本文關(guān)鍵詞： 納米SiC 鎂基復(fù)合材料 組織和力學(xué)性能 粉末冶金 強化機制 界面　出處：《吉林大學(xué)》2017年博士論文　論文類型：學(xué)位論文

【摘要】：納米碳化硅顆粒(n-SiC_p)具有尺寸小、高模量、高硬度、高強度、低密度等優(yōu)點,因此作為增強體制備金屬基復(fù)合材料(MMCs)具有良好的潛力。Mg-8Al-Sn(AT81)鎂合金兼顧了室溫和高溫的良好強度和塑性,適合作為輕質(zhì)金屬基體。但是,目前在納米SiC陶瓷顆粒增強鎂基復(fù)合材料的研究中還存在許多問題,比如:(1)n-SiC_p尺寸小,比表面能較大,容易團聚在一起,很難實現(xiàn)其在鎂基體中的均勻分散;(2)n-SiC_p與基體AT81之間的界面研究較少,其界面產(chǎn)物對復(fù)合材料力學(xué)性能的影響缺乏系統(tǒng)的研究。針對上述問題,本文利用溶劑分散+機械球磨相結(jié)合的方法來實現(xiàn)原料的均勻分散,通過粉末冶金+熱擠壓制備了納米SiC_p/AT81復(fù)合材料。研究了納米SiC_p/AT81復(fù)合材料的微觀組織及其室溫力學(xué)性能;同時對納米SiC原料進行了預(yù)氧化處理,研究了預(yù)氧化處理碳化硅顆粒(SiC_p-oxi)及SiC_p-oxi/AT81復(fù)合材料的組織和拉伸性能。研究了不同預(yù)氧化處理納米SiC顆粒與基體AT81之間的界面以及探討了納米SiC_p/AT81復(fù)合材料的強化機制,對制備高性能的納米SiC_p增強鎂基復(fù)合材料具有較好的借鑒意義。本文得出的主要結(jié)論如下:1)給出了一種溶劑輔助+機械球磨相結(jié)合的方法來實現(xiàn)小體積分數(shù)納米SiC增強顆粒在基體AT81中的均勻分散;研究了納米SiC顆粒體積分數(shù)對復(fù)合材料顯微組織的影響,隨著納米SiC陶瓷顆粒體積分數(shù)的增加,n-SiC_p/AT81復(fù)合材料的晶粒逐漸細化。2)研究了納米SiC體積分數(shù)對n-SiC_p/AT81復(fù)合材料室溫力學(xué)性能的影響,優(yōu)化出較佳的納米SiC陶瓷顆粒的添加量為0.50 vol.%,其室溫壓縮屈服強度、抗壓強度和斷裂應(yīng)變分別為156 MPa、397 MPa和17.2%,與基體AT81相比,分別增加了81 MPa、116 MPa和5%,增幅分別是108%、41.3%和41.0%;而0.50 vol.%n-SiC_p/AT81復(fù)合材料的拉伸屈服強度、抗拉強度和延伸率分別為239 MPa、381 MPa和8.3%,比基體AT81分別提高了64 MPa、63 MPa和3.8%,增幅達到了36.6%、19.8%和84.4%;實現(xiàn)了在不顯著犧牲塑性的前提下提升復(fù)合材料力學(xué)性能的設(shè)計思路。3)SiC_p/AT81復(fù)合材料與基體相比,在磨損過程中所產(chǎn)生的“犁溝”相對淺且窄,磨損表面也變得相對光滑,具有較好的耐磨性能;其中,n-SiC_p/AT81復(fù)合材料的磨損率隨著陶瓷顆粒納米SiC添加量的增加而減小;由于納米SiC顆粒的尺寸較小、與界面接觸良好等,SiC顆粒的加入降低了復(fù)合材料的腐蝕敏感性,同時降低了腐蝕速率提升了耐腐蝕性能;其中0.50 vol.%n-SiC_p/AT81復(fù)合材料在20 N載荷下的磨損率和腐蝕電流密度分別為5.05×10-3 mm3/m和4.1×10-7 A/cm2。4)通過對納米SiC_p進行預(yù)氧化處理,0.5 vol.%n-SiC_p-oxi/AT81復(fù)合材料的屈服強度和拉伸強度均得到進一步的提升;預(yù)氧化條件為800℃/2 h時,0.5 vol.%n-SiC_p-oxi/AT81復(fù)合材料的拉伸性能較好,其屈服強度、拉伸強度和延伸率分別為255 MPa、393 MPa和5.8%;但是,當SiC_p-oxi預(yù)氧化溫度進一步升高到1000℃時,0.5 vol.%n-SiC_p-oxi/AT81復(fù)合材料的屈服強度和拉伸強度均有所下降;優(yōu)化出納米SiC顆粒較佳的預(yù)氧化條件為800℃/2 h。5)未處理納米SiC_p與AT81之間是干凈的無反應(yīng)界面,預(yù)氧化處理納米SiC_p-oxi與AT81間有界面產(chǎn)物Mg Al2O4生成;納米SiC_p的預(yù)氧化條件為800℃/2 h時,界面產(chǎn)物Mg Al2O4的厚度約為1 nm;納米SiC顆粒的預(yù)氧化條件為1000℃/2 h時,Mg Al2O4的厚度增加到6~7 nm;界面產(chǎn)物Mg Al2O4的厚度直接影響n-SiC_p-oxi/AT81復(fù)合材料的力學(xué)性能;通過對納米SiC_p/AT81復(fù)合材料的微觀組織和界面的觀察分析,得出復(fù)合材料的主要強化機制是熱錯配強化,Orowan強化、細晶強化和載荷傳遞強化起到了輔助作用。
[Abstract]:Nano SiC particles (n-SiC_p) with small size, high modulus, high hardness, high strength, low density etc., so as to enhance the preparation of metal matrix composites (MMCs) has a good potential of.Mg-8Al-Sn (AT81) magnesium alloy with good strong room temperature and high temperature and plastic, suitable for light metal matrix however, at present in the nano SiC ceramic particles reinforced many problems still exist on the magnesium based composite materials such as: (1) n-SiC_p small size, large surface energy, easy to get together, it is difficult to achieve its in the magnesium matrix uniformly dispersed; (2) the interface between n-SiC_p and AT81 matrix less, the system of the product interface on the mechanical properties of the composites are lacking. In view of the above problems, uniform dispersion method using solvent dispersion + mechanical milling to achieve a combination of raw materials, prepared by powder metallurgy + hot extrusion The nano SiC_p/AT81 composite was studied. The microstructure and mechanical properties of nano SiC_p/AT81 composite materials; at the same time on the nano SiC materials are pre oxidation treatment of pre oxidation treatment of silicon carbide particles (SiC_p-oxi) microstructure and tensile properties of SiC_p-oxi/AT81 and composite materials. Effects of different pre oxidation treatment between SiC particles and AT81 matrix the interface and discusses the strengthening mechanism of nano SiC_p/AT81 composite materials, the preparation of high performance nano SiC_p reinforced magnesium matrix composites have good reference. The main conclusions of this paper are as follows: 1) dispersion gives a method of solvent assisted mechanical milling + combination to achieve small volume fraction of nano SiC reinforced the particles in the AT81 matrix; effects of the volume fraction of nano SiC particles on the microstructure of the composites with nano SiC ceramic particles. The increase of the volume fraction, grain size of n-SiC_p/AT81 composite materials gradually refine effect of nano SiC.2) volume fraction on the mechanical properties of n-SiC_p/AT81 composite, optimize the addition of nano SiC ceramic particles better is 0.50 vol.%, the compressive yield strength, compressive strength and fracture strain were 156 MPa, 397 MPa and 17.2%, compared with the AT81 matrix, which increased by 81 MPa, 116 MPa and 5%, an increase of respectively 108%, 41.3% and 41%; and 0.50 vol.%n-SiC_p/AT81 composite tensile yield strength, tensile strength and elongation are 239 MPa, 381 MPa and 8.3%, than AT81 were increased by 64 MPa, 63 MPa and 3.8%, an increase of 36.6%, 19.8% and 84.4%; to achieve without significantly sacrificing plastic design ideas to improve the mechanical properties of the composite material.3) SiC_p/AT81 composites and matrix than in the wear process of the The furrow "relatively shallow and narrow, the wear surface becomes relatively smooth, has good abrasion resistance; wherein, the wear rate of n-SiC_p/AT81 composites decreases with the increasing amount of ceramic nano SiC particles; due to the small size of SiC nanoparticles, with good interface contact, the addition of SiC particles reduces the corrosion the sensitivity of the composite, while reducing the corrosion rate to enhance the corrosion resistance of the composite materials; 0.50 vol.%n-SiC_p/AT81 under the load of 20 N the wear rate and the corrosion current density was 5.05 mm3/m * 10-3 and 4.1 * 10-7 A/cm2.4) based on the nano SiC_p pre oxidation treatment, 0.5 vol.%n-SiC_p-oxi/AT81 composite material yield strength and tensile strength have been further improved; pre oxidation condition was 800 /2 DEG h, the tensile properties of 0.5 vol.%n-SiC_p-oxi/AT81 composites is better, its yield strength, The tensile strength and elongation were 255 MPa, 393 MPa and 5.8% SiC_p-oxi; however, when pre oxidation temperature is further increased to 1000 DEG C, 0.5 vol.%n-SiC_p-oxi/AT81 composite material yield strength and tensile strength were decreased; optimization of pre oxidation of SiC nano particles is preferably 800 DEG C /2 H.5) treated without reaction the interface between Nano SiC_p and AT81 are clean, pre oxidation treatment of nano SiC_p-oxi and AT81 interface between product Mg Al2O4 formation; pre oxidation conditions of nano SiC_p 800 C /2 h, Mg Al2O4 interface product is about 1 nm in thickness; pre oxidation of SiC nano particles is 1000 DEG C /2 h, Mg the thickness of Al2O4 increased to 6~7 nm; Mg Al2O4 product interface thickness directly affects the mechanical properties of n-SiC_p-oxi/AT81 composite materials; through the observation on Microstructure of nano SiC_p/AT81 composite materials and interface analysis, the composite material The main strengthening mechanisms are thermal mismatch strengthening, Orowan strengthening, fine grain strengthening and load transfer enhancement.

【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：TB333

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