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1.
预应变对Ni50.2Ti49.8合金记忆特性的影响   总被引:1,自引:0,他引:1  
研究了Ni50.2Ti49.8合金在5种不同预应变(1.96%,3.96%,5.88%,7.85%,9.96%)下的回复应变和逆相变温度;恒定预应变5.88%下,热机械循环对回复应变和逆相变温度的影响。结果表明:预应变使得逆相变温度升高,预应变越大逆相变温度越高。随着预应变的增加回复应变增加,预应变增加到一定程度时回复应变达到最大值,随后回复应变随预应变增加而减少。恒定预应变下热机械循环,随循环次数增加,逆相变温度下降,回复应变减少,随着循环次数进一步增加,逆相变温度和回复应变逐步达到稳定值。  相似文献   

2.
采用极图和取向分布函数方法研究了Ti50Ni49.5Fe0.5形状记忆合金的马氏体相变织构和变体选择规律,比较了热诱发和应力诱发之差异。结果表明,奥氏体主要含有(111)纤维织构和(111)[-1-12]板织构。热诱发的马氏体主要含有(102),(10-2)和(120)系列织构,按照马氏体相变的Bain畸变晶体学唯象理论,分析了所有马氏体孪生变体的织构演变规律,表明热诱发马氏体中12种变体均存在;但应力诱发马氏体相变,变体选择具有择优性,择优规律遵循Schmid定律,即主要是S因子最大和次大的1,2’,3’,4’和2,4变体,但也伴随着微弱的低S因子变体5,6,6’,可能是多晶的催化协同作用,马氏体再取向等原因引起的。  相似文献   

3.
设计了具有形状记忆效应和较强非晶形成能力的(Ti50Ni50-yMy)100-xCux合金,采用悬浮熔炼-水冷铜模吸铸法,通过组元调控制备具有组织连续梯度的形状记忆合金/非晶基复合材料,并研究其组织和力学行为。结果表明:B2-Ti(Ni,Cu)过冷奥氏体相和B19'-Ti(Ni,Cu)热诱发马氏体相析出在铸态非晶基体上,加载断裂应力诱发马氏体相变,马氏体衍射峰比铸态增强且马氏体择优取向。凝固过程的温度梯度决定了复合材料的组织梯度,由表及里,主要为非晶相、马氏体相和奥氏体树枝晶相。加载时形变诱导相变对非晶基体同时增强增韧,复合材料的综合力学性能优异,以连续屈服和强烈的加工硬化为主要特征,(Ti0.5Ni0.48Co0.02)80Cu20断裂强度高达2464 MPa,塑性应变达到13.6%。复合材料断裂表面存在大量密集均匀的脉络纹,析出相周围形成的多重剪切带和玻璃基体上剪切带,扩展方向分别与加载方向呈90°和45°角。  相似文献   

4.
Ti- Ni形状记忆合金 (SMA)具有形状记忆效应和超弹性 ,其特性源于热弹性马氏体的形成和回复过程 ,相变过程的诱发需要温度或载荷变化。SMA要经历多次热应力或外加载荷循环作用 ,疲劳性能非常重要 ,其主要影响因素如下 :(1)合金马氏体相变开始温度 (Ms)。Ms不同导致合金相变过程和内部组织形态不同 ,疲劳寿命也不同。调整 Ni- Ti合金中 Ni含量 ,制备了 Ms 分别为 - 12 0℃ ,- 30℃ ,7.5℃和 70℃的合金。在室温下进行恒应变控制的疲劳试验。S- N曲线表明 :在应变相同的条件下 ,Ms 为 7.5℃的试样疲劳寿命最长 ,- 30℃和 70℃的居中 ,-…  相似文献   

5.
通过示差扫描量热仪(DSC)等试验手段,系统分析了添加稀土元素Ce后所形成的Ti-Ni-Cex(x=2 at%、3 at%、4 at%)系合金的相变行为和形状记忆效应,以及相变温度和相变潜热与稀土含量之间的关系.研究结果表明,相变温度(Ms,Mf,As,Af)受稀土含量的影响较大,总的趋势是先升高后下降,然后有稍微升高;而对相变潜热(马氏体相变潜热ΔHB2M、逆马氏体相变潜热ΔHMB2)的影响,则是随着稀土元素Ce含量的升高呈现上升的趋势;稀土的添加使Ti-Ni二元合金的相变滞后明显变窄,但与稀土的含量没有明显关系.研究发现,添加稀土后Ti-Ni形状记忆合金优良的形状记忆效应没有改变,而相变温度却有明显的提高.  相似文献   

6.
外应力及磁场对粘接Ni52Mn24.4Ga23.6合金马氏体相变的影响   总被引:1,自引:0,他引:1  
真空感应熔炼法制备了多晶Ni52Mn24.4Ga23.6合金,对多晶合金进行了DSC分析和显微组织观察;采用粉末压缩压制的方法制备了粘结Ni52Mn24.4Ga23.6磁体;通过X射线衍射分析,讨论了外应力场和磁场对粘结Ni52Mn24.4Ga23.6磁体马氏体相变的影响。结果表明:外应力能诱发Ni52Mn24.4Ga23.6合金中5M→7M的马氏体间相变,生成具有一定择优取向的7M马氏体;在7M马氏体形核和长大过程中施加磁场,能促使择优生长的7M马氏体变体数增多。  相似文献   

7.
Cu70Zn26Al4合金中存在马氏体转变,高压电镜(1000kV)和分析电镜的观察表明,在室温下的平衡母相为β’相(DO_3型),有部份淬火马氏体、表面马氏体存在,还有少量的γ相。在相变过程内,样品中有微裂纹产生和扩展;在冷却实验中,马氏体以母相的(101)面为基面,新相结构为M12R+2H型,没有择优取向问题。在应力诱发马氏体相变中,马氏体以母相的(110)面为基面,新相结构为M18R,存在择优取向问题。在冷却实验中和应力诱发马氏体相变中,都存在β相的预转变,预马氏体的9R和12H衍射极大。在应力诱发马氏体相变中,预马氏体的出现与否与应力施加的速率有关。  相似文献   

8.
张志方  张春生 《稀有金属》1992,16(6):433-436
利用电阻法和不同温度下的系列拉伸研究了Ni_(47)Ti_(44)Nb_9合金的相变及拉伸变形行为。结果表明:合金的拉伸变形行为强烈地依赖于拉伸变形温度。在Ms点以下,发生马氏体变体的再取向,其临界屈服应力随温度降低出现一极小值,在Ms和M_s~δ温度区间,应力诱发马氏体相变,其临界屈服应力随温度升高而降低。在略高于M_s~δ温度,延伸率出现一极小值,而在M_s~δ和Ms之间延伸率出现一极大值。形变使马氏体的逆相变点显著升高。  相似文献   

9.
对成分(at)为Ti-51.28%Ni合金的相变过程用电阻、金相法进行了研究.发现该合金加热过程中发生M→R+M→B2转变,冷却时则有M→R+M→B2转变.并用电阻-温度曲线测定了不同热处理工艺条件下合金的相变温度,讨论了固溶时效处理制度对马氏体相变及R相变的影响,也讨论了提高合金形状记忆效应稳定性的各种方式,结果表明,“高温固溶,中温时效”是有利于该合金马氏体相变的最佳热处理工艺.也是提高其形状记忆效应的有效途径。  相似文献   

10.
杨卓越  苏杰  陈嘉砚  熊建新 《钢铁》2007,42(5):61-64,78
用X射线衍射技术研究了304奥氏体不锈钢变形诱发马氏体相变倾向对成分的敏感性.在液氮内的拉伸结果表明: C、Mn、Cr和Ni的含量从标准范围的上限降到下限,显著增大形变诱发马氏体相变倾向和形变强化能力,尤其是C、Mn、Cr和Ni的含量接近下限的钢在室温下拉伸形成ε马氏体和α'马氏体,其中α'马氏体快速形成使流变应力迅速上升;此外发现,在液氮温度下,变形早期ε马氏体与α'马氏体同时存在,α'马氏体的体积分数累积到约70%后,ε马氏体消失.  相似文献   

11.
转炉炉壳热应力分析   总被引:5,自引:1,他引:4  
任学平  郭志强  邹家祥 《炼钢》2001,17(6):47-49
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。  相似文献   

12.
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)  相似文献   

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16.
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.  相似文献   

17.
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。  相似文献   

18.
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.  相似文献   

19.
2008年中国电解金属锰发展态势浅析   总被引:1,自引:0,他引:1  
曾湘波 《中国锰业》2008,26(4):27-29
对中国电解金属锰发展的市场态势、价格行情以及原材料供应情况作了初步分析,提出我国电解金属锰行业挑战与机遇并存,只要抓住机遇、迎接挑战、夯实基础、科技创新,电解金属锰行业前景将会更加光明。  相似文献   

20.
Employed 120 male and 113 female undergraduates in a replication of H. L. Mirels's (see record 1970-10386-001) study which found 2 factors in analyzing responses to 23 items on Rotter's Internal-External Control Scale. The same polar dimensions of "luck" as the arbiter of life events as opposed to personal control were found as well as a 2nd dimension of degree of control over political and social institutions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   

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