本文關(guān)鍵詞：HDDR-SPS法制備納米鎂合金及其組織與力學(xué)性能研究　出處：《太原理工大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 納米晶鎂合金 HDDR處理 放電等離子燒結(jié) Hall-Petch關(guān)系

【摘要】：鎂合金是目前最輕的金屬結(jié)構(gòu)材料,具有一系列突出的優(yōu)點(diǎn)和極廣闊的發(fā)展及應(yīng)用前景。然而其較差的力學(xué)性能制約了它的廣泛應(yīng)用。晶粒細(xì)化是提高鎂合金力學(xué)性能的最佳途徑。通常情況下,金屬材料的屈服強(qiáng)度σ(或硬度)與晶粒尺寸d之間遵循Hall-Petch關(guān)系:σ=σ0+kd_(-1/2)。對(duì)于鎂合金而言,其密排六方晶體結(jié)構(gòu)對(duì)稱性低、滑移系較少,相應(yīng)的k值非常大,因而細(xì)晶強(qiáng)化的效果非常顯著。目前細(xì)化鎂合金晶粒的方法有快速凝固、劇烈塑性變形等,雖然已取得了一些成果,但是這些方法只能將鎂合金的晶粒細(xì)化到0.5~1μm左右,很難細(xì)化到100nm以下并制備出較大尺寸的試樣。本文按“商用鎂合金粉末→氫化脫氫(HDDR)處理→放電等離子(SPS)燒結(jié)→熱擠壓致密成型→組織分析及力學(xué)性能測(cè)試”的工藝路線,以商用純鎂及AZ91鎂合金切削粉末為原料,利用氫化-脫氫技術(shù)制備納米晶鎂及鎂合金粉末,通過(guò)放電等離子燒結(jié)(SPS)制備納米晶鎂及鎂合金塊體,隨后利用合適的擠壓工藝得到納米晶鎂合金棒材。利用X-射線衍射、掃描電鏡、透射電鏡等測(cè)試手段,分析了鎂合金粉末在氫化脫氫過(guò)程中的相轉(zhuǎn)變及組織演變,確定了最佳氫化脫氫工藝,并探究晶粒細(xì)化機(jī)理;研究了放電等離子燒結(jié)的納米晶鎂合金塊體材料的組織結(jié)構(gòu)及性能,并探究了鎂合金納米晶粒的組織熱穩(wěn)定性;利用萬(wàn)能試驗(yàn)機(jī),硬度測(cè)試儀等儀器設(shè)備研究熱擠壓致密成型的納米晶鎂合金棒材的組織及力學(xué)性能。結(jié)果表明,采用HDDR,SPS與熱擠壓相結(jié)合的方法,成功制備了納米鎂合金塊體材料,其平均晶粒尺寸為15nm。與鑄態(tài)與粗晶材料相比,屈服強(qiáng)度得到了很大程度的提高。并且采用這種方法制備的納米晶材料具有超高的熱穩(wěn)定性,為制備高性能納米晶鎂合金材料開辟了新途徑。
[Abstract]:Magnesium alloy is the lightest metal structure material at present. It has a series of outstanding advantages and broad development and application prospects. However, its poor mechanical properties restrict its wide application. Grain refinement is the best way to improve the mechanical properties of magnesium alloys. The relationship between yield strength 蟽 (or hardness) and grain size d follows Hall-Petch relation: 蟽 = 蟽 0 KD / 1 / 2 for magnesium alloy. Its dense hexagonal crystal structure has low symmetry, less slip system, the corresponding k value is very large, so the effect of fine grain strengthening is very remarkable. At present, the methods of refining magnesium alloy grain are rapid solidification, severe plastic deformation and so on. Although some achievements have been made, these methods can only refine the grain size of magnesium alloy to about 0.5 渭 m. It is very difficult to refine to below 100 nm and to prepare a large size sample. In this paper, according to the "commercial magnesium alloy powder" 鈫扝ydrogenated dehydrogenation (HDDR) treatment. 鈫扴park plasma sintered. 鈫扝ot extrusion compact forming. 鈫扷sing commercial pure magnesium and AZ91 magnesium alloy cutting powder as raw material, nanocrystalline magnesium and magnesium alloy powder were prepared by hydrogenation-dehydrogenation technology. Nanocrystalline magnesium alloy and magnesium alloy bulk were prepared by spark plasma sintering (SPS), then nanocrystalline magnesium alloy bars were obtained by proper extrusion process. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to prepare nanocrystalline magnesium alloy. The phase transition and microstructure evolution of magnesium alloy powder during hydrogenation and dehydrogenation were analyzed by means of transmission electron microscope. The optimum hydrogenation dehydrogenation process was determined and the grain refinement mechanism was explored. The microstructure and properties of nanocrystalline magnesium alloy bulk sintered by spark plasma sintering (SPS) were studied, and the microstructure thermal stability of magnesium alloy nanocrystalline was investigated. The microstructure and mechanical properties of nanocrystalline magnesium alloy bars formed by hot extrusion and densification were studied by means of universal testing machine and hardness tester. The results showed that HDDR was used. Nanocrystalline magnesium alloy bulk materials were successfully prepared by combining SPS with hot extrusion. The average grain size of the bulk materials was 15 nm, which was compared with the as-cast and coarse crystalline materials. The yield strength is greatly improved, and the nanocrystalline materials prepared by this method have super high thermal stability, which opens a new way for the preparation of high performance nanocrystalline magnesium alloy materials.
【學(xué)位授予單位】：太原理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TG146.22

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本文編號(hào)：1391314