富氮网状核壳结构Ti-6Al-4V合金组织和力学性能研究

采用放电等离子烧结（SPS）技术将经过高温渗氮处理的Ti-6Al-4V(TC4) 粉末制备成致密的核壳（core shell, CS）结构TC4。并对核壳结构TC4合金在1000 ℃下进行固溶处理，研究了采用不同冷却速度的冷却方式以及不同温度时效处理对核壳结构TC4合金微观组织和力学性能的影响。利用光学显微镜（OM）和扫描电子显微镜（SEM）对核壳结构TC4合金的显微组织和截面形貌进行分析。发现壳层具有接近单一的α相，而核心为α+β相，并且β相连续分布在α相之间，最终形成了这种新颖的核壳结构。在氮的固溶强化和核壳结构的双重作用下，核壳结构TC4合金屈服强度达1180 MPa，断裂延伸率约为10%，力学性能显著提高。通过固溶和时效处理调节壳和核的微观结构，可以进一步提升材料的性能。     

气压烧结Al2O3/TiCN复合材料的研究

运用气压烧结工艺克服了热压工艺的局限性,制备了Al2O3/TiCN复合材料,考察了材料在不同温度烧结时的致密化行为及其力学性能,结果表明气压烧结制备的Al2O3-30wt%TiCN陶瓷复合材料,相对密度达到99.5%,抗折强度为772MPa,硬度为19.6GPa,断裂韧性高达5.82MPa/m2.     

TiN/3Y-TZP复合陶瓷材料的性能及显微结构研究

在3Y-TZP基体中添加平均粒径为2.7μm的TiN颗粒,利用热压烧结方法制备出TiN/3Y-TZP新型复合陶瓷材料,研究了TiN对3Y-TZP的常温力学性能、微观结构及低温抗老化性能的影响.结果表明:TiN和3Y-TZP具有良好的物理和化学相容性;TiN细化了基体材料,对3Y-TZP表现出显著的增韧补强作用,断裂韧性和抗弯强度最高分别达到13.3MPa·m1/2,1410MPa.初步研究了空气中220℃下TiN/3Y-TZP的抗老化性能,证明添加TiN颗粒可明显提高3Y-TZP的抗老化性能.     

碳纳米管-ZrB2-SiC陶瓷基复合材料的制备与性能研究

研究了用热压烧结方法制备的不同碳纳米管(CNTs)含量的ZrB₂-SiC- xwt% CNTs (x=0、1.0、2.5、4.0) 复合材料的工艺条件、力学性能和微观结构. 用TEM观察了试样的微观结构, 用SEM观察了试样断口形貌和裂纹扩展情况, 并对其强韧化机制进行了分析. 研究表明, 碳纳米管主要分布沉积在ZrB2颗粒内部, 形成内晶型结构, 在CNTs含量为2.5%时, 相对密度、维氏硬度和弯曲强度分别为99.6%、21.7GPa和542MPa, 断裂韧性达到6.10MPa·m^1/2. 碳纳米管加入后材料致密性提高、晶粒细化,所形成的内晶型结构是材料强度和韧性得以提高的原因.     

Si3N4／SiC（n）／SiC（w）纳米复合材料力学性能研究

采用热压烧结工艺制备了纳米ＳｉＣ颗粒和ＳｉＣ晶须协同补强增韧的Ｓｉ３Ｎ４基纳米复合陶瓷材料,并对其微观结构和力学性能进行了研究。结果表明：该复合材料室温抗弯强度达１０８０ＭＰａ,断裂韧性Ｋ１ｃ值达１１．７ＭＰａｍ＾１／２。纳米ＳｉＣ颗粒和ＳｉＣ晶须对Ｓｉ３Ｎ４基体具有较好的协同补强增韧作用。     

气压烧结Al2O3/TiCN复合材料的力学性能与显微结构

运用二步气压烧结工艺成功制备了Al2O3-30%(质量分数)TiCN复合材料.材料的相对密度达到99.5%,抗折强度为772MPa,硬度为19.6GPa,断裂韧性高达5.82MPa/m2.该材料的烧结过程为固相烧结,烧结过程中TiCN颗粒几乎没有长大,而Al2O3颗粒则长大为原来3倍左右.材料在冷却过程中由于Al2O3和TiCN的热力学性能的失配而引起的界面微应力增长到50MPa左右,不会在材料中导致晶界开裂,但却足以使晶粒发生位错,从而使材料的性能得以增强.     

核壳式纳米Al2O3/PS复合粒子的表征及增韧选区激光烧结聚苯乙烯的研究

运用TEM,FTIR对乳液聚合方法制备纳米Al2O3/PS复合粒子结构进行了表征,结果表明,制备出的复合粒子具备以纳米氧化铝为核、以聚苯乙烯为壳的核壳式结构;并将核壳式复合粒子用来增韧选区激光烧结聚苯乙烯,结果发现,其缺口冲击强度达到12.1kJ/m2,较纯聚苯乙烯提高了50%左右,比添加未经任何改性处理纳米氧化铝粒子的复合材料提高了30%;利用FE-SEM对试件的冲击断面进行了微观结构分析,结果表明:核壳式纳米Al2O3/PS复合粒子改善了纳米粒子与基体表面极性的差异,增强了其与聚合物基体之间的界面相容性,从而改性了选区激光烧结制备聚苯乙烯基复合材料,并很好地起到增韧的效果.     

LiTaO3颗粒增韧Al2O3陶瓷复合材料的制备与性能

通过冷等胸压成型空气气氛下元压烧结把LiTaO3压电陶瓷颗粒作为增韧相引入Al2O3结构陶瓷，结果发现，LiTaO3与Al2O3在1300℃烧结后能稳定共存，LiTaO3颗粒弥散均匀分布；LiTaO3的加入改善了Al2O3陶瓷的烧结性能；LiTaO3颗粒含量适中的Al2O3基陶瓷复合材料的力学性能显著提高。     

B4C／Al2O3／TiC复合陶瓷的力学性能和微观结构

利用热压烧结工艺成功制备了B4C/Al2O3/TiC复合陶瓷.探讨了TiC含量对B4C/Al2O3/TiC复合陶瓷力学性能和显微结构的影响,并研究了B4C/Al2O3/TiC复合陶瓷的增韧机制.结果表明,在烧结过程中B4C与TiC发生原位反应,生成了TiB2.发生原位反应有效的降低了B4C/Al2O3复合陶瓷的致密化烧结温度;B4C/Al2O3复合陶瓷烧结温度为2150℃,B4C/Al2O3/TiC复合陶瓷的烧结温度为1900℃.而且,原位反应提高了B4C/Al2O3/TiC复合陶瓷相对密度和力学性能.裂纹偏转和裂纹钉扎是B4C/Al2O3/TiC复合材料主要增韧机制.     

Al_2O_3-TiC/TiCN颗粒增强铁基复合材料的研究

利用钛铁矿原位合成的Al2O3-TiC/TiCN-Fe复合粉,通过热压工艺成功制备出了不同比例Al2O3-TiC/TiCN增强的铁基复合材料。研究了Al2O3-TiC/TiCN颗粒对铁基复合材料组织和性能的影响。XRD结果显示,在烧结过程中TiC/TiCN会发生一定程度的氧化,有Ti的中间氧化物出现。制备的Al2O3-TiC/TiCN增强的铁基复合材料的性能比较优良,材料的最高力学性能为抗弯强度1334 MPa,维氏硬度802。     

Effect of nanocrystalline binder on the microstructure and mechanical properties of ultrafine Ti(CN) cermets

The influence of highly deformed nanocrystalline binder ingredient on the overall microstructure and mechanical properties of ultrafine grade Ti(C_0.5N_0.5) cermet was investigated. Nanocrystalline Ni and Ni-aluminides viz. NiAl and Ni₃Al, synthesized by mechanical milling/alloying, were blended to the cermet powder prior to sintering. The mechanically milled nano-Ni contained a mixture of f.c.c. and hexagonal Ni phases. The cermet with nanocrystalline Ni showed a considerably improved microstructure over cermets with commercial coarse grade Ni and exhibits a high Vickers hardness of 16.1 GPa, along with a good fracture toughness value of 9 MPa m^1/2. However, no significant change in the mechanical properties could be detected in the case of nanocrystalline NiAl and Ni₃Al binder addition. The enhanced properties of the cermets containing nano-Ni were attributed to the finer particle size of the hard phase after sintering along with improved particle size distribution caused by rapid dissolution, which prevents excessive coalescence of the hard particles. On the other hand, the presence of high porosity in the cermets containing nano-NiAl and -Ni₃Al apparently nullified any such enhancement.     

The Influence of a Small Boron Addition on the Microstructure and Mechanical Properties of Ti‐6Al‐4V Fabricated by Metal Injection Moulding

The effect of boron additions on the sintering behavior, microstructural development, and mechanical properties of a Ti‐6Al‐4V alloy fabricated by metal injection moulding (MIM) was studied. The addition of boron promotes a significant refinement of the microstructure by changing the microstructure from the typical lamellar to a more equiaxed morphology. The presence of both features: α colonies and α grains were confirmed by electron backscatter diffraction (EBSD) experiments. Furthermore, the pinning effect of TiB particles on grain boundary motion enhances the densification process due to the fact that the separation of pores and grain boundaries is suppressed. As a result of the refinement of the microstructure achieved by adding 0.5 wt% boron to the Ti‐6Al‐4V alloy, excellent tensile (σ_0.2 = 787 MPa, UTS = 902 MPa and ε = 12%) and fatigue (endurance limit = 640 MPa) properties were obtained.     

粉末粒径对热压烧结碳化硼致密化及力学性能的影响

采用平均粒径分别为3.5 μm、1.5 μm和200 nm的碳化硼粉体为原料经1850℃热压烧结制备了碳化硼陶瓷, 研究了粉体粒径对陶瓷烧结致密化过程及其性能的影响。根据保温时间对线收缩率的影响及热压初期的塑性流动机理, 得出了不同粉体间烧结初期的激活能差。结果表明: 在相同工艺条件下, 随着粉体平均粒径的减小, 粉体的扩散激活能降低, 致密化初始温度降低, 而且完成塑性流动所需时间也会明显缩短, 致密化速率加快, 致密度增大; 碳化硼陶瓷的显微结构与力学性能亦随着粉体粒径的减小而改善; 1850℃保温1 h后, 平均粒径为200 nm的粉体制备的碳化硼陶瓷相对密度可达90.5%, 硬度为(17±1.8) GPa。     

原位增韧SiC-YAG复相陶瓷的致密化

以β－ＳｉＣ粉加入少量作为晶种的α－ＳｉＣ为起始原料,通过高温热处理过程中的相变和长柱状晶粒生长来制备原位增韧ＳｉＣ基复相陶瓷;调整埋烧工艺控制高温热处理过程中液相挥发和保持稳定的化学计量比,以保证上全部晶化为ＹＡＧ相,着重解决了长柱状晶粒生长过程中的致密化。发现在完全形成紧密的网络状结构之前,长柱状晶粒的形成可能延缓致密化速率,但不会由此中止致密化过程。通过调整热处理条件,制备得到了完全致密化（     

TiB2/FeMo陶瓷的显微结构与力学性能

以Fe-Mo为助烧剂，通过热压制备了TiB2陶瓷．研究了烧结温度、烧结时间对材料显微结构和力学性能的影响，分析了烧结致密化过程．实验结果表明，随着热压烧结温度升高，材料抗弯强度、洛氏硬度出现峰值，热压烧结时间延长，抗弯强度有所下降．液相烧结的重排阶段致密化速率最快．     

石墨烯/纳米Al2O3增韧Ti(C,N)基金属陶瓷的力学及摩擦磨损性能

采用真空热压烧结工艺制备了石墨烯(GNPs)和纳米Al₂O₃增韧的Ti(C,N)基金属陶瓷复合刀具材料(TAG)。研究了GNPs和纳米Al₂O₃对复合陶瓷材料微观结构、力学性能和摩擦磨损性能的影响。研究表明,GNPs和纳米Al₂O₃的添加对复合陶瓷材料的力学性能有明显的提高,当GNPs和纳米Al₂O₃含量(质量分数)为1%和5%时,复合刀具陶瓷材料(TA5G1)综合力学性能最优,其硬度、抗弯强度和断裂韧性分别为21.50 GPa、810.80 MPa和10.51 MPa·m^1/2。研究了复合刀具材料的摩擦磨损性能和磨损机理,研究结果表明,在TAG复合刀具材料中,TA5G1的摩擦磨损性能最优,其摩擦系数和磨损率分别为0.338和4.921×10^-6 mm³/(N·m),复合刀具材料的主要磨损形式为磨粒磨损和黏着磨损。     

烧结助剂对反应热压烧结B4C基复合材料性能的影响

以微米级B₄C粉体为原料,通过与TiO₂葡萄糖原位反应制备TiB₂颗粒增韧B₄C复合材料。研究了烧结温度和烧结助剂对材料烧结行为及力学性能的影响。在1950℃反应热压下获得了相对密度为97.7%的TiB₂/B₄C复合材料,断裂韧性达到5.3 MPa·m1/2。添加Al₂O₃和Si烧结助剂后,分别在1950℃和1900℃ 获得了接近致密的(TiB_2,Al₂O₃)/B₄C和(TiB_2,SiC)/B₄C复合材料,断裂韧性分别提高到7.09和6.35 MPa·m1/2。显微组织分析表明,增韧作用主要来自残余应力引起的裂纹偏转。     

颗粒整形对碳化硅陶瓷密封材料成型及烧结性能的影响

采用球磨对SiC粉体颗粒进行整形,并借助反应烧结制备SiC陶瓷密封材料,考察了颗粒整形对反应烧结SiC陶瓷成型、烧结性能、显微结构和力学性能的影响规律。结果表明,整形后的SiC颗粒的球形度高,粒径分布更为均匀;整形SiC粉体的振实密度和素坯密度明显提高,烧结体的显微结构更加均匀,主晶相为6H-SiC和Si,分布均匀,残炭很少;颗粒整形明显改善SiC陶瓷的成型性能及力学性能,当压力为15MPa时,整形后的SiC素坯密度为2.08g/cm~3,烧结体密度为3.06g/cm~3,抗弯强度和断裂韧性分别达到456MPa和3.87MPa·m1/2。     

Densification,microstructure, and properties of W-Mo-Cu alloys prepared with nano-sized Cu powders via large electric current sintering

This study rapidly fabricated a novel W-Mo-Cu alloy by large current electric field sintering at a relatively low temperature, and the effects of the powder size of Cu on the densification, microstructure, and properties were comprehensively investigated. The particle size of Cu did not influence the phase type but significantly affected the densification, microstructure, and properties. XRD and TEM results showed that the alloy contained three new phases aside from W, Mo, and Cu phases, i.e., Mo-W ordered phase, Mo-Cu solid solution, and Cu_0.4W_0.6 intermetallic compound. Copper powders with smaller sizes were beneficial to improving the distributional homogeneity of elements and the sintering densification. Therefore, the alloy prepared with 100 nm Cu powders had a denser and more homogeneous microstructure and better comprehensive properties than that prepared with 5 μm Cu powders. Overall, the W-Mo-Cu alloy prepared with 100 nm Cu powders at 980 °C proposed the best comprehensive properties, and its relative density can reach 98% approximately.     

Toughening of calcium hydroxyapatite with silver particles

Calcium hydroxyapatite bioceramic was toughened by preparing composites with silver particles as reinforcements. The composites were fabricated from hydroxyapatite and silver oxide raw powders. The sintering behaviour was investigated using dilatometry. An optimized sintering programme was designed to promote densification and to suppress the decomposition of the hydroxyapatite matrix and the evaporation of silver. High density was achieved on both small cylinder samples and large block samples by pressureless sintering. The density of the composites is over 92.4% theoretical with silver inclusions up to 30 vol%. The strength of the composites is greater than 80 MPa as tested by four-point bending. Silver inclusions improve the toughness consistently, from 0.70 MPa m1/2 for the monolithic hydroxyapatite to 2.45 MPa m1/2 at 30 vol% silver. Studies on the toughening mechanism indicate that crack bridging and subsequent plastic work of silver are mostly responsible for the toughening, whereas crack deflection also makes some contribution.