Al2O3/AlTiC/ZrO2/透辉石陶瓷材料的力学性能及微观结构

将金属Al、Al3Ti和TiC以AlTiC中间合金的形式以及ZrO2颗粒共同引入Al2O3基体材料中,热压制备了Al2O3/TiC/ZrO2/AlN复合材料.在此基础上,添加(体积分数)1%透辉石作为烧结助剂,以实现复合材料的液相烧结并促进其致密化程度.复合材料在烧结过程中有新相AlN生成;同时Al、TiC以及Al3Ti释放的Ti原子发生原子重组生成Al2Ti4C.对热压后材料的硬度、断裂韧度和抗弯强度进行了测试和分析;探讨了透辉石对材料致密化程度及力学性能的影响效果;研究了复合材料断面断裂方式的变化对其力学性能的影响;并对AlTiC中间合金的细化特性进行了分析.     

工艺参数对Fe3Al/Al2O3复合材料力学性能的影响研究

以自制的亚微米Fe3Al为增强相、Al2O3为基体相,通过常压烧结制备出Fe3Al/Al2O3复合材料,研究了Fe3Al含量、烧结温度及保温时间对复合材料力学性能的影响.结果表明:增加Fe3Al含量、提高烧结温度及延长保温时间都可以不同程度的提高复合材料力学性能.最佳工艺参数为:Fe3Al含量(质量分数)为15%,成形压力为2488MPa,烧结温度为1380℃.此条件下制备的复合材料的各项力学性能较好:相对密度为93%,维氏硬度为9.3GPa,断裂韧度为7.51MPa·m1/2.烧结温度对提高复合材料力学性能的影响较大.     

制备工艺对B4C/TiC/Mo陶瓷复合材料力学性能的影响

采用热压法制备了10%(质量分数)TiC/4.7%(质量分数)Mo增强B4C基陶瓷,分析了烧结温度、保温时间和烧结压力对力学性能的影响.烧结温度由1 800℃提高到1 900℃时,复合材料的抗弯强度由590MPa提高到705MPa;当烧结温度升至1 950℃,强度反而下降;硬度和韧度随烧结温度升高而提高.在烧结温度为1 900℃压力为35MPa保温时间由15min提高到45min时,抗弯强度由600MPa提高到705MPa;进一步增加保温时间,抗弯强度随保温时间的增加而下降;硬度和韧度随保温时间延长而提高.烧结压力对复合材料力学性能的影响较小.当烧结参数为1 900℃、45min、35MPa,B4C/TiC/Mo陶瓷复合材料抗弯强度、硬度、断裂韧度、相对密度分别为705MPa、20.6GPa、3.82MPa·m1/2、98.2%.     

热压反应合成Al_2O_3-Ho_2O_3/TiAl复合材料

利用Al-Ti-TiO2-Ho2O3体系原位反应合成了Ho掺杂Al2O3/TiAl复合材料。采用DTA结合XRD分析对体系反应过程进行了探讨。借助XRD、EDS和SEM等手段,对放热体系的物相组成及晶粒微观形貌进行了分析表征。结果表明:Al-Ti-TiO2-Ho2O3系原位合成的Al2O3/TiAl复合材料由TiAl、Ti3Al、Al2O3以及HoAl3相组成;Ho2O3的引入对基体相生成比例(TiAl:Ti3Al)有一定的调控作用,并使得基体晶粒和Al2O3晶粒均有所细化且逐渐分布均匀。力学性能测试表明:当Ho2O3的引入量为6%时,材料的抗弯强度达到最大值,约为593.5MPa;断裂韧度达到最大值,为8.74MPa.m1/2,具有可接受的力学性能。     

工艺因素对B4C-AlB12-Al复合材料力学性能的影响

采用粉末冶金法,以B粉、Al粉、B4C粉为原料,在高纯氩气保护条件下,烧结制备了B4C-AlB12-Al复合材料.利用XRD和SEM对其物相组成和显微结构进行表征,研究了初始原料中Al加入量、烧结时间、烧结温度对材料力学性能的影响.结果表明:烧结试样中除含有B4C,AlB12,Al外,还含有Al3BC和少量Al2O3相;升高温度和延长烧结时间均不利于提高材料的抗弯强度;随原料中Al加入量的增加,材料的力学性能先增加后降低,原料中Al加入量(质量分数)为39.71%时试样的硬度最高为661.43 MPa,Al加入量为45.85%时抗弯强度最高达64.15 MPa.     

透辉石/AlTiB增韧补强氧化铝基陶瓷材料烧结动力学和烧结机制

研究了透辉石/AlTiB增韧补强Al2O3基陶瓷材料的无压烧结致密化过程,通过绘制lg(ΔL/L0)-lgt图,用最小二乘法计算了透辉石/AlTiB增韧补强Al2O3基陶瓷材料的表观激活能.计算结果表明:纯Al2O3致密化机制为扩散机制控制;透辉石/AlTiB增韧补强Al2O3基陶瓷材料在烧结初期的致密化机制为液相流动和颗粒重排,在中、后期致密化机制转为扩散机制控制.根据烧结温度和保温时间对复合材料线收缩率的影响,建立了透辉石/AlTiB增韧补强Al2O3基陶瓷材料的烧结动力学方程;纯Al2O3陶瓷材料的烧结特征指数n约为2.5,其烧结过程中的物质迁移机制由体扩散控制;透辉石/AlTiB增韧补强Al2O3基陶瓷材料的烧结特征指数n值介于2.5与3.0之间,其在烧结中、后期的物质迁移机制既有体扩散,也有晶界扩散.     

无压浸渗制备SiC_p/Al复合材料的力学性能研究

采用无压浸渗法制备出不同SiC粒度组成和硅含量的SiCp/Al复合材料,并对其性能进行测试分析。研究结果表明:SiCp/Al-7Si复合材料硬度比SiCp/Al-12Si复合材料的低,但抗弯强度和断裂韧性比SiCp/Al-12Si复合材料的高,对不同SiCp/Al复合材料的力学性能的影响程度各不相同;粒径小的SiC颗粒有利于SiCp/Al复合材料的硬度、抗弯强度和断裂韧性的提高。当SiC粒度为W7,铝合金中Si含量(质量分数)为7%时,SiCp/Al复合材料的抗弯强度为502MPa、断裂韧性为7.1MPa·m1/2、硬度为66HRA。     

HfN含量对ZrB2基陶瓷材料微观组织和力学性能的影响

以HfN为增强剂、Ni为金属添加剂, 通过真空热压烧结工艺制备了ZrB₂-HfN陶瓷材料, 研究了HfN含量(质量分数)对ZrB₂基陶瓷材料微观组织和力学性能的影响。结果表明: 随着HfN质量分数从5%增加到15%, ZrB₂-HfN陶瓷材料的硬度和抗弯强度先增大后减小, 而断裂韧度逐渐增大; 当HfN质量分数为15%时, ZrB₂-HfN陶瓷材料的断裂模式为穿晶断裂与沿晶断裂共存; 当HfN含量为10%时, ZrB₂-HfN陶瓷材料具有较好的综合力学性能, 其硬度、抗弯强度和断裂韧度分别为: (16.47±0.24) GPa、(734.48±25) MPa和(5.37±0.20) MPa·m 1/2。     

添加剂CeO2对WC-Al2O3复合材料微观组织和力学性能的影响

为了进一步提高WC-Al2O3复合材料的力学性能,研究少量添加剂CeO2对热压烧结WC-Al2O3复合材料的影响。研究结果表明,在WC-Al2O3复合材料中添加0.1%CeO2后,与不含添加剂相比,组织细化且力学性能有所提高;少量添加剂CeO2具有抑制WC氧化脱碳、细化晶粒、改善基体WC和第二相Al2O3颗粒之间界面结合状况的作用。WC-Al2O3-0.1%CeO2复合材料的致密度达到98.82%,维氏硬度、断裂韧性和抗弯强度分别达到16.89GPa、9.85MPa·m1/2和1024.05MPa。     

WC-Al2O3复合材料热压烧结工艺的改进

材料致密度的高低和晶粒的大小直接影响材料的力学性能和使用性能。为了进一步提高WC-Al2O3复合材料的致密度和控制晶粒尺寸,利用改进的普通热压烧结工艺,即二阶段热压烧结工艺对WC-Al2O3复合材料进行烧结,研究确定最佳二阶段烧结工艺及其对复合材料微观组织和力学性能的影响。结果表明,WC-Al2O3复合材料的最佳二阶段热压烧结工艺为TSS3,即T1=1 600℃,T2=1 450℃,t2=6 h。在TSS3烧结制度下制备的WC-Al2O3复合材料,其致密度(TD)为99%,WC晶粒尺寸为2.38μm,维氏硬度为19.71 GPa,断裂韧性为12 MPa·m1/2,抗弯强度为1 285.03 MPa。与普通热压烧结制度下制备试样的力学性能相比,晶粒尺寸有所减小,致密度、硬度、断裂韧性和抗弯强度均有较明显提高。     

Research on toughening mechanisms of alumina matrix ceramic composite materials improved by rare earth additive

Mixed rare earth elements were incorporated into alumina ceramic materials. Hot-pressing was used to fabricate alumina matrix composites in nitrogen atmosphere protection. Microstructures and mechanical properties of the composites were tested. It was indicated that the bending strength and fracture toughness of alumina matrix ceramic composites sintered at 1550 ℃ and 28 MPa for 30 min were improved evidently. Besides mixed rare earth elements acting as a toughening phase, AlTiC master alloys were also added in as sintering assistants, which could prompt the formation of transient liquid phase, and thus nitrides of rare earth elements were produced. All of the above were beneficial for improving the mechanical properties of alumina matrix ceramic composites.     

Stability of hydroxyapatite while processing short-fibre reinforced hydroxyapatite ceramics

Reinforcement by short fibres has been adapted from modern ceramic processing technologies to achieve an improvement of structural properties of hydroxyapatite. However, the influence of the reinforcement fibres on the thermochemical behaviour of the hydroxyapatite has yet to be clarified comprehensively. Titanium, alumina and 316L-stainless steel, all materials with a proven record as implant materials, were chosen as reinforcement materials. Short fibres of these materials were incorporated in a matrix of hydroxyapatite to toughen the hydroxyapatite. Composites were processed by sintering in air, hot isostatic pressing and a method combining sintering in inert gas atmosphere and hot isostatic pressing.     

Mechanical Behaviors of ZrO2-Al2O3 Ceramic Composites with Y2O3 as Stabilizer

Forlongthebrittlenessofceramicmaterialshasstoodinthewayofindustrialapplicationanddevelop ment.However ,inrecentyears ,suchprogressasthephasetransformationtougheningofzirconia ,thedis persionofparticletougheningandthefiberorwhiskertougheninghavewellimprove…     

Microstructural behaviour of spark plasma sintered composites containing bimodal micro- and nano-sized Al2O3 particles

Spark plasma sintering (SPS) has been recognised, in the recent past, as a very useful method to produce metal matrix composites with enhanced properties if compared with traditional powder metallurgy techniques. Obviously, the materials final properties are strongly related to the reinforcement types and percentages as well as to the processing parameters employed during synthesis. The present paper analyses the effect of microscopic and nanometric alumina particles, blended to pure aluminium in different combinations, on the final properties of metal matrix composites produced via SPS. A strong variation in the microstructural behaviour has been observed by varying the nano to micro alumina particles percentage blended with aluminium ones.     

Mechanical Properties and Friction／Wear Behavior of Copper Alloyed Powder Composites

Copper alloyed powder composites containing nanoparticles were developed by hot pressing. Effects of nanoscale activated sintering aid and fine ceramic particles Al2O3 on hardness, working quality, and behaviors of friction and wear of the composites have been studied, compared with the composites including mieroscale activated sintering aid and microscale ceramic particles. The microstructures of the samples were analyzed by SEM. The resuits show that the materials with nanoscale sintering aid and fine ceramic particles have better mechanical properties and abrasive resistance than the materials with microscale activated sintering aid and microceramic particles. Moreover, element mutual transfer occurs between samples (strip) and abrasive wheel (ring).     

Effect of silver nanoparticles on the microstructure and mechanical properties of alumina ceramics

In this work, the effect of additions of silver nanoparticles on the microstructure and mechanical properties of alumina-based ceramic was studied. The processing method for the manufacturing of alumina/silver composites imply high energy mechanical milling in a planetary type mill, cold uniaxial compaction and pressureless sintering in an inert atmosphere at 1500°C for 2?h. From the results after the milling step, approximately 45% of the powders have a particle size less than 1?μm. The microstructure observed by SEM is very fine and homogenous; the presence of silver apparently inhibits the grain growth of the alumina. With respect to mechanical properties, increases of the silver content in the matrix causes decrease of Young’s modulus and flexural strength of the composite obtained in 1.5 and 4.6%, respectively. On the other hand, the presence of silver greatly enhances the fracture toughness of alumina, from an increase of 4.2?MPa?m^?0.5 for monolithic alumina to 10?MPa?m^?0.5 for alumina with silver additions of 2?wt- %, representing an improvement of 138% in toughness of alumina. Lastly, hardness for this same sample was incremented in 12%.     

SiCp/Fe复合材料电流烧结工艺及性能研究

研究了一种电流加热动态热压烧结工艺,并研制了相应的设备.采用此工艺对颗粒增强铁基复合材料进行了制备研究.比较了普通粉末冶金和此工艺所制备的SiCp/Fe复合材料的性能以及此工艺中模具的不同对材料性能的影响,结合显微组织观察对此工艺的烧结机理进行了讨论.结果表明:采用陶瓷模具进行电流动态热压烧结,对材料性能提高显著,能在短时间内制备出满足实际应用要求的铁基复合材料,材料组织细小均匀.     

Characteristics of hot-pressed fiber-reinforced ceramics with SiC matrix

Silicon carbide ceramics’ matrix composites with SiC or C filaments were fabricated through hot pressing, and the effects of the filament pullout on their fracture toughness were experimentally investigated. The C-rich coating layers on the SiC filaments were found to have a significant effect on the frictional stress at the filament/matrix interfaces, through assising the filamet pullout from the matrix. Although the coating layers were apt to burn out in the sintering process of SiC matrix compposites, a small addition of carbon to the raw materials was found to be effective for the retention of the layers on the fibers, thus increasing the fracture toughness of the composites. The fracture toughness of the C filament/SiC matrix composite increased with temperature due to the larger interfacial frictional stress at higher temperatures, because of the higher thermal expansion of the filament in the radial direction than that of the matrix.