Microstructure and Tribological Properties of WC-CeO2/Ni- base Alloy Composite Coatings

运用等离子喷涂技术在7005铝合金表面制备了WC和CeO2颗粒协同增强镍基合金复合涂层,研究了该复合涂层的微观结构和摩擦学性能。结果表明:加入CeO2颗粒细化了复合涂层的显微组织,使WC增强颗粒从圆形变为不规则多边形,并降低了其脱碳分解程度。不同PV值摩擦条件下,WC-CeO2/镍基合金复合涂层的摩擦系数和磨损失重均低于WC/镍基合金复合涂层和镍基合金涂层。PV值小于3.36 N·m/s时,复合涂层磨损表面的最大接触应力低于其弹性极限接触应力,主要发生微观切削磨损和疲劳磨损;PV值大于3.36N·m/s后,磨损表面的最大接触应力超过其弹性极限接触应力,接触温度也急剧上升至648℃,磨损表面出现明显的塑性变形和脱落,其磨损机制变为多次塑变磨损、磨粒磨损和粘着磨损,并伴有氧化磨损。     

Anisotropic elastic properties of thermal spray coatings determined via resonant ultrasound spectroscopy

It is difficult to determine the elastic properties of thermal-sprayed ceramic and metallic coatings owing to the microstructural complexity, sample size and geometry, heterogeneity and availability of suitable techniques. Furthermore, the splat-based build-up of the coating results in transverse anisotropy in the elastic properties. This work reports on such anisotropic elastic properties of these coatings determined by resonant ultrasound spectroscopy. This approach, along with the analysis presented, enables the elastic properties to be determined for the first time as a function of direction and temperature, essential information for design. Coating systems investigated include plasma-sprayed yttria stabilized zirconia and nickel. An additional nickel coating deposited by the high-velocity oxygen-fuel process was also investigated and compared with the plasma-sprayed coating. Average Young’s moduli of the coatings were independently measured by indentation. The elastic properties determined enabled the coating microstructure–elastic property relationships to be described.     

Characterizations on Mechanical Properties and In Vitro Bioactivity of Biomedical Ti–Nb–Zr–CPP Composites Fabricated by Spark Plasma Sintering

To alleviate the bio-inert of Ti alloys as hard tissue implants, Ti–35Nb–7Zr–xCPP(calcium pyrophosphate,x = 5, 10, 15, 20 wt%) composites were prepared by mechanical alloying(MA) and following spark plasma sintering(SPS). Mechanical behaviours and in vitro bioactivity of these composites were investigated systematically. Results showed that the composites consisted of β-Ti matrix, α-Ti, and metal–ceramic phases such as CaO, CaTiO_3, CaZrO_3, and Ti_xP_y. With increasing CPP content, the composites had higher strength(over 1500 MPa) and higher elastic modulus, but suffered almost zero plastic deformation together with lower relative density. When the CPP contents were 5 and 10 wt%,the compressive elastic moduli were 44 and 48 GPa, respectively, which were close to those of natural bones. However, the compressive elastic modulus of the composites increased significantly when CPP contents exceed 10 wt%, thus deteriorating the mechanical compatibility of the composites owing to more α-Ti and metal–ceramic phases. Besides, the surface of Ti–35Nb–7Zr–10CPP composite was deposited as a homogeneous apatite layer during soaking in simulated body fluid(SBF). It indicates a good bioactivity between the implant materials and living bones.     

眼镜框架用316L不锈钢丝性能不均及模压缺陷

对企业生产的眼镜框架用316L不锈钢丝试样的微观组织、表面缺陷及夹杂物进行观察,对试样力学性能进行测试,分析模压前钢丝的头尾部性能异常以及模压后产品的表面缺陷成因。结果表明：钢丝头部试样的抗拉强度在700 MPa左右,规定塑性延伸强度为300 MPa,伸长率接近50%,而尾部试样的抗拉强度达到了900 MPa,规定塑性延伸强度达到700 MPa,伸长率在20%左右。性能差异是由于,退火初期钢丝走线速度较慢,退火过程中提高了走线速度,因而尾部钢丝退火时间较短,同时退火温度变低,使得尾部钢丝的组织内应力未完全消除,导致其强度较高,塑性较差。对模压变形后缺陷钢丝的分析表明：不合格试样的组织分布不均匀,晶粒尺寸达到29.7 μm,合格试样的晶粒尺寸为20.9 μm;不合格试样表面存在暗灰色的夹杂物,EDS分析表明,夹杂物为钙基硅酸盐及硫化物,夹杂物处容易发生点蚀,从而形成凹坑、牙齿印等缺陷。     

汽车发动机用AZ91合金的表面改性层及其性能

对汽车发动机用AZ91合金进行了等离子熔覆表面改性处理,对比分析了Al-Si涂层和Al-Si+Y涂层的显微组织和物相组成,并对改性层的硬度、耐磨性和耐腐蚀性能进行了比较。结果表明,Al-Si熔覆层主要含有α-Mg、Mg17Al12、Mg2Si和Al3Mg2相,Al-Si+Y熔覆层主要含有α-Mg、Mg17Al12、Al3Mg2、Mg2Si和Al2Y相;Al-Si和Al-Si+Y涂层的硬度都高于AZ91合金基体,Y元素的加入形成了细晶强化和弥散强化使得Al-Si+Y涂层具有较高的硬度;汽车发动机表面的耐磨性能从高至低依次为：Al-Si+Y涂层>Al-Si涂层>AZ91合金基材;等离子熔覆改性处理后的发动机缸体的耐腐蚀性能有所提高,其中Al-Si+Y涂层的耐腐蚀性能最好。     

氮含量与终轧温度对车削非调质钢组织性能的影响

研究了氮含量与终轧温度对直接车削用非调质钢组织和性能的影响规律。结果表明,随着氮含量的增加,钢中的铁素体含量逐渐增多,且铁素体组织从晶界向晶内扩展;钢的珠光体团尺寸减少,但幅度较小,而原奥氏体晶粒尺寸先明显减小后增加;氮含量为0.0190%的材料具有最细小的原奥氏体晶粒尺寸和较细的珠光体团尺寸。氮含量为0.0190%、终轧温度为850 ℃时,材料具有最佳的室温综合力学性能,此时,材料的屈服强度640 MPa,抗拉强度915 MPa,伸长率22%,断面收缩率63%,冲击吸收能量82 J。     

催化精馏塔中丁烯—1异构化现象的探讨

本文就甲基叔丁基醚（简称ＭＴＢＥ）／丁烯－１装置催化精馏塔中丁烯－１异构化现象的产生进行阐述,通过对丁烯－１异构化反应进行热力学和动力学分析,找出引起丁烯－１异构化的原因。有针对性地提出解决和防止催化精馏塔内丁烯－１异构化的措施。     

复合添加剂对全粉料制α-A1_2O_3陶瓷抗热震性的影响

本文研究了0．3wt％TiO2和Mgo＋Y2O3＋La2O3复合添加剂对全粉料a-Al2O3抗热震性的影响人试样热震后的抗折强度保持率来看,当复合添加剂含量为0．375wt％及0．5wt％时,不仅可以促进烧结,且由于添加剂有细化晶粒的作用,可使全粉料a-A12O3抗热见性提高。     

Sex Pheromone Components in Defense of Melon Fly, Bactrocera cucurbitae Against Asian House Gecko, Hemidactylus frenatus

The Asian house gecko, Hemidactylus frenatus, after being acclimatized to feeding on the melon fly, Bactrocera cucurbitae, consumed fewer numbers of 15-day-old (DO) and older male melon flies compared to sexually immature flies 10 DO and younger. The first male melon fly that performed mating did so on the 10th day after eclosion (DAE), but >80% of the males performed their first mating between 10 and 15 DAE. This confirmed that between 10 and 15 DAE most male melon flies are already sexually mature and producing sex pheromone. Synthetic 1,3-nonanediol, a component of male melon fly sex pheromone produced endogenously, when topically applied onto the thorax of housefly Musca domestica at ca. 80 or 320 ng/fly, reduced consumption by geckos compared with untreated flies in subsequent days after the first day in a four-day feeding test. Raspberry ketone (RK) is consumed and sequestered into the pheromonal gland and later released as a pheromonal component of male melon fly. Houseflies topically treated with 2.6 g RK/fly did not deter predation by geckos. However, houseflies treated with 5.1 g RK/fly caused geckos to consume fewer flies, especially on the third and fourth days during a four-day feeding test, compared with the period when they were offered untreated flies.     

维生素D2生产新工艺

经预处理、萃取、浓缩、结晶等过程从富含麦角固醇的菌丝体中提取麦角固醇,并用自制紫外光源和反应器将其转化为维生素D_2。此新工艺成本低,麦角固醇转化率高,具有良好的经济效益,得到的麦角固醇和维生素D_2分别符合SIGMA公司试剂标准和国家药典标准。