Custom 450钢热加工图及显微组织分析

 为了探究Custom 450高强度不锈钢最佳的热变形区间以指导实际生产过程的工艺参数设计,利用Gleeble-3800热模拟试验机在变形温度为900~1 200 ℃、应变速率为0.01～10 s-1的条件下开展了热压缩试验,探讨了Prasad和Murty两种失稳判据在Custom 450钢中的适应性,确定了最佳的热变形区间和塑性失稳机制。研究结果表明,该钢在应变速率为0.2~10 s-1、变形温度为900~1 080 ℃的条件下变形时产生了大量的局部变形带和“项链状”组织,是导致塑性失稳发生的主要原因,显微组织观察结果与Murty准则预测的塑性失稳区更为接近。基于Murty准则建立了Custom 450钢的热加工图,并确定了其最佳的热加工工艺区间分别为1 050~1 200 ℃、0.1~1 s-1和1 100~1 200 ℃、1~10 s-1。     

基于热加工图的中碳钢加工性能分析

以LZ50钢为研究对象,分析了其热压缩应力应变曲线。运用线性回归方法建立了峰值应力应变、临界应力应变、稳态应力应变及材料发生最大软化时应力应变的数学模型。绘制了不同应变下LZ50钢的热加工图以预测锻造过程中组织演变行为,指导生产加工。结果表明,加工硬化率随温度降低或应变速率增加而升高。构建了基于Prasad准则、Murty准则及Poletti准则3种不同失稳判据下的热加工图,通过对比分析得出依据Murty准则的热加工图最适宜预测LZ50钢成形过程中的组织演变。研究发现高温高应变速率区域并没有明显组织缺陷,为"伪失稳区"。最适合LZ50钢锻造的区域为中等温度、中等应变速率区,如1 020℃、0.5s-1,该条件下锻后组织均匀,晶粒呈等轴状。     

15%SiC_p/2009A1复合材料的热变形行为及加工图

为了研发高性能颗粒增强铝基复合材料,采用Gleeble-3800热模拟试验机,研究了粉末冶金15%SiC_p/2009A1复合材料在变形温度为370~520℃、应变速率为0.01~10.00 s-1条件下的高温变形特性。结果表明,当变形速率一定时,该复合材料的流变应力随变形温度升高而降低;当变形温度一定时,复合材料的流变应力随应变速率增大而提高。采用动态材料模型建立了15%SiC_p/2009A1复合材料的热加工图。热加工图表明,在较高应变速率区域(2.00~10.00 s~(-1)),出现流变失稳,有少量颗粒—基体界面开裂和SiC颗粒本身破碎。该复合材料的动态再结晶区域位于加工图的较低应变速率区域(1.00 s~(-1)),功率耗散率值较为适中,为0.24~0.35,此时材料具有良好的塑性,适合进行热加工变形。综合加工图以及微观组织观察结果,获得了复合材料热变形的最佳工艺参数:变形温度为450~490℃、应变速率为0.01~0.10 s~(-1)。     

不同应变及失稳准则Ti-50.9Ni合金加工图研究

根据动态材料模型绘制并分析了不同应变及失稳准则下Ti-50.9%Ni(原子分数)形状记忆合金的加工图。结果表明,应变量对等轴组织Ti-50.9%Ni形状记忆合金加工图的影响较大,Ti-50.9%Ni形状记忆合金热加工的非稳定流动区域随着应变量的增大逐渐由低温高应变速率区域向高温及低应变速率区域扩展。在温度为700~800℃、应变速率约为0.001~0.010 s-1和温度为800~950℃、应变速率约为0.005~0.030 s-1两个区域中,真应变小于0.6时能量耗散效率值η皆大于40%,是适合Ti-50.9%Ni形状记忆合金进行热加工的区域。基于Prasad失稳准则和Murty失稳准则得到的Ti-50.9%Ni形状记忆合金的能量耗散效率等值线分布及塑性失稳区分布相似,且Prasad失稳准则得到的Ti-50.9%Ni形状记忆合金加工失稳区更大一些,而Malas失稳准则确定的Ti-50.9%Ni形状记忆合金进行热加工时的稳定变形区位于中等温度和中等应变速率区域。     

电热合金Cr20 Ni80的热变形行为及热加工图

为了解决Cr20Ni80电热合金锻造开裂的问题,在Gleeb-1500D热模拟试验机上对该合金进行热压缩试验,研究变形温度为900~1220℃,应变速率为0.001~10 s-1条件下的热变形行为,并根据动态材料模型建立合金的热加工图.合金的真应力-真应变曲线呈现稳态流变特征,峰值应力随变形温度的降低或应变速率的升高而增加;热变形过程中稳态流变应力可用双曲正弦本构方程来描述,其激活能为371.29 k J·mol-1.根据热加工图确定了热变形流变失稳区及热变形过程的最佳工艺参数,其加工温度为1050~1200℃,应变速率为0.03~0.08 s-1.优化的热加工工艺在生产中得到验证.     

AZ31镁合金的热变形加工图及其应用

为了确定AZ31镁合金轧制工艺参数,利用Gleeble-3500热模拟试验机进行热压缩试验以测试其热变形行为,并根据动态材料模型理论得到其热加工图.当变形温度为380~400℃、应变速率为3~12 s-1时,功率耗散效率大于30%,属于动态再结晶峰区;在该区域进行异步轧制变形退火处理后得到平均晶粒直径为2.3μm的细晶组织,抗拉强度为322.7 MPa,延伸率为19.6%.当应变速率大于15 s-1时,属于流变失稳区,250~300℃低温加工时合金的塑性显著降低,350~400℃高温加工时合金出现混晶组织.      

Al-Li-Cu-Mg-Zn-Ag合金的热变形特征与加工图研究

采用Gleeble1500热模拟试验机对Al-Li-Cu-Mg-Zn-Ag合金进行等温热压缩实验,研究其在变形温度范围为300~500℃,应变速率范围为0.001~10 s-1内的热变形行为。分析了合金流变曲线特征,构建该合金在真应变分别为0.1,0.3和0.5时的加工图并讨论了真应变为0.5时的安全区和失稳区组织特征。结果表明:Al-Li-Cu-Mg-Zn-Ag合金的流变曲线分为过渡变形阶段和稳态变形阶段,流变应力的数值随变形温度的升高而减小,随应变速率的增加而增大;3种真应变下的加工图显示,能量耗散因子具有相似的变化趋势,均在高温低速区达到峰值,失稳区覆盖的范围随应变量的增加而增大,当真应变为0.5时,失稳区参数为变形温度300~480℃,应变速率0.01~10.00 s-1;当真应变为0.5时,安全区以动态回复组织为主,有少量动态再结晶,失稳区组织出现了局部流变带;在变形量较小(真应变0.5)的情况下,建议Al-Li-Cu-Mg-Zn-Ag合金热加工工艺为变形温度范围410~480℃,应变速率范围0.003~0.100 s~(-1)。     

基于动态材料模型的Ti555211合金热加工图研究

利用Gleeble-3800热模拟实验机,在应变速率在0.001～1.000 s~(-1)以及变形温度在750～950℃范围内对Ti555211合金进行等温恒应变速率压缩实验。基于动态材料模型(DMM)和Prasad失稳准则,建立了Ti555211合金的热加工图,对合金的热加工工艺进行了优化。能量耗散率其极大值出现在(峰值区Ⅰ)应变速率0.001～0.010 s~(-1),变形温度820～850℃和(峰值区Ⅱ)应变速率0.001～0.010 s~(-1),变形温度在约920～950℃。结合微观组织分析,在(α+β)相区加工时,应该选峰值区Ⅰ的加工参数;在β相区加工时,选择峰值区Ⅱ的加工参数。在高应变速率(大于0.4 s~(-1))条件下,易发生变形失稳,主要表现为不均匀变形和加工流线,随着应变的增加,塑形失稳区向低应变速率区扩展,应该避免在此工艺条件下加工。本文通过建立动态材料模型的Ti555211合金的热加工图,从而揭示该材料在两相区和单相区的最佳的加工区和危险区,为该合金的后续产业化提供重要的技术基础。     

T91钢的高温塑性变形及动态再结晶行为

采用Gleeble-1500热模拟试验机进行了T91钢的压缩试验,研究了变形温度为1100~1250℃、应变速率为0.01~1 s-1时该钢的变形行为,分析了流变应力与应变速率和变形温度之间的关系,计算了高温变形时应力指数和变形激活能,并采用Zener-Hollomon参数法构建该钢高温塑性变形的本构关系,绘制了动态再结晶图和热加工图.结果表明:在试验变形条件范围内,其真应力-真应变曲线呈双峰特征;钢中发生了明显的动态再结晶,且再结晶类型属于连续动态再结晶.T91钢的热变形激活能为484 kJ.mol-1,利用加工图确定了热变形的流变失稳区,结合力学性能,可以优先选择的变形温度为1200~1 250℃,应变速率不高于0.1 s-1.      

7055铝合金的热变形行为及挤压工艺研究

采用Gleeble热模拟压缩试验研究了7055铝合金的热变形行为和组织演变规律,获得了变形温度和应变速率理论参数,实现了工业生产验证。结果表明:当温度在380～460℃范围内,应变速率在0.001～0.1s-1间时,合金表现为稳态流变;应变速率为1s-1时,合金发生流变硬化;在此变形参数区间的组织演变以动态回复为主。当变形温度为460℃、应变速率为10s-1时,合金发生严重的塑性失稳。基于热模拟试验与组织分析提出了热变形工艺理论参数,并在工厂进行了挤压验证,最终确定了7055合金较佳的挤压温度为420～440℃,挤压速率为0.3～0.7 m/min。     

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。     

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。     

显微维氏硬度测量不确定度评定

对显微维氏硬度测量不确定度进行评定，建立了不确定度计算的数学模型，确定了影响实验结果的各项因素，计算出了各因素的标准不确定度，得出结果的扩展不确定度，并给出最终测量结果的表达式。     

Concept of freedom of infection of animal flocks

Totally negative results of epidemiological investigation of random samples do not prove the absence of the infection as the pathogen may be restricted to only a few animals in the herd for a long time. The statement "absence of infection" is critical for such situations. The question is raised, whether the statement "absence of infection" should be generally avoided. Classification of herds and flocks according to the prevalence of the pathogen would be more valid for the implementation of control measures.     

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.