纳米碳化硅颗粒增强镁基复合材料的粉末冶金法制备及其力学性能

发布时间：2018-02-20 15:25

本文关键词： 纳米SiC 镁基复合材料组织和力学性能粉末冶金强化机制界面　出处：《吉林大学》2017年博士论文　论文类型：学位论文

【摘要】：纳米碳化硅颗粒(n-SiC_p)具有尺寸小、高模量、高硬度、高强度、低密度等优点,因此作为增强体制备金属基复合材料(MMCs)具有良好的潜力。Mg-8Al-Sn(AT81)镁合金兼顾了室温和高温的良好强度和塑性,适合作为轻质金属基体。但是,目前在纳米SiC陶瓷颗粒增强镁基复合材料的研究中还存在许多问题,比如:(1)n-SiC_p尺寸小,比表面能较大,容易团聚在一起,很难实现其在镁基体中的均匀分散;(2)n-SiC_p与基体AT81之间的界面研究较少,其界面产物对复合材料力学性能的影响缺乏系统的研究。针对上述问题,本文利用溶剂分散+机械球磨相结合的方法来实现原料的均匀分散,通过粉末冶金+热挤压制备了纳米SiC_p/AT81复合材料。研究了纳米SiC_p/AT81复合材料的微观组织及其室温力学性能;同时对纳米SiC原料进行了预氧化处理,研究了预氧化处理碳化硅颗粒(SiC_p-oxi)及SiC_p-oxi/AT81复合材料的组织和拉伸性能。研究了不同预氧化处理纳米SiC颗粒与基体AT81之间的界面以及探讨了纳米SiC_p/AT81复合材料的强化机制,对制备高性能的纳米SiC_p增强镁基复合材料具有较好的借鉴意义。本文得出的主要结论如下:1)给出了一种溶剂辅助+机械球磨相结合的方法来实现小体积分数纳米SiC增强颗粒在基体AT81中的均匀分散;研究了纳米SiC颗粒体积分数对复合材料显微组织的影响,随着纳米SiC陶瓷颗粒体积分数的增加,n-SiC_p/AT81复合材料的晶粒逐渐细化。2)研究了纳米SiC体积分数对n-SiC_p/AT81复合材料室温力学性能的影响,优化出较佳的纳米SiC陶瓷颗粒的添加量为0.50 vol.%,其室温压缩屈服强度、抗压强度和断裂应变分别为156 MPa、397 MPa和17.2%,与基体AT81相比,分别增加了81 MPa、116 MPa和5%,增幅分别是108%、41.3%和41.0%;而0.50 vol.%n-SiC_p/AT81复合材料的拉伸屈服强度、抗拉强度和延伸率分别为239 MPa、381 MPa和8.3%,比基体AT81分别提高了64 MPa、63 MPa和3.8%,增幅达到了36.6%、19.8%和84.4%;实现了在不显著牺牲塑性的前提下提升复合材料力学性能的设计思路。3)SiC_p/AT81复合材料与基体相比,在磨损过程中所产生的“犁沟”相对浅且窄,磨损表面也变得相对光滑,具有较好的耐磨性能;其中,n-SiC_p/AT81复合材料的磨损率随着陶瓷颗粒纳米SiC添加量的增加而减小;由于纳米SiC颗粒的尺寸较小、与界面接触良好等,SiC颗粒的加入降低了复合材料的腐蚀敏感性,同时降低了腐蚀速率提升了耐腐蚀性能;其中0.50 vol.%n-SiC_p/AT81复合材料在20 N载荷下的磨损率和腐蚀电流密度分别为5.05×10-3 mm3/m和4.1×10-7 A/cm2。4)通过对纳米SiC_p进行预氧化处理,0.5 vol.%n-SiC_p-oxi/AT81复合材料的屈服强度和拉伸强度均得到进一步的提升;预氧化条件为800℃/2 h时,0.5 vol.%n-SiC_p-oxi/AT81复合材料的拉伸性能较好,其屈服强度、拉伸强度和延伸率分别为255 MPa、393 MPa和5.8%;但是,当SiC_p-oxi预氧化温度进一步升高到1000℃时,0.5 vol.%n-SiC_p-oxi/AT81复合材料的屈服强度和拉伸强度均有所下降;优化出纳米SiC颗粒较佳的预氧化条件为800℃/2 h。5)未处理纳米SiC_p与AT81之间是干净的无反应界面,预氧化处理纳米SiC_p-oxi与AT81间有界面产物Mg Al2O4生成;纳米SiC_p的预氧化条件为800℃/2 h时,界面产物Mg Al2O4的厚度约为1 nm;纳米SiC颗粒的预氧化条件为1000℃/2 h时,Mg Al2O4的厚度增加到6~7 nm;界面产物Mg Al2O4的厚度直接影响n-SiC_p-oxi/AT81复合材料的力学性能;通过对纳米SiC_p/AT81复合材料的微观组织和界面的观察分析,得出复合材料的主要强化机制是热错配强化,Orowan强化、细晶强化和载荷传递强化起到了辅助作用。
[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.

【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TB333

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