液相烧结对微-纳复合ZTA陶瓷组织性能的影响

在微-纳复合ZTA材料中加入少量复合助剂，材料在较低温度下实现液相烧结，促进了材料的致密化过程，提高了材料的相对密度。ZTA陶瓷发生液相烧结后，ZrO2在晶界处所形成的熔与未熔共存的独特微观结构使之在基体晶界上分布更加均匀，晶界结合较为紧密，钉扎作用增强，材料得到了强韧化。由于ZrO2与Al2O3的弹性模量不匹配，在粒子周围形成的切应力使扩展裂纹遇到未溶粒子易发生偏折，造成部分的穿晶断裂，使材料的断裂模式发生改变。并且这种结构更加有利于应力诱导相变。能够有效地提高材料的力学性能。     

ZTA15铸造钛合金高周疲劳性能研究

目的 研究ZTA15铸造钛合金的高周疲劳性能及其疲劳断裂微观机理。方法 测试ZTA15铸造钛合金的室温轴向拉伸高周疲劳性能,并对合金的金相组织和断口形貌进行观察与分析。结果 随着应力比的提高,ZTA15铸造钛合金的疲劳强度相应提高,疲劳寿命也相应延长。应力比为-1、0.06、0.5时,相应ZTA15铸造钛合金的中值疲劳强度分别为341.5、512.5、643 MPa。疲劳断口形貌显示,疲劳裂纹多萌生于试棒的表面和次表面,裂纹萌生区呈类解理断裂特征。裂纹扩展区可以观察到明显的疲劳辉纹、扩展台阶和二次裂纹等典型特征。结论 疲劳失效机理和疲劳性能差异与合金的显微组织有一定的关系。应力比对疲劳性能的影响主要作用于疲劳裂纹的萌生和扩展阶段。     

Surface synthesis of aluminum borate whiskers on the ZTA ceramics and its application to joining

In this study, aluminum borate whiskers were prepared on the zirconia-toughened alumina (ZTA) substrates for the first time. This result was achieved by calcining a mixture of B₂O₃ powders with and without adding the MnO₂ flux in air. The morphologies of as-prepared whiskers were carefully characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The length-diameter ratio of whiskers prepared by adding MnO₂ flux is larger than those prepared by using only B₂O₃ powders, and the growth mechanisms of whiskers follow solid–liquid–solid theory. In addition, aluminum borate whiskers were successfully used to join ZTA ceramics. By adding the MnO₂ flux in the interlayer, the strength of the joints can be significantly improved. The highest flexural strength for the ZTA/whiskers/ZTA joints bonded using B₂O₃ + 5 wt% MnO₂ powders reached 162 ± 11 MPa at 1100 °C after holding for 4 h.     

高强韧陶瓷的冲蚀磨损行为

本文研究了在室温、320℃、500℃等三种温度下两类陶瓷(氧化锆增韧氧化铝陶瓷,ZTA,与四方氧化锆多晶陶瓷,TZP)的冲蚀性能。ZTA陶瓷的耐冲蚀性显示出较好的温度稳定性。 SEM研究表明,具有高K_(10)的TZP陶瓷的冲蚀磨损主要由塑性变形和径向裂纹构成;ZTA陶瓷因硬度高与K_(10)值低,其冲蚀磨损主要表现为横向裂纹所引起的表面断裂。实验证明,没有常规机械性能与上述两类陶瓷的冲蚀磨损行为直接有关。     

t-ZrO2 toughened Al2O3 free-standing films and as oxidation mitigating thin films on silicon nitride via colloidal processing of flame made nanopowders (NPs)

Zirconia toughened aluminas (ZTAs) are one of the most important engineering ceramics with high melting points, excellent mechanical strength, and chemical stability, and are commonly used as wear resistant and high-temperature components, as prosthetic implants, and electric circuit substrates. In this work, we explore methods of processing fine-grained, dense, thin, free-standing (ZrO₂)_x(Al₂O₃)_1−x films (x = 0-50 mol%, ~40 μm thick) by sintering flame made nanopowders (NPs) to optimize the t-ZrO₂ content, sinterability, and microstructures under select conditions (1120°C-1500°C/5 h in O₂ or 95%N₂/5%H₂). In all cases, the final sintered products retain t-ZrO₂ with average grain sizes (AGSs) of 0.1-1 μm. ZTA film thicknesses were increased to ~200 μm to assess potential as electronic substrates. Excellent fracture toughness (24 MPa m^1/2) and small AGSs of 0.7 μm were found for ~200 μm thick ZTA films sintered at 1500°C/5 h/N₂/H₂ using a three-step binder burnout process. Furthermore, we show that homogeneous ZTA thin films (<5 μm thick) can be sintered on Si₃N₄ substrates (thickness ≈ 300 μm) to provide physical protection against oxidation under extreme conditions (1500°C/1 h/O₂), offering additional practical utility for high-temperature ceramics and power electronic substrates.     

Effect of TZP nanoparticles synthesized by RCVD on mechanical properties of ZTA composites sintered by SPS

Alumina is an engineering ceramic material with excellent comprehensive properties as well as the inherent shortcoming of the low fracture toughness. Y₂O₃-stabilized t-ZrO₂ (TZP) is an effective additive to improve its fracture toughness. In this work, rotary chemical vapor deposition (RCVD) was applied to uniformly coat TZP nanoparticles on α-Al₂O₃ powder, and then the powder was compacted via spark plasma sintering. The content of TZP increased from 0.56 to 4.7 wt% with increasing the deposition temperature from 500 to 800 °C but decreased at 900 °C. The RCVD-TZP nanoparticles homogeneously surrounded the α-Al₂O₃ grains and inhibited its growth after sintering. The relative density, fracture toughness and hardness of the ZTA composites had the maximum values of 99.2%, 7.28 ± 0.33 MPa m^1/2, and 19.5 ± 0.5 GPa at 1500 °C and 4.7 wt% RCVD-TZP, respectively, much higher than the ZTA composites directly mixed with TZP commercial powder.     

晶须增强Ag-18Cu复合钎料钎焊氧化锆增韧氧化铝陶瓷接头组织试验研究

采用硼酸铝晶须增强的Ag-18Cu复合钎料对氧化锆增韧氧化铝陶瓷进行钎焊,根据钎料润湿和铺展性能的变化得出合理的晶须加入量。通过扫描电镜进行钎焊接头组织形貌观察,并通过能谱仪进行元素分析,研究钎焊接头微观结构及晶须对接头的强化机理。在改变焊接温度、焊接时间等工艺参数的情况下,进行多次钎焊试验。通过微机控制电子万能试验机及专用夹具,对钎焊后的试验件进行抗剪强度测试。通过测试得到工艺参数对钎焊接头组织及力学性能的影响规律,进而得出最优的工艺参数。     

微波烧结和常压烧结对Al2O3-ZrO2陶瓷磨损行为的影响

采用多模微波烧结系统和常压烧结,对Ａｌ_２Ｏ_３－ＺｒＯ_２复合材料的基本性能进行了研究,提出了相关的磨损机理．与常压烧结相比,微波烧结可以提高ＺＴＡ陶瓷的密度、强度和韧性,使其结构均匀,耐磨性提高．常压烧结样品的磨损主要是晶粒铲平、磨屑填充体内气孔形成光滑的磨损界面;而微波烧结ＺＴＡ陶瓷主要是界面晶粒剥离脱落磨损．载荷的增加使磨损量增大．     

微波烧结ZTA陶瓷的影响因素

通过改进混合加热模式,实现了ZTA陶瓷微波烧结。材料的类型及配比直接影响微波烧结的升温速率;输入功率的提高有助于提高烧结速率;辅助加热体的老化现象降低微波烧结速率;微波烧结过程中应避免出现热剧变现象。