Nb-Cr掺杂原位合成Al2O3/TiAl复合材料的组织与性能

采用原位热压工艺,在Ti-Al-TiO2-Nb2O5体系中加入Cr2O3原位合成Al2O3/TiAl复合材料.借助X射线衍射分析、SEM分析及力学性能分析,研究了Nb-Cr掺杂复合强化Al2O3/TiAl复合材料的反应过程、微观结构及力学性能.结果表明Nb-Cr掺杂原位合成Al2O3/TiAl复合材料能够细化晶粒并通过微合金化增强增韧TiAl复合材料.     

Sm_2O_3掺杂强韧化TiAl复合材料

以Ti,Al,TiO2和Sm2O3为原料,利用原位合成法制备Al2O3/TiAl复合材料;并借助XRD、SEM和力学性能测试,研究Sm2O3掺杂对Al2O3/TiAl复合材料微观结构和力学性能的影响。结果表明：掺杂Sm2O3的Al2O3/TiAl复合材料由γ-TiAl/α2-Ti3Al基体相以及Al2O3、SmAl增强相组成;掺杂Sm2O3细化了复合材料的微观结构,改善了TiAl复合材料的力学性能;当Sm含量为5%（质量分数）时,该复合材料的弯曲强度和断裂韧性达到最大,分别为658.9MPa和10.13MPa·m1/2。     

载荷对钛合金Al2O3Y2O3/AlY复合涂层摩擦学性能的影响

为了提高耐摩擦磨损性能,采用磁控溅射技术在γTiAl钛合金表面制备了Al2O3Y2O3/AlY复合涂层。检测了涂层的厚度、表面硬度、微观组织和成分变化。通过在130g、230g和330g载荷下采用GCr15钢球作摩擦副进行的摩擦磨损试验,研究了有和无复合涂层的γTiAl合金的耐摩擦磨损性能。结果表明:Al2O3Y2O3/AlY复合涂层的厚度约为33μm,由Al2O3Y2O3层、AlY层和扩散层组成,平均表面硬度为433.4HV0.1。带复合涂层的γTiAl合金摩擦因数和比磨损率均比无涂层γTiAl合金的小。在不同的摩擦磨损试验载荷下,无涂层γTiAl合金的磨损机制为磨粒磨损和黏着磨损,而有Al2O3Y2O3/AlY复合涂层的γTiAl合金则主要是磨粒磨损和氧化磨损。     

Fe-Al/Al2O3复合材料抗热震性研究

采用测硬度和抗压强度的方法，测定了Fe-Al/Al2O3复合材料的抗热震性。结果表明Fe-Al/Al2O3复合材料的临界热震温差在800℃左右，抗压强度可以较好地反映材料的抗热震性。同时对循环热震后Fe-Al/Al2O3复合材料进行了XRD分析，表明该材料在循环热震中存在有序截留、氢脆和氧化现象。最后用热震理论分析了Fe-Al/Al2O3复合材料的抗热震机理。     

Al2O3纤维对Al2O3基陶瓷型芯材料性能的影响

采用常压烧结制备Al2O3基陶瓷型芯材料，通过XRD，SEM分析表征了材料的成分和内部结构。测量了Al2O3基陶瓷型芯气孔率、抗蠕变性能、80℃饱和NaOH溶液中侵蚀性能，并讨论了材料性能随Al2O3纤维含量变化的原因。     

SiO2涂层对TiAl基合金抗高温氧化性能的影响

采用SiO2溶胶-凝胶-旋涂法对TiAl基合金表面进行涂膜。900℃循环氧化测试结果表明,TiAl基合金经SiO2溶胶两次涂膜并热处理后,其抗高温氧化性能得到了显著提高,未涂膜试样氧化一个循环（8h）后增重2.333mg/cm^2,涂膜热处理试样氧化40个循环（320h）增重仅为0.6071mg/cm^2。XRD和SEM对试样表层的组织结构分析及形貌观察表明,涂层主要由SiO2、Al2O3、Ti5Si3、TiSi2和Ti2Al构成,由表及里分别为SiO2层-Al2O3层-Al2O3＋钛硅化合物层-Ti2Al层-TiAl片层组织基体。     

Al2O3/TiAl复合材料的原位合成及反应机制的研究

利用Al-Ti-TiO2体系的放热反应,原位合成了Al2O3/TiAl复合材料.借助示差热分析法探讨了体系的反应机制,采用XRD、SEM和OM分析了复合材料的相组成及显微组织.结果表明,原位合成Al2O3/TiAl复合材料由TiAl、Ti3Al和Al2O3相组成,Al2O3颗粒分布于TiAl和Ti3Al双相交界处,并存在一定团聚.随其含量增加,团聚程度加剧,晶粒尺寸减小.Ti和Al反应生成TiAl3放出的热量使部分TiAl3相处于液相状态,熔融的体积分数约为87.87%,液相的存在提高了颗粒间的润湿性,同时放出的热量是引发后续反应的原因之一.TiAl3与Al-TiO2的还原反应生成的活性Ti原子结合最终生成了TiAl和Ti3Al相.     

合金上置熔渗法制备Al2O3/Al复合材料

采用合金上置熔渗法制备Al2O3/Al复合材料，观测组织结构和相组成，分析助渗工艺及气氛的作用。结果发现，破坏铝合金液表面氧化膜是浸渗进行的关键因素，在合金底面添加Al2（SO4）3粉末，高温下分解放出大量气体，可以冲破底面Al2O3膜，使浸渗得以进行。采用氮气气氛保护有利于获得组织致密、相间界面结合良好的复合材料。     

等离子喷涂CoNiCrAlY+(ZrO2+Y2O3)涂层在TiAl合金表面的应用

用等离子喷涂法在TiAl合金基体表面依次喷涂CoNiCrAlY涂层和(ZrO2 Y2O3)陶瓷障涂层，对处理后的TiAl合金进行高温氧化试验，结果表明，其高温抗氧化能力提高．并用XRD、SEM检测了试样的金相组织、结果及形貌。     

Al2O3纤维对Al2O3基陶瓷型芯材料性能的影响

采用常压烧结制备Al2O3基陶瓷型芯材料,通过XRD,SEM分析表征了材料的成分和内部结构.测量了Al2O3基陶瓷型芯气孔率、抗蠕变性能、80℃饱和NaOH溶液中侵蚀性能,并讨论了材料性能随Al2O3纤维含量变化的原因.     

Reaction procedure of a graphite fiber reinforced Ti-Al composite produced by squeeze casting-in situ reaction

The in situ reaction procedure and microstructure evolution of a graphite fiber reinforced Ti-Al composite (Grf/Ti-Al) was investigated, and the stability of TiAl3 at high temperature was discussed. As-cast material was prepared by pressing molten pure aluminum into a preform, which was composed of titanium particles and graphite fibers. The in situ reaction procedure of the as-cast material was investigated by differential scanning calorimetry (DSC), and phases in the products were detected by X-ray diffraction (XRD). Experimental results showed that TiAl3 was formed first. With an increase in temperature, TiC and Al4C3 were observed, but TiAl3 decreased. In the final product, Al2O3 and TiO2 were observed. It was considered that the previous forming TiAl3 decomposed, then TiC precipitated, and subsequently, oxidation resulted in the formation of Al2O3 and TiO2.     

Effects of Nb and Si on high temperature oxidation of TiAl

The isothermal oxidation behavior of TiAl based alloys at 900℃ in air with a combination of Nb (5%-10%, mole fraction) and Si (1%-5%, mole fraction) was investigated. The microstructure and the composition of the oxidation scale were studied by using XRD, TEM and EPMA. The results show that the combination of Nb and Si can improve the oxidation resistance of the alloys significantly. The element Si can change the typical microstructure of oxidation scale on TiAl based alloys. In alloys with Si addition, the compact Al2O3 forms in the interior side of oxidation scale. When x (Si)3%, the Ti5Si3 phase forms and the coarse crystal TiO2 forms on Ti5Si3 phase after oxidation. The increase of Nb content in the TiAl based alloys impedes the growth of Ti5Si3 phase, and the formation of TiO2 on surface and on Ti5Si3 phase is also impeded.     

MICROSTRUCTURES AND MECHANICAL PROPERTIES OF IN-SITU Al2O3/TiAl COMPOSITES BY EXOTHERMIC DISPERSION METHOD

In-situ Al2O3/TiAl composites were fabricated by pressure-assisted exothermic disper-sion (PAXD) method from elemental powder mixtures of Ti, Al, TiO2, and Nb2O5.The microstructures and mechanical properties of the as-sintered composites are in-vestigated. The results show that the as-sintered products consist of γ-TiAl, α2-Ti3Al,Al2O3, and NbAl3 phases. Microstrueture analysis indicates that Al2O3 particles tend to disperse on the grain boundaries. Application of a moderate pressure of 35 Mpa at 1200℃ yields Ab2O3/TiAl composites with fine Al2O3 reinforcement and a dis-continuous network linking by Al2O3 particles. The aluminide component has a fine submicron γ+α2 larnellar rnicrostructure. With increasing Nb2O5 content, A1203 par-ticles are dispersed uniformly in the matrix. The hardness of the composites increases gradually, and the bending strength and fracture toughness of the composites reach to the maximum value, respectively.     

Ti-Al-TiO_2体系的热力学分析及合成反应过程研究

以Ti、Al和Ti02混合粉的原位反应制备Al203颗粒增强TiAl基复合材料.利用热力学机理分析了制备该种材料的可行性;用扫描电镜观察了合成产物的组织形态;借助差热变化曲线,对Ti-Al-Ti02体系的反应过程进行了初步研究.结果表明,Ti-Al-Ti02体系的反应能够原位生成Al203颗粒增强的TiAl基复合材料;Al203颗粒分布在基体晶界处,随其含量增大,基体晶粒逐渐细化;铝熔化后首先开始了TiAl3的生成反应,由于Ti02的稀释作用,使它的放热峰与Ti-Al体系的主放热峰相比有所滞后,紧接着发生了Al-Ti02的还原反应,由于其激活能低而速度较快,因此较早完成;若Al-Ti02的还原反应未进行彻底,部分TiAl3将分解以提供铝液;最后发生了TiAl3向TiAl和TiAl相转变的过程.     

反应等离子喷涂AlNbO4-Al2O3-NbOx复合涂层的研究

目的研究等离子喷涂Al-Nb_2O_5铝热体系制备的AlNbO_4-Al_2O_3-NbO_x复合涂层的组织、力学性能和摩擦磨损性能。方法以Nb_2O_5粉和Al粉为原料,通过喷雾造粒制备复合粉,采用等离子喷涂技术喷涂Al-Nb_2O_5复合粉体,利用复合粉的自反应制备出含有AlNbO_4、Al_2O_3和NbO_x的复合陶瓷涂层。利用扫描电镜、EDS和XRD检测和分析复合涂层的组织和物相。用显微硬度计测定复合涂层的硬度,并用硬度压痕法测量裂纹扩展能(Gc)。用销盘式磨损试验机测定涂层在无润滑条件下的摩擦磨损性能。结果 XRD分析可知,复合涂层由AlNbO_4、Al_2O_3和NbO_x相组成,SEM显示涂层为交替分布的层片状组织。在28~32 k W功率范围内,随着喷涂功率的升高,涂层的硬度增加,喷涂功率为32 k W时,涂层硬度最高,为912HV0.1。随着喷涂功率的升高,涂层的裂纹扩展能先升高后降低,喷涂功率为30 k W时,涂层的裂纹扩展能最大,为14.14J/m2。摩擦系数随功率的升高先降低后保持不变,28 k W时,涂层的摩擦系数为0.7~0.8,30 k W和32 k W时,涂层的摩擦系数为0.5~0.6。磨损量随喷涂功率的增加先降低后升高,喷涂功率为30 k W时,涂层的磨损量最小。磨损后的试样进行SEM检测发现有明显的犁沟、凹槽和剥落。结论涂层具有由AlNbO_4、Al_2O_3和NbO_x相组成的交替分布的多相层片状组织。喷涂功率为30 k W时,复合涂层的性能最好。复合涂层的主要磨损机制为磨粒磨损和疲劳磨损。     

ZrB2/Al2O3 composite powders prepared by self-propagating high-temperature synthesis

Self-propagating high-temperature synthesis（SHS） method was used to synthesize ZrB2/Al2O3 composite powders from B2O3-ZrO2-Al system. X-ray diffractometry（XRD） and scanning electron microscopy（SEM） analyses show the presence of ZrB2 and Al2O3 as the primary phases in the composite powders, while the presence of a very small amount of ZrO2 is thought to be unreacted zirconium oxide. Transmission electron microscopy（TEM） and high resolution electron microscopy（HREM） observations of microstructure of the composite powders indicate that the interfaces of ZrB2/Al2O3 bond well without any interracial reaction products. It is proposed that the good interfacial bonding of composite powders results from the ZrB2 particles crystallizing and growing on the Al2O3 particles surface with surface defects acting as nucleation centers.     

Microstructures And Mechanical Properties Of In-Situ Al2o3/Tial Composites By Exothermic Dispersion Method

In-situ Al2O3/TiAl composites were fabricated by pressure-assisted exothermic dispersion （PAXD） method from elemental powder mixtures of Ti, Al, TiO2, and Nb2O5. The microstructures and mechanical properties of the as-sintered composites are investigated. The results show that the as-sintered products consist of γ-TiAl, α2-Ti3Al, Al2O3, and NbAl3 phases. Microstructure analysis indicates that Al2O3 particles tend to disperse on the grain boundaries. Application of a moderate pressure of 35 MPa at 1200℃ yields Al2O3/TiAl composites with fine Al2O3 reinforcement and a discontinuous network linking by Al2O3 particles. The aluminide component has a fine submicron γ ＋α2 lamellar microstructure. With increasing Nb2O5 content, Al2O3 particles are dispersed uniformly in the matrix. The hardness of the composites increases gradually, and the bending strength and fracture toughness of the composites reach to the maximum value, respectively.     

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 利用双向脉冲复合电沉积技术制备Ni/Al₂O₃复合镀层，并用X射线衍射（XRD）、扫描电镜/能谱（SEM/EDS）及性能测试等方法研究了复合镀层的组织与硬度。结果表明：采用双向脉冲电沉积技术可获得结晶细密且表面光滑平整的Ni/Al₂O₃复合镀层。在本试验范围内，镀层的硬度随着Al₂O₃含量的增加而升高。     

放电等离子烧结的钛铝合金组织及氧化性能研究

研究了TiH2-45Al-0.2Si-5Nb未球磨和球磨两种粉末的放电等离子烧结组织特征以及经1000℃、100h高温氧化后的氧化性能.结果表明,未经球磨粉末的烧结组织由层片状TiAl和Ti3Al相组成,而经球磨粉末的烧结组织由细小的颗粒状TiAJ和Ti3Al相组成.球磨粉末的烧结组织氧化速度低于未球磨粉末的烧结组织,形成了连续的Al2O3和TiO2混合氧化物层,具有良好的高温抗氧化性.