本文選題：表面納米化 + 表面合金化�。� 參考：《太原理工大學》2016年碩士論文

【摘要】：近年來,具有優(yōu)異的力學性能和獨特的微觀結(jié)構(gòu)的納米材料已經(jīng)成為人們的研究熱點。材料表面納米化是在材料表面制備出具有一定厚度的納米結(jié)構(gòu)表層,通過改變其組織結(jié)構(gòu)以及應(yīng)力狀態(tài),使材料的整體力學性能得到改善的方法。表面機械合金化(SMA)技術(shù)來源于表面納米化技術(shù),是表面強烈塑性變形(SPD)的另一分支領(lǐng)域,是在進行表面機械研磨的同時引入不同于基體的成分,形成具有納米梯度結(jié)構(gòu)的復合表面,以滿足材料表面多樣性的要求。本文通過實驗對比FCC結(jié)構(gòu)金屬(Cu)和HCP結(jié)構(gòu)金屬(Mg)機械研磨過程中參數(shù)配比問題,并探討其表面納米化和合金化過程的區(qū)別,以及期望制備出表面性能更好的納米結(jié)構(gòu)層,研究了合金化過程中原子擴散的問題。(1)由于純銅和純鎂晶體結(jié)構(gòu)不同,并且其層錯能也不同,導致塑性變形過程機理也不相同,純銅變形機理包括(a)位錯纏結(jié)和位錯墻在原始粗晶以及細化胞中演變、(b)形成小角度亞晶界、(c)小角度亞晶界轉(zhuǎn)化為大角度亞晶界及納米晶三個步驟,位錯機制對塑性變形過程起主要貢獻;純鎂變形機理包括(a)應(yīng)力應(yīng)變誘發(fā)孿晶結(jié)構(gòu)形成、(b)孿晶間的交互作用發(fā)展為位錯的纏結(jié)、(c)動態(tài)再結(jié)晶過程三個步驟,塑性變形過程初期以孿生交互機制為主,隨著應(yīng)力應(yīng)變持續(xù)作用,位錯機制對變形過程起主要作用。(2)在相同納米化體系中,彈丸尺寸增大對納米化效果起促進作用,塑性變形層厚度增加,納米晶尺寸減小。特別是純鎂基體,8 mm的彈丸作用下,表層擇優(yōu)取向面發(fā)生變化,由原先的(101)晶面擇優(yōu)變?yōu)?002)晶面和(101)晶面共同擇優(yōu)。(3)在相同納米化體系中,smat時間增長對納米化效果(深度及晶粒大小)起促進作用,塑性變形層厚度明增加,納米晶尺寸減小,晶格畸變嚴重。(4)將表面納米化法和表面機械合金化法結(jié)合,在純cu、純mg表面得到均勻、連續(xù)的ni涂層和cu-ni、mg-ni復合涂層。這一種新的方法對原位形成表面復合涂層提供了實驗指導。(5)經(jīng)過表面納米化預處理30min的cu板、mg板合金化效率明顯高于未處理過的cu板、mg板,合金化4h后,預處理的樣品ni涂層厚度可以分別達到40μm和60μm,分別是未預處理樣品的8和6倍。涂層的厚度、均勻性和連續(xù)性隨合金化時間延長而提高。(6)經(jīng)過表面合金化后樣品表面硬度得到很大的提高,純銅樣品表面硬度從98hv提高到280hv,提高2.8倍;純鎂樣品表面硬度從45hv提高到340hv,提高7.5倍。(7)涂層的形成主要經(jīng)歷了三個階段:粉體與基體機械結(jié)合、形成冷焊層和互擴散(擴散)過程。并且經(jīng)過預處理后,基體表層發(fā)生嚴重的塑性變形,導致表層呈現(xiàn)凹凸不平的形貌,表面積增大,表面硬度提高,促進合金涂層形成。(8)在塑性變形過程中,原始粗晶由于應(yīng)力應(yīng)變作用發(fā)生嚴重扭折,細化,晶粒之間存在大量晶界特別是三岔晶界,晶粒內(nèi)部存在大量位錯線等缺陷。(9)在塑性變形過程中,由于晶界、位錯等缺陷增多,局部溫度升高,Ni以原子的形式在純銅、純鎂基體中擴散。
[Abstract]:In recent years, nanomaterials with excellent mechanical properties and unique microstructures have become a hot spot of research. The surface nanocrystallization of materials is a method to improve the overall mechanical properties of the material by changing the structure and stress state of the surface of the material with a certain thickness. Surface mechanical alloying (SMA) technology is derived from surface nanoscale technology. It is another branch of surface strong plastic deformation (SPD). It is introduced into a composite surface with a nano gradient structure to meet the requirements of the material surface diversity. In this paper, a comparison of FCC is made in this paper. The problem of parameter ratio in mechanical lapping of structural metal (Cu) and HCP structure metal (Mg), and the difference between the surface nanoscale and alloying process, as well as the preparation of the nano structure layer with better surface properties, the problem of atomic diffusion in the process of alloying. (1) the structure of pure copper and pure magnesium is different and its layer is wrong. The mechanism of plastic deformation process is different, and the deformation mechanism of the plastic deformation is different. The deformation mechanism of pure copper includes (a) dislocation entanglement and dislocation wall in the original coarse grain and refined cell. (b) formation of small angle subgrain boundary, (c) small angle subgrain boundary into large angle subgrain boundary and nanocrystalline step, dislocation mechanism plays the main contribution to the plastic deformation process. The mechanism of pure magnesium deformation includes (a) the formation of stress strain induced twin structure, and the interaction between (b) twins develops into dislocation entanglement, (c) the dynamic recrystallization process of (c), the early stage of the plastic deformation process is twin interaction mechanism, with the continuous action of stress and strain, the dislocation mechanism plays a major role in the deformation process. (2) in the same nanometer In the system, the size of the projectile increases to the nanocrystalline effect, the thickness of the plastic deformation layer increases and the size of nanocrystalline decreases. Especially the pure magnesium matrix, under the action of 8 mm projectiles, the preferential orientation surface of the surface changes from the original (101) crystal surface to (002) crystal surface and (101) crystal surface together. (3) in the same nanoscale system, s The time growth of mat promotes the nanocrystalline effect (depth and grain size), the thickness of the plastic deformation layer increases, the size of the nanocrystalline decreases, and the lattice distortion is serious. (4) the surface nanocrystallization and the surface mechanical alloying method are combined, the pure Cu, the pure Mg surface is uniform, the continuous Ni coating and the Cu-Ni, Mg-Ni composite coating. The method provides experimental guidance for the in-situ surface composite coating. (5) after the surface nanocrystalline pretreatment of 30min Cu plate, the alloying efficiency of the Mg plate is obviously higher than that of the untreated Cu plate. After the Mg plate and the alloying 4h, the thickness of the pre treated sample Ni coating can reach 40 Mu and 60 u respectively, respectively, 8 and 6 times of the untreated samples. The thickness of the coating, respectively. The uniformity and continuity increased with the alloying time. (6) the surface hardness of the sample was greatly improved after the surface alloying. The surface hardness of pure copper samples increased from 98hv to 280hv, and increased by 2.8 times. The surface hardness of pure magnesium samples increased from 45hv to 340hv, up to 7.5 times. (7) the formation of the coating mainly experienced three stages: powder and base The cold welding layer and diffusion (diffusion) process are formed by body mechanical combination. And after pretreatment, the surface of the matrix has serious plastic deformation, which leads to uneven surface appearance, the surface area increases, the surface hardness is increased, and the alloy coating is promoted. (8) during the plastic deformation process, the original coarse grain is serious due to the stress and strain effect. There are a large number of grain boundaries, especially the three fork grain boundaries, and there are a large number of dislocation lines in the grain. (9) in the process of plastic deformation, due to the increase of grain boundary, dislocation and other defects, the local temperature increases, and Ni diffusion in pure copper and pure magnesium matrix in the form of atoms.

【學位授予單位】：太原理工大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：TG580.68

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