Zr,Yb,Cr对Al-Zn-Mg-Cu合金组织、断裂和局部腐蚀行为的影响

研究复合添加稀土元素Yb和过渡元素Zr,Cr对Al-Zn-Mg-Cu超高强合金组织、强韧性和局部腐蚀(晶间腐蚀和剥落腐蚀)性能的影响。结果表明:单独添加Zr和复合添加Cr,Yb的合金均发生了再结晶现象,合金的强度、韧性和腐蚀抗力均较低。而在Al-Zn-Mg-Cu合金中复合添加Zr,Yb,Cr形成大量10~20 nm、共格的固溶部分Zn,Mg,Cu的(Al,Cr)3(Zr,Yb)弥散相,这些均匀分布于基体的细小共格弥散相能强烈钉扎位错和亚晶界,抑制基体再结晶,使合金亚晶界上的析出相与晶内近似,晶界无沉淀析出带(PFZs,precipitate-free zones)不明显。复合添加Zr,Yb,Cr的Al-Zn-Mg-Cu合金在保持高强度和塑性的同时,沿晶断裂抗力和局部腐蚀抗力显著提高。T6态Al-Zn-Mg-Cu-Zr-Yb-Cr合金的断裂机制主要为韧窝型断裂,剥落腐蚀等级降至EA。再结晶晶界成为超高强Al-Zn-Mg-Cu合金腐蚀和断裂的优先扩展路径。     

复合添加Zr、Cr、Pr对超高强铝合金腐蚀和断裂行为的影响

采用铸锭冶金法制备Al-Zn-Mg-Cu-Zr合金和Al-Zn-Mg-Cu-Zr-Cr-Pr合金。通过金相和扫描电子显微分析以及拉伸性能、极化曲线、晶间腐蚀、剥落腐蚀与应力腐蚀等性能测试,研究复合添加Zr、Cr和Pr对Al-Zn-Mg-Cu合金腐蚀和断裂行为的影响。结果表明,复合添加Zr、Cr和Pr可显著抑制Al-Zn-Mg-Cu合金的再结晶和晶粒长大,从而提高该合金的抗腐蚀能力和力学性能。与单独添加Zr的Al-Zn-Mg-Cu合金相比,复合添加Zr、Cr、Pr的相同合金的断裂韧性KIC从20.22 MPa.m1/2提高到26.83 MPa.m1/2,应力腐蚀开裂界限应力强度因子KISCC由9.8 MPa.m1/2提高到17.6 MPa.m1/2,抗拉强度、屈服强度及伸长率均有所提高。研究还发现,再结晶晶粒的晶界为腐蚀和断裂的优先选择路径,抑制再结晶和晶粒长大至关重要。     

固溶处理对Al-Zn-Mg-Cu合金显微组织的影响

通过光学显微镜(OM)、力学性能检测、电导率测定等分析方法,研究了固溶处理对Al-Zn-Mg-Cu合金显微组织和性能的影响。结果表明:单级固溶温度越高(450℃~500℃),合金固溶程度越大,而再结晶也越严重。与单级固溶处理制度相比,450℃×1h+490℃×1h的双级固溶,120℃×24h时效后,合金综合性能显著提高。     

添加Yb对Al-Zn-Mg-Cu-Zr-Cr合金组织性能的影响

采用熔炼铸造法制备复合添加Zr、Cr及复合添加Zr、Cr和Yb的2种Al-Zn-Mg-Cu合金。采用金相显微镜、透射电镜和扫描电镜观察合金的显微组织,并进行力学性能和抗腐蚀性能测试。结果表明：Al Zn Mg Cu-Zr-Cr-Yb合金经固溶处理后始终保持以小角度晶界为主的纤维状组织,这归因于合金中析出的大量细小(10～20 nm)、弥散分布的(Al,Cr)₃(Zr,Yb)相,阻碍了位错和晶界迁移,明显抑制基体再结晶。由于Yb元素的加入,合金的硬度、强度、伸长率和断裂韧性提高,断裂韧性由24.2 MPa·m^1/2提高到32.4 MPa·m^1/2。同时,合金的抗应力腐蚀、晶间腐蚀和剥落腐蚀性能提高,应力腐蚀开裂临界应力强度因子(K_ISCC)由10.6MPa·m^1/2提高到17.0 MPa·m^1/2,晶间腐蚀深度减小,剥蚀敏感性降低,剥蚀等级由EB+降为EA。     

高强Al-Zn-Mg-Cu合金的固溶处理制度

采用力学性能实验、金相分析以及正交设计实验,研究了单级和多级固溶处理条件对高强Al-Zn-Mg-Cu合金薄板力学性能的影响.结果表明,高强Al-Zn-Mg-Cu合金薄板合适固溶处理温度为470℃,延长固溶处理时间对其横向强度和延伸率不利.250℃×2h 420℃×4h 450℃×3h 470℃×80min的多级固溶处理有提高Al-Zn-Mg-Cu合金薄板强度的作用.470℃最终固溶处理之前的多级预固溶处理有阻碍合金薄板在最终固溶处理时再结晶的作用.     

形变热处理对Cu-0.3Cr-0.1Zr合金上引铸坯杆组织性能的影响

通过对上引Cu-0.3Cr-0.1Zr合金固溶处理、冷拉拔以及随后的时效处理工艺,研究冷拉拔形变及时效对材料力学性能、导电性能及组织结构的影响规律.结果表明:时效前的冷拉拔变形能提高Cu-0.3Cr-0.1Zr合金的力学性能而保持较高的导电率;合金在950℃固溶1 h后,经70%冷拉拔变形和500℃时效4 h,合金抗拉强度和导电率分别达到了418 MPa和87%IACS;时效合金组织转变过程为:固溶体G.P.区Cr+Cu4Zr,析出相对位错运动的阻碍是合金强化的重要机制.     

Al-Zn-Mg-Cu系铝合金微合金化的研究进展

就单一合金元素及复合多种合金元素对Al-Zn-Mg-Cu系铝合金的铸态组织、析出相、力学性能及腐蚀性能的影响进行综述。单独加入稀土元素Er,Ce,Ho,Sc等,可以净化基体,使合金熔铸缺陷明显减少,细化晶粒,促进合金元素在基体中的固溶,使晶界减少偏析;单独加入微量的Zr,可以提高合金的再结晶温度,抗拉强度,应力腐蚀能力;复合添加稀土及其他微量合金元素,对提高铝合金的综合性能更为有效。     

高温固溶处理对Mg-15Gd-2Zn-0.6Zr合金组织结构及力学性能的影响

通过光学显微镜(OM)、X射线衍射仪(XRD)、扫描电镜(SEM)和力学试验,研究了510℃下固溶处理20h所得Mg-15Gd-2Zn-0.6Zr合金的组织结构及力学性能。结果表明,铸态Mg-15Gd-2Zn-0.6Zr合金主要由树枝状α-Mg基体以及分布于枝晶间的(Mg,Zn)_3Gd共晶相组成;固溶处理后,合金相组成未发生变化,而(Mg,Zn)_3Gd相形貌由连续网状转变为不连续岛状,体积分数由19%下降为9%;固溶态合金中未观察到长周期堆垛有序结构的形成。拉伸条件下,固溶态Mg-15Gd-2Zn-0.6Zr合金屈服强度比铸态略有下降,但抗拉强度和延伸率均有较大提高,其屈服强度、抗拉强度和延伸率依次为176 MPa、277 MPa和12.8%,表现出优良的综合力学性能;压缩条件下,铸态和固溶态Mg-15Gd-2Zn-0.6Zr合金的力学性能差异较小,且均优于拉伸条件下的力学性能。     

Cu0.69Cr0.13Zr合金中析出相的纤维化及对性能的影响

文章通过对Cu0.69Cr0.13Zr合金铸锭进行热挤压、固溶、时效处理以及冷拉拔等工艺处理之后,通过对试样的抗拉强度、导电性能进行测试,并对不同工艺处理前后显微组织的变化进行观察对比,研究试样经不同处理工艺后的显微组织变化和抗拉强度及导电性之间的关系。研究发现,经960℃、0.5 h不完全固溶的Cu0.69Cr0.13Zr合金,铸造过程中形成的析出相能够在水封正挤的过程中形成纤维组织,该纤维组织在后续冷加工过程中得到进一步的纤维化和伸长;纤维组织的存在使Cu0.69Cr0.13Zr合金的强度由590MPa提高至690MPa,而导电率由80.0%IACS变为80.3%IACS。     

Zr元素对超高强铝合金微观组织及力学性能的影响

研究了Zr元素对Al-Zn-Mg-Cu系合金微观组织及力学性能的影响。结果表明,合金的强度随着Zr含量的增加而提高,当Zr含量为0.12wt%时,合金的强度和延伸率出现峰值。当Zr含量>0.12wt%时随着Zr含量的增加合金强度降低,这是因为合金中的Zr含量过高时,会析出粗大的Al3Zr初生相,降低了合金凝固时固溶在基体中的Zr含量,从而使Zr的有益作用降低。添加Zr可抑制合金的再结晶,使合金组织细化,提高了合金的抗剥落腐蚀性能。TEM分析发现Zr含量为0.12wt%的铝合金固溶态下Al3Zr颗粒比较细小,且分布比较均匀,Al3Zr的平均直径约为16.6nm。研究结果表明,对于所研究的超高强铝合金,Zr的最佳添加范围为0.10%-0.12wt%。     

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。     

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。     

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.     

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。     

Effect of antibiotics of chemotaxis of human leukocytes

The effect of 20 different antibiotics on chemotaxis by human neutrophils was studied. Human leukocytes incubated with chloramphenicol, rifampin, sodium fusidate, and tetracyclines in vitro showed markedly depressed migration. The mechanisms by which these antibiotics affect leukotaxis are discussed.