La2O3含量对Al2O3/Cu基复合材料组织与性能的影响

以La₂O₃粉、Al粉、CuO粉为反应物原料、纯铜为基体,采用原位合成技术和近熔点铸造法制备颗粒增强Cu基复合材料,研究La₂O₃对Al-CuO体系制备的Cu基复合材料组织及性能的影响。结果表明：添加La₂O₃可获得纳米Al₂O₃颗粒,且弥散分布于Cu基体中,制备的材料组织更加细小、均匀,其材料的电导率及摩擦磨损性能明显提高。当添加0.6%wtLa₂O₃,复合材料的电导率达到90.2%IACS,磨损量达到最小,相比未添加La₂O₃,其导电率提高10.1%,磨损量减小36.6%。     

BN/Al2O3 复合粉末及其聚合物基复合材料的制备与导热性能

采用固-液相共混法制备了多种BN/Al₂O₃复合粉末,通过冻融法和表面修饰法对BN进行了改性处理,改变表面修饰剂类型和摩尔比得到了前驱体和烧结态BN/Al₂O₃复合粉末,并利用机械混合法制备了聚合物基BN/Al₂O₃复合材料,并测试分析了其导热性能。结果表明,经冻融处理的BN分散性和界面相容性明显优于未经冻融处理的BN。多巴胺对BN的改性效果优于聚乙二醇。采用多巴胺作为表面修饰剂且BN与Al(NO₃)₃的摩尔比为1:1时,能够得到纳米Al₂O₃均匀包覆的微米BN粉末,即BN/Al₂O₃微纳复合粉末,其聚合物基复合材料的导热系数可达0.62 W·m^-1·K^-1,是纯聚合物导热系数的3倍,是采用纯微米BN粉末制备的聚合物基复合材料导热系数的1.5倍。在BN表面附着的Al₂O₃可以形成层状热传导通道,能够有效提高聚合物基BN/Al₂O₃复合材料的热导率。     

La2O3掺杂氧化铝气凝胶的制备与耐温性能研究

以仲丁醇铝为前驱体,采用溶胶-凝胶法结合丙酮-苯胺原位生成水技术,通过乙醇超临界干燥,制备出不同含量(1.5 mol%~12 mol%)La₂O₃掺杂的氧化铝气凝胶。采用电子扫描电镜(SEM)、透射电子显微镜(TEM)、X线衍射仪(XRD)、N₂吸附分析仪等仪器表征了La₂O₃掺杂对氧化铝气凝胶的微结构和耐温性能的影响。结果表明：La₂O₃的引入使氧化铝气凝胶的形貌由球状颗粒向大的片状结构转变。适量的La₂O₃掺杂能提高氧化铝气凝胶的比表面积,9 mol% La₂O₃掺杂的氧化铝气凝胶比表面积最大。通过La₂O₃掺杂,能够抑制氧化铝晶粒在高温下的生长和α-Al₂O₃的相变,提高氧化铝气凝胶的耐温性能。1200℃热处理后,La₂O₃掺杂的氧化铝气凝胶仍维持在θ-Al₂O₃,比表面积为86.5 m₂/g,高于未掺杂的氧化铝气凝胶(46 m₂/g)。     

La2O3掺杂AgSnO2电接触材料的制备及性能研究

以Ag、Sn、La₂O₃粉为原料,采用机械合金法制备复合粉体。结合氧化法与粉末冶金工艺,对复合粉体进行氧化、压制、烧结。采用扫描电镜(SEM)和能谱仪、硬度计、金相显微镜、金属电导率测量仪等对复合粉体氧化前后的形貌以及电接触材料烧结前后的性能进行表征。结果表明：烧结后,电接触材料硬度较于烧结前明显下降。同时电接触材料随Sn含量增大,电阻率升高,密度反而下降。在一定的La₂O₃(0wt.%、0.75wt.%、1.5wt.%、2.25wt.%、3wt.%)含量范围内,La₂O₃掺杂量越高,密度越低。同时电接触材料经烧结后,随La₂O₃含量增加,其电阻率先降后升,在La₂O₃含量为0.75wt.%时,电接触材料的电阻率最低。     

γ-TiAl合金表面Al2O3/Al复合涂层的抗高温熔盐腐蚀性能研究

采用磁控溅射技术于γ-TiAl合金表面制备Al₂O₃/Al复合涂层。在850 °C下、 100 wt.% Na₂SO₄熔盐中观测Al₂O₃/Al复合涂层的高温腐蚀行为。结果表明,Al₂O₃/Al复合涂层具备由Al₂O₃表层、富Al中间层以及互扩散层组成的梯度结构,因而有效地提高了基体γ-TiAl合金的抗高温腐蚀性能。在腐蚀实验后,涂层试样表面相结构为Al₂O₃,TiO₂和TiAl₃。致密的Al₂O₃/Al复合涂层有效地抑制了O_2-,S_-和Na₊对基体γ-TiAl合金的侵蚀。并且,Al₂O₃/Al复合涂层的梯度结构亦使其表现出了优异的抗开裂和抗剥落性能。     

原位颗粒对近液相线铸造6063铝合金微观组织和耐磨性的影响机理

以CuO-Al作为反应体系,在6063铝合金中原位反应生成Al₂O₃颗粒,采用近液线相铸造的方法制备6063Al-XAl₂O₃(X=0,2,4,6)复合材料。研究原位反应颗粒Al₂O₃与6063铝合金自带的原位结晶颗粒Mg₂Si的形状、尺寸、数量、分布、界面特征等对合金微观组织和耐磨性的影响机理。结果表明,在6063铝合金中原位反应生成尺寸在亚微米级的近球形θ-Al₂O₃颗粒;其(311)晶面与6063铝合金基体(111)晶面成共格界面;6063铝合金中Mg₂Si尺寸大约为100nm,呈条带状,其(02-2)与Al基体(111)晶面属于共格界面。随着Al₂O₃颗粒含量的增加,6063铝基复合材料的晶粒组织形貌由蔷薇状逐渐向等轴晶转变,晶粒尺寸逐渐减小。当Al₂O₃的质量分数为6%时,复合材料组织由等轴晶和细小的柱状晶组成。载荷为50N时,6063铝合金的磨损量为6.72mg,6063-6Al₂O₃复合材料的磨损量为1.63mg,相对于6063铝合金降低75.7%。原位颗粒(Al₂O₃+Mg₂Si)与铝基体都成共格界面,界面之间无污染,界面结合强度高,在磨损过程中,不易从基体中脱落,承当磨损过程中的大部分载荷。原位生成高硬度的Al₂O₃颗粒与原位结晶颗粒Mg₂Si协同作用共同提高复合材料的耐磨性。外加载荷为40N时,随着增强相质量分数的增加,复合材料的磨损机制由粘着磨损转变为磨粒磨损。6063铝合金磨损机制以严重的粘着磨损为主。6063-2Al₂O₃复合材料磨损机制主要以粘着磨损为主,6063-4 Al₂O₃和6063-6Al₂O₃复合材料主要表现为磨粒磨损。     

Al0.7Sb2Te3三元靶材的结构性能表征

以原子比Al:Sb:Te=0.7:2:3的混和粉为原料,采用真空合成法与烧结-热等静压制备Al_0.7Sb₂Te₃三元靶材,通过XRD、FESEM、EDS、XPS等手段表征其性能,且重点采用XPS研究Al在Al_0.7Sb₂Te₃三元靶材的存在状态。结果表明：Al掺杂后,靶材主相Sb₂Te₃的晶格常数减小,且单质Al弥散相与Al_0.1Sb₂Te₃基体相共存,表明掺杂对靶材的组织结构确有影响;刻蚀深度从0增加至405.9nm,Al价态从以Al₂O₃的化合态为主逐渐过渡至以单质态为主,且Al以Al₂O₃形态为主的区域深度约90nm;刻蚀深度为405.9nm时,来自非氧化物的Al价态与来自AlSb的Sb价态联合表明：Al_0.1Sb₂Te₃中的Al通过有效化合形成AlSb影响着靶材的组织结构。     

三元共晶成分Al2O3/YAG/ZrO2粉体及陶瓷的制备与组织性能研究

本文采用醇水共沉淀法制备了三元共晶成分Al₂O₃/YAG/ZrO₂粉体,在600-1350_oC温度范围煅烧后研究其物相转变过程。经1300_oC煅烧后Al₂O₃/YAG/ZrO₂共晶成分粉体的物相由α-Al₂O₃、c-ZrO₂和YAG构成,且具有α-Al₂O₃相包裹c-ZrO₂相的特殊结构。将煅烧粉体在1550_oC下热压烧结,制备具有内晶型结构的共晶成分Al₂O₃/YAG/ZrO₂复相陶瓷,其致密度、室温抗弯强度、断裂韧性和高温(1000_oC)抗弯强度分别为98.8%、420 MPa、3.69 MPa.m_1/2和464 MPa,并对复相陶瓷组织结构的形成机理进行了探讨。     

Al2O3微粉添加量对镁合金微弧氧化膜特性影响研究

为了研究添加Al₂O₃微粉对AZ31A镁合金微弧氧化膜特性影响,在不同浓度Al₂O₃微粉电解液中对其进行了微弧氧化处理。利用扫描电镜(SEM)观察微弧氧化膜形貌,能谱仪(EDS)分析了膜层表面Ca、Mg、O、Al元素分布,X射线衍射仪(XRD)分析了相组成,测定了膜厚、硬度和氧化液中Al₂O₃表面电荷,讨论了掺杂改性机理。结果表明,加入Al₂O₃微粉后,氧化电压随Al₂O₃添加量增加先增加后降低;氧化膜表面孔洞数量和尺寸减小,膜层表面Ca元素分布逐渐减少,成膜效率降低,膜层致密度和表面疏松层硬度提高,氧化膜主要由MgO和MgO₄等相组成。     

Al2O3/Ti2AlN复合材料在900℃,1000℃和1100℃空气中的氧化行为

利用综合热分析仪、背散射扫描电镜(BSE)和能谱分析(EDS)对Al₂O₃/Ti₂AlN复合材料在900 ℃,1 000 ℃和1 100 ℃/20 h空气中连续氧化20h后的氧化增重及氧化层截面进行了研究。结果表明：Al₂O₃/Ti₂AlN复合材料在空气中的氧化行为符合抛物线规律,在900 ℃,1 000 ℃和1 100 ℃/20 h氧化增重分别为2.78×10_-2 kg/m₂、10.4 ×10_-2 kg/m₂、21.9 ×10_-2 kg/m₂,抛物线速率常数相应为1.08×10_-8 kg₂/m₄s、1.44×10_-7 kg₂/m₄s、6.56×10_-7 kg₂/m₄s,氧化激活能为274 kJ/mol。氧化层主要由TiO₂和Al₂O₃组成的,连续的Al₂O₃次外层可以提高其抗氧化性能。氧化层结构的改变是由于氧化温度对Ti₄₊、Al₃₊由基体表面向外扩散和O_2-向内扩散的影响,以及TiO₂和Al₂O₃在不同温度下的形核生长速率导致的。对Al₂O₃/Ti₂AlN而言,控制材料与氧化气氛的界面是提高该材料抗氧化性能的关键。     

Ti活度对Al2O3/AgCuTi/Fe-Ni-Co钎焊接头机械性能和微观组织结构的影响

采用AgCuTi钎料实现了Al₂O₃陶瓷与Fe-Co-Ni合金的钎焊连接,并调查了不同钛含量的钎料对Al₂O₃/AgCuTi/Fe-Ni-Co钎焊接头机械性能和微观组织结构的影响。扫描电子显微镜(SEM), X射线能量色散光谱仪(EDS), X射线衍射仪(XRD)及电子万能试验机用于分析钎焊接头的机械性能和微观组织结构,结果表明:钛含量的增加明显提高AgCuTi钎料与Al₂O₃陶瓷的相互作用,在Al₂O₃/Ag-Cu-Ti界面生成一层由Ti-Al 和 Ti-O化合物组成的反应层。Al₂O₃/AgCuTi/Fe-Ni-Co钎焊接头的抗拉强度随钛含量的增加而增加,当钛含量提高到8wt.%时,抗拉强度达到最大值78Mpa。通过微观组织结构分析发现,采用AgCu4Ti在890℃保温5min的条件下可以获得较好的钎焊接头,典型接头的微观组织结构为Al₂O₃/TiAl+Ti₃O₅/NiTi+Cu₃Ti+Ag(s,s)/Ag(s,s)+Cu(s,s)+(Cu,Ni)/Fe-Ni-Co。采用AgCu8Ti获得的钎焊接头的界面反应层与AgCu4Ti差异不大,但反应层稍微增厚,并伴有TiO和Ti3Al在Al₂O₃/Ag-Cu-Ti界面生成。     

Influences of annealing temperature on microstructure and mechanical properties of Mo-La2O3

Influences of annealing temperature on the microstructure and mechanical properties of Mo-La₂O₃ were investigated. Effects of annealing temperature on tensile properties, fracture toughness, and microhardness are discussed. Microstructure and fracture morphology of Mo alloys are observed by optical microscope, SEM, and TEM. The results indicate that grain size increased while tensile strength, fracture toughness, and microhardness decreased with increasing annealing temperature. Larger La₂O₃ particles are located at grain boundaries or sub-boundaries, while the majority of smaller La₂O₃ particles are located within the grain. The strengthening effect is quantitatively assessed, which yielded a predicted yield strength in good agreement with measurements.     

Examination of wire electrical discharge machining of Al2O3p/6061Al composites

Alumina particle reinforced 6061 aluminum matrix composites (Al₂O₃p/6061Al) have excellent physical and chemical properties than those of a traditional metal; however, their poor machinability lead to worse surface quality and serious cutting tool wear. In this study, wire electrical discharge machining (WEDM) is adopted in machining Al₂O₃p/6061Al composite. In the experiments, machining parameters of pulse-on time were changed to explore their effects on machining performance, including the cutting speed, the width of slit and surface roughness. Moreover, the wire electrode is easily broken during the machining Al₂O₃p/6061Al composite, so this work comprehensively investigates into the locations of the broken wire and the reason of wire breaking.The experimental results indicate that the cutting speed (material removal rate), the surface roughness and the width of the slit of cutting test material significantly depend on volume fraction of reinforcement (Al₂O₃ particles). Furthermore, bands on the machined surface for cutting 20 vol.% Al₂O₃p/6061Al composite are easily formed, basically due to some embedded reinforcing Al₂O₃ particles on the surface of 6061 aluminum matrix, interrupt the machining process. Test results reveal that in machining Al₂O₃p/6061Al composites a very low wire tension, a high flushing rate and a high wire speed are required to prevent wire breakage; an appropriate servo voltage, a short pulse-on time, and a short pulse-off time, which are normally associated with a high cutting speed, have little effect on the surface roughness.     

Strengthening and toughening forming of Al/Al2O3 composite in pseudo-semi-solid state

A new technology—thixo-die-forging of the composite in pseudo-semi-solid state was proposed based on the powder metallurgy technology combing with semi-solid metal process, and the cup shells with Al/Al₂O₃  composite was prepared successfully. The metallographic analysis and performance test show that the microstructure of parts is dense and mechanical properties are excellent with the volume fraction of Al is 37 %. The bend strength and fracture toughness of the composite are about 570-690 MPa and 8.5-16.8 MPa m^1/2, respectively. Comparing with reaction in situ and high temperature oxidation technologies the bending strength and fracture toughness are improved greatly. At the same time, it shows that the technology parameters have great influences on the properties. So it is feasible to prepare metal/ceramics composites by the proposed technology.     

Bulk WC-Al2O3 composites prepared by spark plasma sintering

WC and WC-Al₂O₃ materials without metallic binder addition were densified by spark plasma sintering in the range of 1800-1900 °C. The densification behavior, phase constitution, microstructure and mechanical properties of pure WC and WC-Al₂O₃ composite were investigated. The addition of Al₂O₃ facilitates sintering and increases the fracture toughness of the composites to a certain extent. An interesting phenomenon is found that a proper content of Al₂O₃ additive helps to limit the formation of W₂C phase in sintered WC materials. The pure WC specimen possesses a hardness (HV₁₀) of 25.71 GPa, fracture toughness of 4.54 MPa·m^1/2, and transverse fracture strength of 862 MPa, while those of WC-6.8 vol.% Al₂O₃ composites are 24.48 GPa, 6.01 MPa·m^1/2, and 1245 MPa respectively. The higher fracture toughness and transverse fracture strength of WC-6.8 vol.% Al₂O₃ are thought to result from the reduction of W₂C phase, the crack-bridging by Al₂O₃ particles and the local change in fracture mode from intergranular to transgranular.     

Cold spray of SiC and Al<Subscript>2</Subscript>O<Subscript>3</Subscript> with soft metal incorporation: A technical contribution

Al + SiC, Al + Al₂O₃ composites as well as pure Al, SiC, and Al₂O₃ coatings were prepared on Si substrates by the cold gas dynamic spray process (CGDS or cold spray). The powder composition of metal (Al) and ceramic (SiC, Al₂O₃) was varied into 1:1 and 10:1 wt.%, respectively. The propellant gas was air heated up to 330 °C and the gas pressure was fixed at 0.7 MPa. SiC and Al₂O₃ have been successfully sprayed producing coatings with more than 50 μm in thickness with the incorporation of Al as a binder. Also, hard ceramic particles showed peening effects on the coating surfaces. In the case of pure Al metal coating, there was no crater formation on hard Si substrates. However, when Al mixed with SiC and Al₂O₃, craters were observed and their quantities and sizes depended on the composition, aggregation and size of raw materials.     

Preparation and properties of sintered molybdenum doped with La2O3/MoSi2

Sintered Mo with the addition of La₂O₃/MoSi₂ was prepared via the process of solid–solid doping + powder metallurgy. X-ray diffraction experiment, hardness test, three-point bending test and high-temperature tensile test were carried out to characterize the samples. The XRD pattern of a typical sample shows that the sintered Mo was mainly composed of Mo, La₂O₃ and Mo₅Si₃. Mo₅Si₃ was probably formed through the reaction between MoSi₂ and the Mo matrix. Densities and fracture toughnesses of both doped Mo and pure Mo were measured and contrasted. Sintered Mo with the addition of 0.2 wt% La₂O₃/MoSi₂ has the highest toughness, while more addition of La₂O₃/MoSi₂ has smaller effect on improving toughness or even embrittles Mo. The results of three-point bending test and high-temperature tensile test show that the bending strength and high-temperature tensile strength of doped Mo are both higher than those of pure Mo. The formation of Mo₅Si₃ improves the high-temperature strength. The La₂O₃/Mo₅Si₃ dispersed in the Mo matrix refined the grains, and thus strengthened the Mo matrix by dispersion strengthening and grain refinement.     

Preparation, microstructure and properties of molybdenum alloys reinforced by in-situ Al2O3 particles

The conventional molybdenum alloys, lacking of hard particles enhancing wear property, have relative poor wear resistance though they are widely used in wear parts. To resolve the above question, Mo alloys reinforced by in-situ Al₂O₃ particles are developed using powder metallurgy method. The in-situ α-Al₂O₃ particles in molybdenum matrix are obtained by the decomposition of aluminum nitrate after liquid-solid incorporation of MoO₂ and Al(NO₃)₃ aqueous solution. The α-Al₂O₃ particles well bonded with molybdenum distribute evenly in matrix of Mo alloys, which refine grains of alloys and increase hardness of alloys. The absolute density of alloy increases firstly and then decreases with the increase of Al₂O₃ content, while the relative density rises continuously. The friction coefficient of alloy, fluctuating around 0.5, is slightly influenced by Al₂O₃. However, the wear resistance of alloy obviously affected by the Al₂O₃ particles rises remarkably with the increasing of Al₂O₃ content. The Al₂O₃ particles can efficiently resist micro-cutting to protect molybdenum matrix, and therefore enhances the wear resistance of Mo alloy.     

Fabrication of A356 composite reinforced with micro and nano Al2O3 particles by a developed compocasting method and study of its properties

Aluminum/alumina composites are used in automotive and aerospace industries due to their low density and good mechanical strength. In this study, compocasting was used to fabricate aluminum-matrix composite reinforced with micro and nano-alumina particles. Different weight fractions of micro (3, 5 and 7.5 wt.%) and nano (1, 2, 3 and 4 wt.%) alumina particles were injected by argon gas into the semi-solid state A356 aluminum alloy and stirred by a mechanical stirrer with different speeds of 200, 300 and 450 rpm. The microstructure of the composite samples was investigated by Optical and Scanning Electron Microscopy. Also, density and hardness variation of micro and nano composites were measured. The microstructure study results revealed that application of compocasting process led to a transformation of a dendritic to a nondendritic structure of the matrix alloy. The SEM micrographs revealed that Al₂O₃ nano particles were surrounded by silicon eutectic and inclined to move toward inter-dendritic regions. They were dispersed uniformly in the matrix when 1, 2 and 3 wt.% nano Al₂O₃ or 3 and 5 wt.% micro Al₂O₃ was added, while, further increase in Al₂O₃ (4 wt.% nano Al₂O₃ and 7.5 wt.% micro Al₂O₃) led to agglomeration. The density measurements showed that the amount of porosity in the composites increased with increasing weight fraction and speed of stirring and decreasing particle size. The hardness results indicated that the hardness of the composites increased with decreasing size and increasing weight fraction of particles.