【作者】 杨秀青；

【导师】 孙康宁；

【作者基本信息】 山东大学 ， 材料学， 2011， 硕士

【摘要】 陶瓷因具有高强度、高硬度、耐磨性、耐腐蚀性、电绝缘性等特性,被广泛地应用在日常生活、工业生产以及高科技领域,但韧性低一直是阻碍其进一步应用的重要原因。因此,对于如何改善陶瓷的韧性和制备具有非常重要的意义。多年来,人们通过各种增韧手段来改善陶瓷的韧性,常用的增韧方式有颗粒弥散增韧、纤维和晶须增韧、氧化锆相变增韧、复合增韧与自增韧等。目前,NiTi形状记忆合金因具有丰富的相变现象,已广泛应用在航天航空、建筑、生物医学及日常生活等领域。本文选用氧化铝陶瓷为基体,NiTi合金颗粒为第二相,将其复合到氧化铝陶瓷基体中,利用NiTi合金的马氏体相变(形状记忆效应和超弹性均是由其来体现)改善氧化铝陶瓷的韧性。本文采用CMT5105型微机控制电子万能试验机研究了NiTi合金对氧化铝陶瓷抗弯强度和断裂韧性的影响；采用HD-1875型布洛维硬度计研究了复合陶瓷硬度；采用X射线衍射仪研究了复合陶瓷的物相组成；采用扫描电子显微镜对复合陶瓷材料的断口形貌进行观察分析,并对增韧机理进行探讨。本文利用机械合金化法制备非晶NiTi合金粉末,经晶化处理后,使其均匀分散到氧化铝陶瓷基体中,采用热压烧结工艺,在1300℃和1400℃的烧结温度下制备复合陶瓷。同时选用等原子比的NiTi合金加入到氧化铝陶瓷基体中,在13000℃的烧结温度下制备复合陶瓷；与相同温度下加入机械合金化制备NiTi合金的复合陶瓷的性能作对比。研究表明：利用机械合金化法可制得非晶NiTi合金粉末,晶化处理后可得到晶体结构为体心立方的NiTi合金；将晶化处理后得到的合金粉末加入到氧化铝陶瓷基体中,在1300℃和1400℃烧结温度下制备复合陶瓷,随着加入合金含量的增加,复合陶瓷的抗弯强度和断裂韧性均有明显的提高。将等原子比的NiTi合金加入到氧化铝陶瓷基体中,在1300℃的烧结温度下制备复合陶瓷,随着NiTi合金含量的不断增加,复合陶瓷的力学性能也不断地提高,但硬度变化不大；与1300℃的烧结温度下加入机械合金化制备NiTi合金的复合陶瓷的性能相比,加入等原子比的NiTi合金的复合陶瓷的性能较好,这主要是因为在混料过程中,延长了混料时间,使合金在试样中的分散性得到改善,提高烧结试样的致密度,从而提高复合陶瓷的强度和韧性。研究结果表明：受到外力的作用时,复合陶瓷中的NiTi合金发生应力诱导相变,相变过程中产生的体积膨胀会消耗裂纹扩展的能量,抑制裂纹扩展并使裂纹发生偏转,提高复合陶瓷断裂韧性；同时NiTi合金颗粒的桥联作用可抑制裂纹的继续扩展,改善陶瓷韧性。更多还原

【Abstract】 Ceramic has high strength, high hardness, wear resistance, corrosion resistance, electrical insulation features, so it is widely used in daily life, industrial production and high-tech fields, but the roadblock to its application is poor fracture toughness. Therefore, how to improve ceramic toughness and preparation has the extremely vital significance.Over the years, the people through various toughening methods to improve ceramic toughness. The common toughening methods have particle dispersion toughening, fiber and whisker toughening, zirconia phase transformation toughening, composite toughening and self-toughening, etc.At present, because NiTi shape memory alloy with rich phase transition phenomenon, so it is widely used in aerospace, architecture, biomedical and daily life, etc. This paper selects alumina ceramics as substrate, NiTi alloy particles as the second phase composite to alumina ceramic substrate. Through the NiTi alloy martensite transformation to improve the characteristics of alumina ceramic toughness.In this paper, the effect of NiTi alloy on alumina ceramic flexural strength and fracture toughness were tested with a CMT5105 Electromechanical universal testing machine;A HD-1875 hardness testing machine was employed to test the hardness of the composite ceramic;this paper researched the phase composition of composite;by scanning electron microscope to observe and analyze the fracture morphology of ceramic materials, and discuss the toughening mechanism.This paper prepared amorphous NiTi alloy powder by mechanical alloying. After the crystallization processing, made the alloy dispersed homogeneously to alumina substrate. Under 1400℃and 1300℃sintering temperature prepared composite ceramic by hot-press sintering process. Meanwhile this paper made equiatomic NiTi alloy composited to alumina substrate, under 1300℃sintering temperature prepared composites. In the meantime, this paper contrasted their mechanical property to the composite ceramics which were composited NiTi alloy by mechanical alloying.The result indicates that mechanical alloying can prepare amorphous NiTi alloy powder and obtain NiTi alloy which crystalline strcture is body centered cubic after the crystallization. This paper made the alloy powder composited to alumina substrate. Under 1400℃and 1300℃sintering temperature prepared composites, their flexural strength and fracture toughness were obviously improved with the increase of the content of NiTi alloy powder. In the same time, this paper made equiatomic NiTi alloy powder composited to alumina substrate, under 1300℃sintering temperature prepared composites, which mechanical properties constantly improved with the increase of the content of alloy powder, but the hardness remained almost unchanged. Compared to the composites whose second phase was NiTi alloy powder which prepared by mechanical alloying, the mechanical properties of the composites whose second phase was equiatomic NiTi alloy powder were better. Because in mixing process we extended the mixing time which could make alloy powder equably dispersed in alumina substrate, and this could improve the composites density, so the composites strength and toughness could be enhanced.The results of the study show that:when external force in composites, NiTi alloy produced stress induced phase transition. The volume dilatancy in phase transition process could consume energy of crack propagation, in the same time, it could restrain the crack propagation and make the crack deflection which improved the composites fracture toughness;Meanwhile NiTi alloy particle bridge league action could inhibit crack continue to expand and improve the composites toughness.更多还原