碳含量对Fe-15Mn-4.5Si-10Cr-5Ni-C系形状记忆合金性能的影响机制

 为通过调控碳含量获得形状记忆性能优异的铁基形状记忆合金,研究了3种不同碳含量对固溶时效态Fe-15Mn-4.5Si-10Cr-5Ni-C系形状记忆合金微观组织、力学性能及形状记忆效应的影响。结果表明,固溶时效态Fe-15Mn-4.5Si-10Cr-5Ni-(0.05~0.2)C合金的形状记忆效应随碳含量的增加呈现先增后减的趋势。这是由于一方面,随着碳含量的增加,碳原子的间隙固溶强化和第二相碳化物的沉淀析出强化提高奥氏体母相强度,抑制不可逆塑性变形的发生,有利于材料在受力时发生应力诱发奥氏体γ转变为ε马氏体(γ→ε),从而提高形状记忆效应。另一方面,全固溶温度随碳含量的增加而升高。由于全固溶温度的升高,固溶处理后得到的相对粗大的奥氏体晶粒造成奥氏体母相强度的降低。同时,随着碳含量的增加导致ε马氏体相变温度(M_εs)的降低,应力诱发相变过程受到抑制,不利于形状记忆效应。在不同影响机制的相互作用下,碳质量分数为0.091 8%固溶时效态试验合金的形状记忆性能最优。     

NiTi记忆合金相变时的电阻和回复特性

通过电阻、回复特性的同时测定,对近等原子比的NiTi记忆合金的马氏体(M)相交进行了研究。实验得出了三种类型的电阻—温度曲线,分析讨论了它们之间的异同。通过电阻变化的规律性,确认从高温相(B2)到马氏体相变的过程中,经历了一个以高电阻为特征的R相的转变。实验还指出,电阻的反常变化和形状回复的温度范围是一致的。形变回复的主要部份不是发生在马氏体逆转变的起点(A_s),而是发生在转变接近完成的温度(靠近A_f)。初步认为在马氏体逆转变过程中R→B2和M→B2的转变对形变回复起主要作用。     

Cu-Al-Mn形状记忆合金的热循环特性

通过电阻-温度曲线测量、金相组织观察和X射线衍射分析研究了热循环对高M_(?)点Cu-11.9Al-2.5Mn(质量分数,％)形状记忆合金马氏体相变的影响。研究结果显示该合金在热循环过程中相变点下降,但仍有较高的高温稳定性和耐热性。这是由于合金马氏体结构(β=89.6°)与N18R非常接近,抑制了M18R→N18R的转变过程与循环中位错积累共同作用的结果,而两者实质上都与有序度的改变有关。     

Fe-Mn-Si-Cr-Ni合金在γ+α'复相状态下的形状记忆效应

用Ｘ射线衍射和ＴＥＭ方法研究了Ｆｅ－１４Ｍｎ－５Ｓｉ－９Ｃｒ－５Ｎｉ合金的应变诱发γ→ε和γ→α’马氏体相变行为,测试了几种合金为单相奥氏体以及奥氏体加α‘马氏体复相原始组织的形状记忆效应。探讨预应变前原始组织中存在的α’马氏体对形状记忆效应的作用。实验结果证实,这些合金从奥氏体加一定体积分数的α‘马氏体复相组织开始预应变,加热逆相变形状回复后,具有更高的形状回复率。     

TiNi形状记忆合金的力学和电阻特性

本文简要报道了采用新型SMT－1型形状记忆合金特性综合测试仪Ti-50.9at%Ni合金在拉伸变形,形状记忆回复以及约束应力或约束应变条件下的力学和电阻特性进行测试的部分结果,并讨论了其内在物理本质。实验结果表明：拉伸加载过程中的电阻－应变曲线比应力－应变曲线更能揭示应力诱发马氏相变过程;合金形状记忆效应的回复湿度随拉伸应变量的增加而增加;在约束条件下,合金回复应力及它随温度上升的趋势与初始应变量有关,应力约束条件下,马氏体相变所对应量比无外加应力作用时有大幅度增加,本研究也表明：应力,应变,电阻,温度的的同步测量是研究形状记忆合金性能和组织结构变化的简例和有效的工龄。     

FeMnSiNiCr形状记忆合金中的γε相变及其形状记忆效应

本文研究了FeMnSiNiCr形状记忆合金中的γ→ε马氏体相变及其逆转变,以及处理方法对合金形状记忆效应(SME)的影响。发现层错扩展导致其有序重叠是ε马氏体形核的主要机制;孪晶界对ε马氏体的形成有较大贡献,并且易于形成相平行的ε马氏体,不易发生相互交叉。这对于合金的形状恢复极为有利。1000℃固溶处理可产生较多的退火孪晶,因此可使合金获得最佳的形状记忆效应。经过三次形变(?)300℃时效循环训练,可使形状恢复率达100％。     

一种高硅Cr—Ni不锈钢热处理后的显微组织转变

研究了一种铸态σ相强化的高硅Ｃｒ－Ｎｉ不锈钢热处理后的显微组织转变。试验结果表明，在１１５０℃高温固溶状态下钢具有α＋γ双相组织；在固溶后冷却及８００℃附近时效过程中，α相和γ相不稳定，发生３种相变反应，即α→α＋σ、α→γ′＋σ及γ→γ＋σ。长期时效后，通过上述反应，最终形成以γ相为基体的γ＋σ双相组织。根据试验结果分析讨论了该钢的组织不稳定性、由α＋γ双相组织转变成γ＋σ组织的相变过程、σ相的形成及强化机制。     

热处理对添加少量Cr、Fe的Ti-Ni合金组织和力学性能的影响

采用真空熔炼法制备Ti_(45)Ni_(55)Cr_(0.3)和Ti_(45)Ni_(52)Fe_3合金(元素含量为摩尔分数)铸锭,对其进行均匀化处理以及850℃/1 h固溶和水淬后,分别采用3种不同的工艺进行热处理:1)850℃/1 h固溶,2)375℃/1 h时效,3)25%冷轧+375℃/1 h退火,研究热处理工艺对合金的相变特性、力学性能、内耗性能和微观组织的影响。结果表明,Ti_(45)Ni_(55)Cr_(0.3)和Ti_(45)Ni_(52)Fe_3合金的基体均由B2与R相组成;Ti_(45)Ni_(55)Cr_(0.3)合金经过375℃/1 h时效或25%冷轧+375℃/1 h退火处理后,析出Cr3Ni2粒子,时效后抗拉强度为1 385 MPa,时效升温过程的峰值内耗达到0.53;Ti_(45)Ni_(52)Fe_3合金经过25%冷轧+375℃/1 h退火后析出Ti3Ni4相,抗拉强度为770 MPa;与其它热处理工艺的升温过程相比,Ti_(45)Ni_(52)Fe_3合金的时效升温过程峰值内耗最高,达到0.158;降温过程中,Ti_(45)Ni_(55)Cr_(0.3)合金在时效降温过程中发生B2→R→M相变,退火的降温过程中发生B2?R相变,而Ti_(45)Ni_(52)Fe_3合金在退火的降温过程中发生B2→R→M相变。     

冷热循环对Ni─Ti形状记忆合金马氏体相变及形状记忆效应的影响

通过电阻及回复特性的测定,研究了在冷热循环条件下ＮｉＴｉ形状记忆合金记忆效应的稳定性问题。实验结果表明：对不同的ＮｉＴｉ合金固溶处理后,冷热循环对其形状记忆效应均产生影响。但时该合金在再结晶温度下时效处理或退火,冷热循环对其相变温度几乎均不产生影响。同时对产生以上规律的内在机制进行了初步探讨。     

热处理对马氏体不锈钢Fv520（B）力学性能的影响

研究了热处理对马氏体沉淀硬化不锈钢Ｆｖ５２０（Ｂ）：０．０５Ｃ－１４．５Ｃｒ－５．５Ｎｉ－１．８Ｃｕ－１．７Ｍｏ－０．３５Ｎｂ的组织和力学性能的影响。结果得出，经１０５０℃固溶处理＋８５０℃中间处理＋４７０℃时效时Ｆｖ５２０（Ｂ）钢的强度达到极大值，时效温度超过５２０℃时，形成逆转变奥氏体，残余奥氏体量增加，６２０℃达到最大值。     

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.