本文選題：納米晶 + 超細(xì)晶　； 參考：《南京理工大學(xué)》2015年碩士論文

【摘要】：在金屬材料的三大失效方式中(斷裂、腐蝕和摩擦磨損),摩擦磨損直接發(fā)生與金屬的表面,而疲勞斷裂和腐蝕也是首先起始于材料的表面。因此,通過(guò)諸多化學(xué)和物理方法來(lái)改變材料表面的組織結(jié)構(gòu)或成分以滿(mǎn)足工程使用所需要的性能(表面改性)一直是材料科學(xué)與工程的重要領(lǐng)域之一。本論文利用自行設(shè)計(jì)的旋轉(zhuǎn)加速?lài)娡杼幚碓O(shè)備(RASP),對(duì)工業(yè)純鋁純銅和純銅兩種材料進(jìn)行了表面納米化處理：在材料表面通過(guò)機(jī)械變形而獲得了一定厚度的納米晶和超細(xì)晶結(jié)構(gòu)表層,并通過(guò)改變工藝參數(shù),獲得不同性能的材料,并將正交試驗(yàn)設(shè)計(jì)和和實(shí)驗(yàn)結(jié)果相結(jié)合,最終獲得最佳生產(chǎn)工藝參數(shù)。并利用金相顯微鏡、XRD、TEM等測(cè)試技術(shù)分析細(xì)晶化表面的微觀組織與顯微結(jié)構(gòu)特征,對(duì)比探討了兩種材料的細(xì)化機(jī)理。此外,運(yùn)用便攜式粗糙度儀、硬度測(cè)試儀對(duì)處理樣品表面性能進(jìn)行了測(cè)定。具體實(shí)驗(yàn)結(jié)果如下：1、工業(yè)純鋁和純銅經(jīng)過(guò)RASP處理后,表面區(qū)域均產(chǎn)生了強(qiáng)烈的塑性變形,使表面粗晶晶粒發(fā)生了明顯的細(xì)化,純銅材料表層形成了納米晶,并隨著距離表層深度的增加,塑性變形區(qū)的晶粒從納米晶逐漸增大至超細(xì)晶再增大到粗晶,純鋁表層形成了超細(xì)晶,也形成了沿表面至基體的晶粒尺寸的梯度分布。對(duì)于純銅材料,彈丸直徑越大,晶粒細(xì)化效果越好。對(duì)于純鋁,彈丸能量越高(與彈丸直徑、速度和處理時(shí)間有關(guān)),表面粗糙度和表層硬度越大,細(xì)化效果越明顯。但如果彈丸能量過(guò)高(比如處理時(shí)間為60min),超細(xì)晶粒因發(fā)生動(dòng)態(tài)再結(jié)晶而長(zhǎng)大,并使得硬度降低。2、微觀結(jié)構(gòu)觀測(cè)發(fā)現(xiàn),純鋁的晶粒細(xì)化是通過(guò)位錯(cuò)的不斷積累和反應(yīng)完成：變形首先在粗晶晶粒內(nèi)部形成高密度的位錯(cuò)纏結(jié)和位錯(cuò)墻,進(jìn)一步的位錯(cuò)積累使位錯(cuò)纏結(jié)和位錯(cuò)墻先演變成小角度亞晶界,并隨之變成大角度亞晶界和大角晶界,形成等軸狀取向隨機(jī)的超細(xì)晶組織。純鋁的位錯(cuò)細(xì)化機(jī)制是由其高的層錯(cuò)能決定的。3、對(duì)于純銅,在高速變形條件下,粗晶晶粒被高密度的孿晶分割成層片狀,隨后位錯(cuò)運(yùn)動(dòng)使層片折斷而進(jìn)一步將其細(xì)化成取向隨機(jī)的等軸納米晶。在應(yīng)變速率較低時(shí),純銅的晶粒細(xì)化機(jī)理等同于純鋁的細(xì)化機(jī)理：先由位錯(cuò)積累形成等軸狀位錯(cuò)胞,進(jìn)而形成亞微晶和納米晶。銅的這一細(xì)化特征是由其中等層錯(cuò)能所決定。應(yīng)變速率較高時(shí),變形方式主要是機(jī)械孿生；而應(yīng)變速率較低時(shí),變形方式以位錯(cuò)滑移為主。
[Abstract]:In the three failure modes of metallic materials (fracture, corrosion and friction wear), friction and wear are directly related to the surface of the metal, and fatigue fracture and corrosion are also the first to start from the surface of the material. Therefore, it is one of the important fields of material science and engineering to change the structure or composition of the material surface by a variety of chemical and physical methods to meet the performance (surface modification) required for engineering use. In this paper, the surface nanocrystals of industrial pure aluminum copper and pure copper were prepared by using the rotating accelerated shot peening equipment designed by ourselves. The nanocrystals and nanocrystals were obtained by mechanical deformation on the surface of the materials. The surface layer of ultrafine crystal structure, By changing the process parameters, the materials with different properties are obtained, and the orthogonal experimental design is combined with the experimental results to obtain the best production process parameters. The microstructure and microstructure of the fine crystalline surface were analyzed by means of metallographic microscope (TEM) and X-ray diffraction (TEM), and the refining mechanism of the two materials was compared and discussed. In addition, the surface properties of the treated samples were measured by a portable roughness tester and a hardness tester. The specific experimental results are as follows: 1. After RASP treatment of industrial pure aluminum and pure copper, the surface area of pure aluminum and pure copper has produced strong plastic deformation, resulting in obvious refinement of coarse crystal particles on the surface, and nanocrystals formed on the surface of pure copper materials. With the increase of the depth from the surface to the surface, the grain size in the plastic deformation zone gradually increases from nanocrystalline to ultrafine grain and then to coarse grain, and the superfine grain is formed on the surface of pure aluminum, and the gradient distribution of grain size is formed along the surface to the matrix. For pure copper material, the bigger the projectile diameter is, the better the grain refinement effect is. For pure aluminum, the higher the projectile energy is (related to the diameter, speed and treatment time of the projectile), the greater the surface roughness and surface hardness are, the more obvious the refining effect is. However, if the projectile energy is too high (for example, the treatment time is 60 mins, the ultrafine grain grows up because of dynamic recrystallization, and the hardness decreases by 0.2, the microstructure observation shows, The grain refinement of pure aluminum is accomplished by the continuous accumulation and reaction of dislocation: firstly, high density dislocation entanglement and dislocation wall are formed in coarse grain, and further dislocation accumulation causes dislocation entanglement and dislocation wall to evolve into small angle subgranular boundary first. And then the large angle subgranular boundary and the large angle grain boundary are formed, and the uniform axis orientation random ultrafine crystal structure is formed. The mechanism of dislocation refinement of pure aluminum is determined by its high stacking fault energy. Then the dislocation movement breaks the laminates and further refines them into randomly oriented equiaxed nanocrystals. When the strain rate is low, the grain refinement mechanism of pure copper is equivalent to that of pure aluminum: firstly, equiaxed dislocation cell is formed from dislocation accumulation, and then sub-microcrystalline and nanocrystalline are formed. This fine feature of copper is determined by the equal-stacking fault energy. When the strain rate is high, the deformation mode is mainly mechanical twinning, while when the strain rate is low, the dislocation slip is the main deformation mode.
【學(xué)位授予單位】：南京理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：TG668

【引證文獻(xiàn)】

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1 巴德瑪;馬世寧;李長(zhǎng)青;;超音速微粒轟擊38CrSi鋼表面納米化的研究[A];第六屆全國(guó)表面工程學(xué)術(shù)會(huì)議暨首屆青年表面工程學(xué)術(shù)論壇論文集[C];2006年

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本文編號(hào)：1955288