原位合成WC-6Co复合粉末制备超细YG6硬质合金

将原位合成WC-6Co复合粉末采用干袋式冷等静压压制成型(压制压力1×10~8 Pa、保压时间15 s),将压制好的坯料采用低压烧结炉烧结(烧结温度1360℃、烧结时间40 min、加压5 MPa、保温保压时间20 min),烧结制备超细YG6硬质合金,对合金的形貌、金相组织及物理力学性能进行分析。结果表明:原位合成WC-6Co复合粉末制备的超细YG6硬质合金,晶粒异常长大,WC平均晶粒尺寸为0.8μm,硬度HV_(30)为(21500±100) MPa,较传统超细YG6X硬度高。再将WC-6Co复合粉末采用滚动湿磨、压力式喷雾干燥、掺成型剂、挤压成型、低压烧结等工序制备超细YG6硬质合金,研究不同晶粒长大抑制剂配比、球磨时间、挤压压力、烧结温度对合金性能的影响。结果表明:添加0.3%VC、0.8%Cr_3C_2(质量分数),湿磨48 h,挤压压力24 MPa,烧结温度1340℃,制备的超细YG6硬质合金WC晶粒均匀,无异常长大的WC晶粒,WC平均晶粒度尺寸0.4μm,呈多边形,外形较圆。强度、硬度最高,抗弯强度TRS为(2250±20) MPa、硬度HV30为(22600±100) MPa。断口形貌为沿晶断裂,沿WC与WC晶界断裂或WC与Co晶界断裂。     

一种电子元器件银浆用玻璃粉的研制

不同基体的银浆需要采用不同成分的玻璃粉才能达到合适的性能。采用Bi2O3-SiO2-B2O3体系，研究了Ag2O对Zn2SiO4介质陶瓷附着力的影响。当Bi2O3含量(质量分数)为65%，SiO2含量为15%，B2O3含量为10%，Ag2O含量为5%，Al2O3含量为5%时，制备的银浆附着力≥20N；所得银浆料的印刷性能、方阻、附着力、与焊料的润湿性及耐焊性等各项指标符合要求。     

Microstructure,mechanical and wear properties of aluminum borate whisker reinforced aluminum matrix composites

The microstructural features and the consequent mechanical properties were characterized in aluminium borate whisker (ABOw) (5, 10 and 15 wt.%) reinforced commercially-pure aluminium composites fabricated by conventional powder metallurgy technique. The aluminium powder and the whisker were effectively blended by a semi-powder metallurgy method. The blended powder mixtures were cold compacted and sintered at 600 °C. The sintered composites were characterized for microstructural features by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis. Porosity in the composites with variation in ABOw contents was determined. The effect of variation in content of ABOw on mechanical properties, viz. hardness, bending strength and compressive strength of the composites was evaluated. The dry sliding wear behaviour was evaluated at varying sliding distance at constant loads. Maximum flexural strength of 172 MPa and compressive strength of 324 MPa with improved hardness around HV 40.2 are obtained in composite with 10 wt.% ABOw. Further increase in ABOw content deteriorates the properties. A substantial increase in wear resistance is also observed with 10 wt.% ABOw. The excellent combination of mechanical properties of Al−10wt.%ABOw composites is attributed to good interfacial bonds, less porosity and uniformity in the microstructure.     

锰渣复合蛋壳粉对混凝土力学性能的影响

为解决锰渣和蛋壳对环境造成的污染问题,为实现锰渣和蛋壳资源的回收利用。本文对锰渣和蛋壳粉对混凝土的力学性能的相关影响进行了实验探究。在保证混凝土抗折抗压强度均大于对照组的情况下,实验得出了混凝土中可掺入的锰渣和蛋壳粉的最合适掺量:锰渣复合蛋壳粉掺入时,因养护龄期的不同,蛋壳粉的最佳掺量分别为3%和5%;蛋壳粉掺量为0时,锰渣的最佳掺量为5%,最大掺量为10%。     

预混合工艺对铁基粉末冶金材料组织和烧结性能的影响

通过加入新型润滑剂制得Fe-2Cu-0.8C预混合铁基粉末,并制备了同成分机械混合粉末进行对比试验。对粉末流动性、松装密度以及压制性能进行了测试,并对烧结体的微观组织进行表征。结果表明:制备的预混合粉末流动性和松装密度均优于机械混合粉。当润滑剂加入量为0.6 mass%时,经600 MPa压力下压制所得的生坯密度为7.01 g/cm^3,烧结体密度为7.11 g/cm^3,批量压制时零件质量变化小于0.15%。通过预混合工艺,使得铜和石墨颗粒粘结到铁颗粒表面上,从而达到防止偏析和提高批次稳定性的目的。使用预混合粉末不仅提高了烧结体的尺寸精度和性能,同时可制备出更光洁的零件表面,进行形状复杂零件生产时更能体现出其在稳定性方面的优势。     

High pressure EIGA preparation and 3D printing capability of Ti—6Al—4V powder

Ti—6Al—4V alloy powder was processed by electrode induction melting gas atomization (EIGA) at high gas pressure (5.5–7.0 MPa). The effects of atomizing gas pressure on the powder characteristics and the microstructure, along with the mechanical properties of the as-fabricated block by laser melting deposition (LMD), were investigated. The results indicate that the diameters of powders are distributed in a wide range of sizes from 1 to 400 μm, and the median powder size (d₅₀) decreases with increasing gas pressure. The powders with a size fraction of 100–150 μm obtained at gas pressures of 6.0 and 6.5 MPa have better flowability. The oxygen content is consistent with the change trend of gas pressure within a low range of 0.06%–0.20%. Specimens fabricated by LMD are mainly composed of α+β grains with a fine lamellar Widmanstatten structures and have the ultimate tensile strength (UTS) and yield strength of approximately 1100 and 1000 MPa, respectively. Furthermore, the atomized powders have a favorable 3D printing capability, and the mechanical properties of Ti—6Al—4V alloys manufactured by LMD typically exceed those of their cast or wrought counterparts.     

Micromorphology,pharmacognosy, and bio‐elemental analysis of an important medicinal herb: Verbascum thapsus L.

The present study was conducted on characterization of morpho‐anatomical, phytochemical, and bio‐elemental analysis of root, stem, and leaf of Verbascum thapsus. Morphologically Verbascum is a biennial plant that flowers for a month and a half in mid‐ to late summer. Various organoleptic features of root, leaf, and stem were recorded. Anatomically the T. S of the root, stem, and leaf showed a typical dicot histological differentiation. Leaf possessed anomocytic stomata, crescent shape vascular bundles, and covered with long and stellate type trichomes while, stem contained collateral type of vascular bundles and a well‐developed pith to store phytochemicals responsible for various pharmacological activities. The powder drug study through scanning electron microscopy revealed the presence of various types of tissues. Branched, tree like and stellate trichomes in root and leaf help in absorption and reduce loss of water. These anatomical features are responsible for the survival of the plant as biennial. Four macro elements (Na, K, Ca, and Mg) and seven microelements (Cr, Cu, Fe, Mn, Ni, Zn, and Cd) and their concentrations in ppm were also studied using Atomic Absorption Spectroscopy. Phytochemical screening of methanolic extract showed existence of various secondary metabolites, while mucilage and anthraquinones was not detected. The present study helps to understand the taxonomic identification of the plant based on morpho‐anatomical features and throws the attention of the researchers to carry out the work for developing its various formulations, which can ultimately be beneficial for the human beings as well as animals.     

Activation mechanisms on potassium hydroxide enhanced microstructures development of coke powder

Coke powder is expected to be an excellent raw material to produce activated carbon because of its high carbon content. Potassium hydroxide (KOH), as an effective activation agent, was reported to be effective in activating coke powder. However, the microstructures development in the coke powder and its mechanisms when KOH was applied were still unclear. In this study, effects of KOH on the microstructure activation of coke powder were investigated using the surface area and pore structure analyzer, scanning electron microscope (SEM) and thermogravimetry-differential scanning calorimetry-mass spectrometry (TG-DSC-MS), etc. Results revealed that the addition KOH at its lower ratio (mass ratios of KOH and coke powder in a range of 0.5 and 1) decreased the specific surface area and average lateral sizes, but sharply increased of the specific surface area to 132 m²·g^-1 and 355 m²·g^-1 and decreased of the space size of aromatic crystallites upon the further increase of the KOH addition amounts (ratios of KOH and coke powder in a range of 3 and 7), generating a number of new micropores and mesopores. The mechanisms study implied surface reactions between KOH and aliphatic hydrocarbon side chain and other carbon functional groups of the coke powder to destruct aromatic crystallites in one dimension and broaden pores at lower KOH addition. In the activation process, KOH was decomposed to be more active components, which can be rapidly destruct the aromatic layers in spatial scope to form developed porous carbon structures within coke powder at higher KOH addition.     

宽厚板连铸坯表面裂纹的产生原因及控制

针对近期包钢薄板坯连铸连轧厂宽厚板微合金钢铸坯出现的批量表面裂纹问题,通过考察表面缺陷类型,裂纹形貌特征,结合连铸工艺条件、钢水质量及设备状况,分析了板坯表面裂纹的主要原因,提出了优化振动参数,控制钢水氮含量,提高振动精度,调整保护渣性能以及提高二次冷却水水质等改善铸坯表面缺陷等措施,取得了比较明显的效果,其铸坯表面裂纹得到了有效控制。     

Effect of Build Direction on Fatigue Performance of L-PBF 316L Stainless Steel

The microstructure and fatigue and tensile properties of 316 L stainless steel fabricated via laser powder bed fusion(L-PBF)were investigated.Two 316 L stainless steel specimens with different loading directions which are either perpendicular to or parallel to building direction were prepared by L-PBF process.The results of X-ray diffraction tomography showed that there was no significant difference in morphology and size/distribution of the defects in the HB and VB samples.Since long axis of columnar grains is generally parallel to the build direction,the fatigue crack encounters more grain boundaries in VB samples under cyclic loading,which led to enhanced fatigue resistance of VB samples compared with HB sample.In contrast to HB sample,the VB sample has a higher fatigue strength due to a higher resistance to localized plastic deformation under cyclic loading.The differences in fatigue properties of L-PBF 316 L SS with different build directions were predominantly controlled by solidification microstructures.