samples was analyzed by X-ray diffraction (XRD) after tempering the samples of nanocrystalline copper and nanocrystalline copper tantalum. The surface morphology of nanocrystalline copper tantalum alloy was observed by transmission electron microscope and its mechanical properties were measured by nano-indentation instrument. It was found that after tempering, tantalum atoms in nanocrystalline copper-tantalum alloy segregated to grain boundary. Nanocrystalline copper-tantalum alloy has higher hardness and creep resistance, indicating that grain boundary segregation of tantalum atoms can improve the mechanical properties and thermal stability of nanocrystalline copper.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：O614.121;TB383.1

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