【作者】 纪秀林；

【导师】 王树奇；

【作者基本信息】 江苏大学 ， 材料学， 2005， 硕士

【摘要】 首次采用Al-Ti-B₄C和Mg-B₂O₃-TiO₂体系SHS（Self-propagating High-temperature Synthesis）制备颗粒增强镁基复合材料。根据不同技术特点,Al-Ti-B₄C体系SHS反应制得含有纯铝和陶瓷颗粒的母合金,重熔于镁液后制得原位颗粒增强镁基复合材料;Mg-B₂O₃-TiO₂体系采用直接在镁液中发生热爆反应的“热爆+浇铸”的方法制备了原位颗粒增强镁基复合材料。通过对Al-Ti-B₄C和Mg-B₂O₃-TiO₂体系SHS反应的热力学进行分析,可知Al-Ti-B₄C体系在Al含量小于60%,Mg-B₂O₃-TiO₂体系中Mg的加入量小于70%时,两种体系的SHS反应都可以自发进行,而且绝热温度随起始温度的升高而升高。Al-Ti-B₄C体系可在1200～1500℃的温度下,反应生成TiC和TiB₂颗粒。DTA和热爆试验表明,由于Al起催化剂作用,Al-Ti间反应放出的热量,使得Ti-B₄C间的反应在一个相对较低的温度条件下发生。Mg-B₂O₃-TiO₂体系的反应可在镁的熔炼温度（<800℃）下自发进行。Mg-B₂O₃-TiO₂体系内包含了三个放热反应,Mg-B₂O₃-TiO₂反应的温度介于Mg-B₂O₃和Mg-TiO₂两者的反应温度之间。对Mg-B₂O₃-TiO₂体系“热爆+浇铸”工艺的研究表明:搅拌促进颗粒均匀分布;延长混粉时间促进SHS反应;提高预热温度则缩短反应开始时间并促进SHS反应;适当的保温时间有利于形成合适的颗粒形貌。XRD和SEM对两种复合材料进行的微观分析表明,原位颗粒细小（约2μm）,TiC和MgO呈球形,TiB₂呈方形。无论拉伸强度还是硬度,这两种复合材料相对基体都有明显的提高。5%Al-Ti-B₄C体系制备的复合材料的拉伸强度、硬度分别比基体提高了约24.5%和30%。5%Mg-B₂O₃-TiO₂体系制备的复合材料的拉伸强度、硬度分别比基体提高了约26%和32%。更多还原

【Abstract】 SHS （ Self-propagating High-temperature Synthesis ） of Al-Ti-B₄C and Mg-B₂O₃-TiO₂ system are applied firstly to prepare particulate reinforced magnesium matrix composite. Based on different technical characteristics, the master alloy containing pure aluminum and ceramic particulates made from SHS reaction of Al-Ti-B₄C system is melted in molten magnesium and then the in-situ particulate reinforced magnesium matrix composite is produced. And the method of "thermal explosion + casting" that the thermal explosion of Mg-B₂O₃-TiO₂ system is happened directly in molten magnesium is used to prepare the in-situ particulate reinforced magnesium matrix composites. The thermodynamics analysis of Al-Ti-B₄C and Mg-B₂O₃-TiO₂ systems shows when Al content below 60% of Al-Ti-B₄C system and Mg addition below 70% of Mg-B₂O₃-TiO₂ system, the SHS reactions of these two kinds of systems both can be carried out by themselves and their absolutely temperatures are ascended with the starting temperatures. TiC and TiB₂ particulates can be created at 1200¹500℃ with Al-Ti-B₄C system. DTA and experiments of thermal explosion show that the Ti-B₄C reaction can be happened at a relative lower temperature by the ejective heat from Al-Ti reaction because of Al working as a catalyst in Al-Ti-B₄C system. The reaction of Mg-B₂O₃-TiO₂ system could be carried out by itself at the temperature of melting magnesium（< 800℃）. Three exothermic reactions are included in Mg-B₂O₃-TiO₂ system and Mg-B₂O₃-TiO₂ reaction temperature is between Mg-B₂O₃ and Mg-TiO₂. The research of "thermal explosion + casting" technology on Mg-B₂O₃-TiO₂ system shows that stir accelerates uniform distribution of particulates; SHS reaction is promoted for prolonging the mix time; reaction starting time is shorten and SHS reaction is boosted if preheating temperature is improved; and proper heat preservation time is of benefit to form the appropriate shape of particulates. The microcosmic analysis of XRD and SEM on these two kinds of systems shows that the in-situ particulates are fine （about 2um）, TiC and MgO are round and TiB₂ is square. Compared to magnesium matrix, not only tensile strength but also hardness of these two kinds of composites is improved obviously. The tensile strength and hardness of composites made from 5% Al-Ti-B₄C system are higher about 24.5% and 30% separately than magnesium matrix. The tensile strength and hardness of composites made from 5% Mg-B₂O₃-TiO₂ system are higher about 26% and 32% separately than magnesium matrix.更多还原