高性能非均匀结构硬质合金的制备及其形成机理研究

硬质合金作为脆性材料存在韧性与硬度的固有矛盾,生产出硬度和韧性匹配良好的硬质合金,提高硬质合金的性能是当前研究热点之一。研究采用超粗、中、纳米3种不同的WC颗粒粉末,通过适当的球磨工艺及烧结工艺,制备出晶粒呈双尺度的非均匀硬质合金。研究了烧结温度对合金性能的影响,合金制备过程的组织形成机理,合金裂纹扩展的特点及断口形貌特征。结果表明:超粗、中、纳米WC颗粒粉末按照一定的质量比例配比,烧结温度为1 450℃时,制备出的非均匀硬质合金细晶粒均匀地分布于粗晶粒周围,其硬度为1 080 HV30,抗弯强度为2 690 MPa,断裂韧性为25.0 MPa·m1/2,制备的硬质合金材料的综合性能达到最优的平衡。     

添加粗晶WC对WC-Co硬质合金组织与力学性能的影响

以不同粒径WC粉、超细Co粉作为原料,通过低压烧结,制备添加粗晶WC的WC-Co硬质合金。采用XRD,SEM研究WC-Co硬质合金的物相组成及微观形貌,利用维氏硬度仪测试,计算合金的维氏硬度及断裂韧性。结果表明,由于粗晶WC的添加,裂纹在扩展过程中出现了明显的偏转,且穿晶断裂现象明显增多,对裂纹的扩展产生一定的阻力,使硬质合金的韧性提高。当添加的粗晶WC粒径为1μm时,合金的硬度由未添加粗晶WC时的1 930 HV降低至1 800 HV,断裂韧性由12.85 MPa·m1/2提高至15.05 MPa·m1/2,综合力学性能达到最佳平衡。     

双尺度结构WC-6%Co硬质合金球磨工艺研究

以粒度分别为2.4μm和0.9μm的粗细WC和Co为原料,采用常规球磨和真空烧结制备了双尺度结构WC-6%Co硬质合金。利用XRD、SEM观察合金的物相变化及微观组织形貌,并通过对比分析密度、硬度、矫顽磁力、抗弯强度和断裂韧性等研究了球磨工艺对合金综合力学性能的影响。结果表明,随着球磨时间和球料比的增加,WC晶粒逐渐长大,合金的(0001)基面百分比例显著增加,同时■棱柱面比例降低。且相比于球磨时间,增加球料比更能破碎和活化细WC颗粒。预磨24 h、球料比4∶1及混合球磨24 h、球料比2∶1球磨条件下制备的合金综合性能达到最佳,其密度、硬度、矫顽磁力均较优异,抗弯强度最高达到3 250 MPa,同时断裂韧性为11.5 MPa·m~(1/2)。     

WC-Co硬质合金组织结构对断裂韧性和断裂影响的研究

本文研究了钴含量7～30％(体积)、WC晶粒度0.5～3.5μm范围内常规WC-Co硬质合金组织结构对断裂韧性和断裂的影响。采用缺口和裂纹两种试样测定合金的断裂韧性;用体视金相学方法铡定合金的显微组织结构参数,并统计了断裂模式的分布。结果表明:合金的断裂韧性主要取决于钴的含量、分布及钴相平均自由程。根据断裂过程分析,导出裂纹扩展能量释放率与组织结构间的关系式为:G_(IC)=(0.417～0.457)σ_sλ。该类合金脆断的主要微观原因是WC/WC型晶间开裂和WC晶粒穿晶断裂。断口表面,WC/WC型晶间开裂分数与组织结构间的关系为:(F)_(WC/WC)=γ(1-V_(Co))~2/D_(WC)。试验表明,合金的断裂韧性采用缺口试样进行测定是可行的,缺口和裂纹两种试样能量释放率间的关系为:G_(IC(ρ))=G_(IC) 2.1ρ。     

Co对原位合成WC-6Co复合粉末制备 高性能硬质合金的影响

将原位合成的WC-6Co复合粉末添加到300 L、转速50 Hz滚动球磨中湿磨，添加Co粉、晶粒长大抑制剂、石蜡、酒精，湿磨48 h，卸料、过孔径45 μm筛，采用闭式压力喷雾干燥塔制备得到WC-7Co~WC-15Co混合料粉末，对制备混合料粉末形貌、粒度分布、物相、成分进行分析，结果表明:添加Co粉配成WC-Co混合料，当混合料的Co质量分数超过10%，团聚现象明显增强，团聚颗粒明显增大；随着添加Co粉质量分数增加，混合料中氧质量分数增高，松装密度不断减小.将制备得到的WC-7Co~WC-15Co混合料掺成型剂，挤压成型，低压烧结等工序制备超细YG7X~YG15X硬质合金.研究添加不同Co质量分数WC-6Co复合粉末制备YG7X~YG15X超细硬质合金，Co对制备硬质合金的金相组织、形貌、物理力学性能的影响，结果表明:随着添加Co质量分数增加，制备的超细硬质合金硬度、密度不断降低，抗弯强度和断裂韧性先增大、后减小；制备的超细YG7X硬质合金的硬度最高HV₃₀为2 150，抗弯强度最低为3 200 MPa；制备YG10超细硬质合金的抗弯强度最高为4 950 MPa，断裂韧性最高为11.8 MPa·m1/2.      

钴含量对粗晶硬质合金磨损性能的影响

粗晶WC-Co硬质合金作为新型矿用工具材料,在不同工况条件下的耐磨性能与失效行为对其工业应用具有重要影响。本研究以Si C颗粒为磨料,采用MLD-10型动载磨粒磨损试验机,研究钴含量对WC晶粒度为5μm的粗晶硬质合金冲击磨粒磨损性能的影响。实验结果表明:钴的质量分数在6%~14%范围内增加时,硬质合金的磨损系数K均呈线性增加,耐冲击磨粒磨损性能则呈线性降低。粗晶硬质合金的耐冲击磨粒磨损机制为:表面层的钴粘结相先被Si C颗粒磨损,然后合金的耐磨性主要取决于凸出WC颗粒的失效行为。因此,硬质合金的磨损系数K与WC硬质相的体积含量呈正比。     

稀土Y,Ce及其添加方式对硬质合金显微结构与性能的影响

采用在还原碳化法制备WC粉末前添加稀土氧化物Y2O3或CeO2,以及在WC与Co粉末混合球磨时加入该稀土氧化物两种不同的方式,在WC-10Co硬质合金中添加稀土元素,利用金相显微镜和扫描电镜观察稀土硬质合金的组织形貌与显微结构,采用X射线衍射仪(XRD)和电子探针对合金的相成分与微区成分进行分析,并测试合金的硬度、断裂韧性与磁性能,研究稀土及其添加方式对硬质合金结构与性能的影响。结果表明,无论以何种方式添加Y2O3或CeO2,最终制备的硬质合金中稀土元素都与氧共存,并以球形颗粒的形式弥散分布于硬质合金的钴粘结相中。稀土硬质合金中WC晶粒球化趋势明显,WC/WC的邻接度由0.6降低至0.39,断裂韧性由12.8 MPa?m1/2提高至16.7 MPa?m1/2。球形、弥散分布的稀土氧化物颗粒会破坏合金结构的连续性,导致合金强度降低。     

钴粉的粒度对高钴粗颗粒硬质合金性能的影响

本文研究了不同粒度的钴粉对高钴粗颗粒硬质合金性能的影响:选择不同粒度的钴粉,在相同的工艺条件下,制备相同成分的粗颗粒硬质合金,分析检测合金的硬度、磁力、密度、强度,以及金相、定量金相。结果表明:在相同的工艺条件下,随着钴粉粒度的增加,定量金相显示WC粒度逐渐增加,硬度和磁力略有下降,钴粉粒度为2.21μm的合金强度最高。     

不同粘结相WC基硬质合金微观结构与性能

以碳质量分数为理论含碳量的WC为硬质相，在1450℃下通过气压烧结制备WC-20Fe,WC-20Ni和WC-20Co硬质合金，通过X射线衍射、扫描电子显微镜、电子探针和力学性能测试研究了不同金属粘结相对烧结硬质合金微观结构和力学性能的影响。结果表明：WC-20Fe合金出现η脱碳相(Fe₃W₃C),W在粘结相Fe中的溶解度仅有1.915%(质量分数)，WC晶粒尺寸最小。WC-20Ni合金渗碳出现石墨相(C),W在粘结相Ni中的溶解度达到10.753%(质量分数)，WC晶粒尺寸最大，合金硬度最小。WC-20Co合金为正常两相区组织(WC+γ)，具有最高抗弯强度2720 MPa和最大硬度934.41 kg·mm^-2。所有合金断裂模式均为脆性断裂和沿晶断裂，WC-20Co合金断口出现明显的粘结相撕裂。     

Cr3C2含量对热压烧结WC基硬质合金材料微观组织和力学性能的影响

为了研制高强度高硬度的硬质合金刀具材料,本文采用真空热压烧结技术制备Cr₃C₂含量不同的WC基硬质合金。通过XRD、SEM、EDS等分析手段研究其物相组成及微观形貌,探究Cr₃C₂含量对WC基硬质合金力学性能和微观组织的影响规律。结果表明：在WC-Co硬质合金中添加适量Cr₃C₂可有效抑制WC晶粒异常长大,提高晶粒均匀度,减少微观组织缺陷,进而改善其综合力学性能。随Cr₃C₂含量增加,合金的硬度和抗弯强度先升高后降低,断裂韧性先降低后升高。当Cr₃C₂的质量分数为0.4%时,WC基硬质合金综合力学性能最佳,硬度(HV)达到20.97 GPa,抗弯强度为1 584 MPa,断裂韧性为10.92 MPa·m^1/2,其中硬度大幅提高对于硬质合金材料用作切削刀具具有重要意义。     

The effect of amount of possession of the trait of hostility on accuracy of perception of hostility in others.

Some theories of personality hold that an individual's perception of others is influenced by his own personality characteristics; more specifically, that a trait of low social value will be projected more into others, and that insight into the possession of these characteristics reduces this distortion. These 2 hypotheses were tested by having a group of college students rate each other (including themselves) on degree of friendliness or hostility. Agreement with group rating about self yielded the insight score. In general, the hypotheses were supported; the "friendly" Ss were most accurate in their perception of others, and insight was positively associated with accurate perception. From Psyc Abstracts 36:04:4HL16M. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of rates of infection of two methods of emergency ventricular drainage

The rates of infection of two methods of external ventricular drainage in use at Atkinson Morley's Hospital--namely, (a) percutaneous drainage with Rickham reservoirs and (b) tunnelled ventriculostomies--were compared in this retrospective review. Percutaneous drainage of CSF with Rickham reservoirs was associated with a 27% rate of infection as identified by positive microbiological cultures; tunnelled ventriculostomy catheters had a 10% infection rate. The difference in the infection rate between the two methods was statistically significant (P < 0.015). Other variables examined, including the age and sex of the patients and the reasons for ventricular drainage, were not associated with an increased rate of infection. Most infections from either method were caused by a coagulase negative staphylococcus. The average duration of ventricular drainage before identification of positive cultures was 5.7 days for Rickham reservoirs and 6.0 days for ventriculostomies.     

浅析《野草》的版画特征

鲁迅先生一生热爱美术作品,对版画中木刻兴趣尤甚.<野草>作为其"写心之作",亦呈现出一些与木刻版画一致的审美特征:一是具有木刻版画的色彩特征,多对比、多冷色,有阴郁的美感;二是具有木刻版画的力度特征,环境描写、人物刻画处处刀锋毕现,遒劲有力,有一种"力之美".     

四辊破碎机车刀架的改造

针对四辊破碎机车刀架车削中存在的几个问题,详细介绍了电动车刀架的结构和工作原理,建立主要设计参数的数学表达式,并进行适当的分析。改造后,这种电动车刀架运行平稳、可靠、方便、省力,取得了预期的效果。     

转炉炉壳热应力分析

根据实际转炉建立实体模型。以有限元为手段,考虑了炉衬和炉壳材料的物性参数随温度变化的特点和炉衬与炉壳之间膨胀间隙,计算了转炉炉壳在温度载荷和炉衬膨胀压力同时作用下的热应力。所得结果可为转炉炉壳设计提供依据。     

Comparison of the results of surgical and conservative treatment of fractures of the diaphysis of the tibia

In this paper is treated the fundamental problematic of the fracture of the diaphysis of the tibia and the therapeutic results after the conservative and operative treatment are confronted. Among 518 patients with 433 open fractures and 35 with closed fractures of the diaphysis of the tibia, successful treatment of more 2/3 was obtained in the period from 1968 to 1972. Following our casuistics and literature, whose results are similar, we find out that the average total treatment of the osteosynthesis of the fracture of the diaphysis was shortened for 2,5 months depending upon the type and the localisation of the fracture. Apolied methods of the operative and conservative and conservative treatment in relation to the velocity of the medical cure as well as to the extreme anatomical-functional results are analised. We noticed that osteosynthesis, made by the intermedullary nail and the extension of the canals or by a small AO table, by the achieved stability makes conditions of immediate motions and an early rehabilitation. Because of that it gives the best functional results.     

Results of treatment of cancer of the cardia

Cancer of the cardia is traditionally discussed with cardiac cancer of the lower portion of the esophagus and upper gastric cancer invading the esophagus, and the specific characteristics of cancer of the cardia have never been clearly defined. We reviewed the outcome of 172 patients with adenocarcinoma of the cardia who had undergone radical surgery between 1949 and 1994 in the Division of Gastrointestinal Surgery of the Cancer Institute Hospital. The centers of the tumors were located within 2 cm above and below the boundary between the esophagus and the stomach, and their longitudinal diameter was less than 8 cm. We divided the patients into an early period (1949-1979; n = 79) and a late period (1980-1994; n = 93), and focused on the historical transition. There were no differences in patient gender or histology between the two periods. However, the late period was associated with fewer cases of esophageal invasion and shorter longitudinal diameter, as the age of the population advanced. The number of advanced cancers such as the localized and infiltrative type had decreased, and early cancer and early clinical stage had become more common, but despite the fact that the number of early cancers had increased, extended dissection, such as thoracic and paraaortic lymph node dissection, was performed more frequently. By clinical stage, the long-term outcome markedly improved in Stage I patient in the late period, and tended to improve in Stage II and III patients. This appears to have been attributable to the prevention of micrometastasis by extended dissection, although the number of early cancers is another major potential cause. There were no differences in the outcome of Stage IV patients between the two periods, and further advances in multimodality therapy must be awaited. The range of resection is basically proximal gastrectomy, and if there are adequate indications, the prognosis is favorable. In view of the status of lymphatic flow and lymph node metastasis, and long-term results, lateroaortic lymph node dissection is important. Since the number of early cancer patients has been increasing, if intraabdominal recurrence is prevented, intrathoracic lymph node dissection will contribute greatly to the outcome of such patients.     

焦炭热性能指标意义浅析

通过对焦炭在高炉内的历程及其变化规律的剖析,阐述焦炭热性能指标的意义,形象地把焦炭在高炉内的损耗分为三部分(M1,M2,M3)。指出M2对焦比及焦炭价格有一定的指导作用。     

参与式农业基地建设行动方案设计

为了编制实用性强的基地建设行动方案,首先,确定参与式发展的主体,搭建一个"决策框架";其次,针对行动目标,提出不同参与主体,如管理者、农民、消费者等团队与个人的目标及行动内容;最后,工作应向重塑伙伴式合作关系,挖掘农民自我发展潜力,完成三大角色的转换,打造农业基地文化等方向推进.