【作者】 傅爱琼；

【导师】 严有为；

【作者基本信息】 华中科技大学 ， 材料加工工程， 2005， 硕士

【摘要】 与传统的Al-Ti-B 中间合金相比,Al-Ti-C 中间合金细化剂较少存在诸如TiB2粒子尺寸较大,且易被铝液中微量的Zr、Cr、Mn 等元素“毒化”而导致晶粒细化效果衰退等问题。因此,Al-Ti-C 中间合金被认为是最有发展前途的铝及铝合金的晶粒细化剂。但是,由于C 与液态Al 不润湿等原因,采用传统的熔炼方法一般难以稳定制备这种细化剂。因此,研究开发该细化剂的制备新技术一直是人们追求的目标。在此基础上,本文提出了一种制备该细化剂的新方法-自蔓延高温合成(SHS)技术。基于溶液热力学理论,本文首先对Al-Ti-C 三元体系的反应热力学进行了理论分析和计算。结果表明,在Al 液的高温作用下,浸入其中的Al-Ti-C 预制块可以发生SHS 反应,合成晶粒细化剂中所需的Al3Ti 和TiC 相,从而可望开发制备Al-Ti-C 晶粒细化剂的铝液中的SHS 工艺。采用直接SHS 工艺和在高温铝液中的SHS 工艺,分别制备出了Al-Ti-C 中间合金细化剂。系统研究了预制块中Al 粉含量、C/Ti 比、Al 液温度等工艺参数对所制备的晶粒细化剂组织的影响。研究结果表明: 直接SHS 工艺合成的细化剂由Al 和亚微米TiC 粒子组成,而铝液中的SHS 工艺制备的细化剂则由Al、块状Al3Ti 和粒状TiC组成。比较分析了上述两种工艺制备的晶粒细化剂分别对工业纯Al 的晶粒细化效果和抗晶粒细化衰退能力。细化实验表明,上述两种工艺制备的细化剂对工业纯铝均有良好的晶粒细化效果和较高的抗晶粒细化衰退能力。但从工艺和经济的角度来看,铝液中的SHS 工艺更适合Al-Ti-C 晶粒细化剂的工业生产。更多还原

【Abstract】 Compared with conventional Al-Ti-B master alloy, Al-Ti-C grain refiner has little limitations existed in Al-Ti-B master alloy. For example, Al-Ti-B grain refiner has the larger TiB2 particles. In addition, TiB2 particles also tend to be poisoned by elements Zr, Cr or Mn in aluminum melt and to lose their refining effectiveness. Therefore, it has been generally accepted that Al-Ti-C master alloys with TiC particles are considered to be the most promising grain refiner for aluminum and its alloys, But because of poor wettability of carbon with molten aluminum, the grain refiner can not been fabricated steadily by the way of ecumenical melting. Studying new preparation technology of the grain refiner is always the seeking target by people. In order to reach the target, the paper puts forward a new technics of fabricating the grain refiner -Self-propagating high-temperature synthesis (SHS) technology. The reaction energetics of Al-Ti-C system have been theoretically analyzed and calculated based on solution thermodynamic theory at first. The results indicate: Al-Ti-C perform dipped into the melt can be ignited the combustion synthesis reaction by the inherent heat of an elevated temperature Al-melt. And can gain needed Al3Ti and TiC of grain refiner. Fabricating Al-Ti-C master alloys grain refiners based on self-propagating high-temperatuer synthesis (SHS) technology in molten Al is promising. Al-Ti-C grain refiners have been fabricated by the direct self-propagating high-temperature synthesis (SHS) technology and self-propagating high-temperatuer synthesis (SHS) technology in molten Al. The effects of the temperature of the melt and the composition of the mixture on the microstructrues of the fabricated master alloys were studied systemically. The research results indicate that Al-Ti-C grain refiners synthesized directly by SHS technology consist of Al matrix and submicron-sized TiC particles, whereas the grain refiners fabricated by SHS in molten Al contain three phases of Al, Al3Ti and TiC. The refining performances for commercially pure aluminum and resistance to grain refining fading of the Al-Ti-C master alloys fabricated respectively by above two techniques have been compared by refining experiments. The refining experiments indicate the grain refiners fabricated respectively by above two techniques exhibit excellent grain-refining performances for commercially pure aluminum and high resistance to grain refining fading. However, in view of production cost and technical features of the grain refiners, it is found that SHS technique in molten Al is more suitable for the industry producing of the grain refiners.更多还原