Deformation Behavior and Formability of Gradient Nano-grained AISI 304 Stainless Steel Processed by Ultrasonic Impact Treatment

The deformation behavior and formability of gradient nano-grained（GNG） AISI 304 stainless steel in uniaxial and biaxial states were investigated by means of tensile test and small punch test（SPT）. The GNG top layer was fabricated on coarse grains（CG） AISI 304 by ultrasonic impact treatment. The results showed that the CG substrate could effectively suppress the strain localization of NC in GNG layer, and an approximate linear relationship existed between the thickness of substrate（h） and uniform true strain before necking（ε_（unif））. Grain growth of NC was observed at the stress state with high Stress triaxiality T, which led to better ductility of GNG/CG 304 in SPT, as well as similar true strain after the onset of necking（ε_（neck）） compared with coarse 304 in tensile test. Ei-values of GNG/CG 304 with different structures were nearly the same at different punch speeds, and good formability of GNG/CG 304 was demonstrated. However, punch speed and microstructure needed to be optimized to avoid much lost of membrane strain region in biaxial stress state.

Surface grain refinement mechanism of SMA490BW steel cross joints by ultrasonic impact treatment

Ultrasonic impact treatment (UIT) is a postweld technique for improving the fatigue strength of welded joints. This technique makes use of ultrasonic vibration to impact and plastically deform a weld toe and can achieve surface grain refinement of the weld toe, which is considered as the main reason for the improvement of fatigue strength. In this paper, the microstructure of the surface of a treated weld toe was observed by metallographic microscopy and transmission electron microscopy (TEM). The results show that UIT could produce severe plastic deformation on the surface layer of the weld toe and the maximum depth of plastic deformation extended to approximately 260 μm beneath the treated surface. Repeated processing could exacerbate the plastic deformation on the surface layer, resulting in finer grains. We can conclude that the surface grain refinement mechanism of SMA490BW welded joints is related to the high density of dislocation tangles and dislocation walls. © 2017, University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg.

Improvement of Surface Mechanical and Tribological Characteristics of L-PBF Processed Commercially Pure Titanium through Ultrasonic Impact Treatment

Multi-pass ultrasonic impact treatment(UIT)was applied to modify the microstructure and improve the mechanical and tribological characteristics at the near-surface region of commercially pure Ti(CP-Ti)specimens produced by the laser powder bed fusion(L-PBF)method.UIT considerably refined the L-PBF process-related acicular martensites(α′-M)and produced a well-homogenized and dense surface microstructure,where the porosity content of 1-,3-,and 5-pass UITed samples was reduced by 43,60,and 67%,respectively.The UITed samples showed an enhancement in their near-surface mechanical properties up to a depth of about 300μm.The nanoindentation results for the 3-pass UITed sample revealed an increase of about 53,45,and 220%in its nanohardness,H/E_(r),and H_(3)/E_(r)^(2)indices,respectively.The stylus profilometry results showed that performing the UIT removed the L-PBF-related features/defects and offered a smooth surface.The roughness average(R_(a))and the skewness(R_(sk))of the 3-pass UITed sample were found to be lower than those of the L-PBFed sample by 95 and 223%,respectively.Applying the UIT also enhanced the material ratio,where the maximum load-bearing capacity(~100%)in as-L-PBFed(as-built)and 3-pass UITed samples was obtained at 60-and 10-µm depths,respectively.The tribological investigations showed that applying the UIT resulted in a significant reduction of wear rate and average coefficient of friction(COF)of CP-Ti.For instance,under the normal pressures of 0.05 and 0.2 MPa,the wear rate and COF of the 3-pass UITed sample were lower than those of the L-PBFed sample by 65 and 58%,and 20 and 17%,respectively.

The Impact of Directly Observed Therapy on Preventive Treatment for Latent Tuberculosis Infection among Students in Dalian, China

Preventive treatment has an essential effect on latent tuberculosis infection(LTBI)[purified protein derivative(PPD)induration≥15 mm].Between2010 and 2013,there were 6 tuberculosis(TB)outbreaks in the universities in Dalian,China.So far,in Dalian,the directly observed therapy(DOT)and

Effect of Heat Treatment on Hardness and Impact Toughness of CuCr Containing RE Alloy

The effect of heat treatment on hardness and impact toughness of CuCr containing rare earth alloy was studied by means of metallographic, XRD, SEM/EDX, TEM and mechanical property test. The results show that the heat treatment can change the hardness of CuCr alloy, and has smaller influence to its impact toughness. The optimum properties of CuCr containing RE alloy could be obtained by aging treatment at 500 ℃ for 2 h. And the causes of the above changes and the function of RE were analyzed.

Impacts of Chromium from Tannery Effluent and Evaluation of Alternative Treatment Options

The paper has focused on the challenges/impacts of tannery effluent and evaluates the alternative treatment options used to treat, recover or recycle chromium from the waste water. The paper was done entirely on secondary data by consulting literature sources including scientific journals, chapters of books, conference report papers and websites. The results of this review paper indicated that chromium is highly toxic and carcinogenic to human beings, animals, plants and the general environment (soil and water sediment). It is found out that chrome is the primary threat when ever tanning industry comes in to practice. Though many treatment options were evaluated to prevent its consequence on the environment, neither of them could achieve to treat or recover chrome 100%. Treatment options are either;inef-ficient, complicated, energy demanding, costly or applicable to a certain parts of the world due to technology or skilled man power demand. Therefore, to tackle this serious challenge stringent environmental regulation with law enforce-ment has to be exercised to use better treatment system which is widely applicable. Polluters must also know the envi-ronmental cost of their industry and treated according to polluter pay or precautionary principles. Moreover, the gen-eral public has to be aware of it and all concerned organizations and governments has to work hand in hand to reach zero discharge level or at least to attain the EPA chrome discharge

Environmental Impacts of Farm Waste Treatment Methods and Perspectives of Valorization by Composting: The Case of the Farm “Sociétéde Provenderies du Cameroun (SPC)” of Foumbot

Waste recovery is an environmental, agronomic and economic asset. The farm “Société de Provenderies du Cameroun” (SPC) processes its wastes by incineration and landfill. During this study, environmental impacts of these two treatment methods were assessed in this farm and a composting experiment was also conducted. For the experiment, chicken carcasses and droppings mixed with wood shavings, straw, incineration ash, egg shells and cattle dung were distributed differently in four experimental composters C1, C2, C3 and C4 with the same starting weight. C1 consisted of the first three waste types, for C2, C3 and C4 a new waste was added in the order they are listed above. The results show that the major impacts associated with the incineration and landfilling of SPC waste are the degradation of the health of workers and surrounding populations, the occurrence of conflicts, and the pollution of the air, soil and groundwater of the site. As far as composting is concerned, the characteristics of three of the four composts obtained are usable as soil fertilisers. Indeed, at the end of the experiment, the pH of the four composters was basic (8), the temperature values were between 24°C and 34°C and the humidity values were between 37% and 41%. However, the last parameter, the C/N ratio, was not satisfactory for C1 (13.42), which eliminated it from mature and ready-to-use composts according to FAO standards. The C/N ratios of C2 (15.71), C3 (16.30), and C4 (18) composters were found to be good for mature and ready-to-use compost.

The Treatment of Gestational Diabetes Mellitus

Pre-pregnancy glucose metabolism is normal, only during pregnancy diabetes known as gestational diabetes mellitus. Currently, the diagnostic criteria for gestational diabetes mellitus are IADPSG criteria (International Association of Diabetes and Pregnancy Study Group), and 75 g oral glucose tolerance test is recommended at 24 - 28 weeks of gestation. Gestational diabetes is associated with many pregnancy complications, such as macrosomia, preterm delivery and increased cesarean section rates, and neonatal complications such as hypoglycemia, hypoxia, and respiratory distress syndrome. Early identification of high-risk groups can be carried out for early prevention and intervention which are conducive to improving mothers and infants perinatal outcome. For the treatment of gestational diabetes, lifestyle interventions, such as improved diet combined with exercise to control blood sugar, are recommended first. For patients with poor blood glucose control, insulin is recommended for blood glucose control, and oral drug use is still controversial.

超声能场在金属增材制造组织性能调控中的应用

针对金属增材制造构件存在微观组织缺陷、残余应力及各向异性等问题,各种组织性能调控技术应运而生。结合近年来超声能场对增材制造组织性能调控的研究工作,详细分析了超声能场在增材制造过程中的“液-固”双重效应,总结了超声能场对增材制造金属材料的显微组织及其表面粗糙度、显微硬度、残余应力、耐腐蚀等性能的影响。研究表明,超声能场使材料内部组织晶粒显著细化、孔隙率降低、耐腐蚀性能提高;同时使增材制造构件显微硬度升高,应力状态向有利于构件性能的残余压应力转变。

La-Ce稀土对Q345D钢夹杂物和冲击性能的影响

通过现场试验,分析了La-Ce稀土处理对Q345D结构钢夹杂物、连铸可浇性和钢种性能的影响。结果表明,RE在Q345D结构钢中的合金收得率为21.5%;与未添加RE的炉次相比,脱硫率提高了37.5%,单位夹杂物密度从80.16个/mm^(2),降低至60.78个/mm^(2);La-Ce稀土处理前钢液中夹杂物主要是MgO-Al_(2)O_(3)-CaO复合夹杂,La-Ce稀土处理对小尺寸(D≤5μm)夹杂物的改性作用较为明显,小尺寸夹杂物改性为(La-Ce-S)和(La-Ce-Al-S-O)稀土类夹杂物;La-Ce稀土处理可以明显降低钢中MnS类夹杂物的纵横比,使MnS类夹杂物在轧制后的形貌更接近椭圆形,而没有长线形,这是Q345D结构钢横向冲击功提高20%的主要原因。

超声冲击处理对S355钢表层组织及力学性能的影响

通过超声冲击处理技术对S355钢表面进行处理,分析不同处理时间对材料显微组织、表层残余应力及拉伸性能的影响规律。结果表明,超声冲击处理能够有效地消减S355钢的残余拉应力,引入残余压应力,且引入的残余压应力随着超声冲击时间的增加而增加,在冲击时间达到10 min时,x轴、y轴的残余应力消除值分别为194.81、200.46 MPa。此外,超声冲击处理能够提升材料的抗拉强度和屈服强度,在冲击时间为10 min时,抗拉强度和屈服强度分别增加了16、13 MPa。经超声冲击处理后,试样表层晶粒得到了细化,且观察到明显的加工硬化层。超声冲击处理后材料内部位错密度增加、晶粒细化是导致残余拉应力转变为残余压应力和拉伸性能提升的本质原因。

新型冷作模具钢9Cr5Mo2V不同热处理下的性能研究

以新型冷作模具钢9Cr5Mo2V为研究对象,通过淬回火温度对硬度的影响规律,选出5种不同的热处理工艺,对比不同工艺下模具钢的横、纵向冲击韧性、抗弯强度和耐磨性能,并与7Cr5Mo2V钢进行对照。结果表明,9Cr5Mo2V钢在1030℃淬火、520℃回火热处理下具有极佳的硬度(63.6 HRC)和耐磨性能(260.16 min/mm3);970℃淬火、520℃回火热处理后,其纵向平均冲击功最高,达62.83 J;经970℃淬火、210℃回火热处理后,9Cr5Mo2V钢具有优良的抗弯性能,纵向抗弯强度为3621.9 MPa。9Cr5Mo2V钢的纵向冲击功和抗弯强度均高于横向的纵向冲击功和抗弯强度。

热轧工艺对S32101经济型双相不锈钢低温冲击韧性的影响

为研究热轧工艺对S32101经济型双相不锈钢低温冲击韧性的影响,设计不同的展宽系数(1.0、1.1、1.4)和压下率(75%、90%)进行热轧试验。在计算热力学相图并分析不同温度组织转变规律的基础上,选择合理的固溶处理工艺,研究热轧工艺对固溶处理后S32101双相不锈钢低温冲击韧性的影响。结果表明:不同热轧工艺下,S32101双相不锈钢低温冲击韧性随展宽系数和压下率的增加而提高;随固溶处理温度的升高和保温时间的延长而降低。随展宽系数和压下率的增加,奥氏体和铁素体条带间距减小并沿轧向分布。减小两相条带间距,提高奥氏体相比例可提高低温冲击韧性。

骨性Ⅱ类伴埋伏牙双期矫正病例1例

骨性Ⅱ类的患者常表现为上颌前牙前突,下颌后缩,开唇露齿,前牙深覆牙合、深覆盖等症状,严重影响颜面美观。本文报道1例一期早期矫治配合二期固定矫治治疗骨性Ⅱ类伴埋伏牙的生长发育期男性患者病例。治疗后骨性Ⅱ类症状明显改善,包括下颌后缩的改善,开唇露齿问题得到解决,面部外观趋向于直面型,同时颞下颌关节未出现明显异常。该病例显示早期矫正对此类患者可以达到良好的治疗效果,可以避免或减少此类患者成年后正颌手术的可能性。

基于超声冲击处理的多晶硅还原炉316L不锈钢焊缝消应力研究

电子级多晶硅生产设备有超洁净要求,使得超声冲击处理(Ultrasonic impact treatment,UIT)方法不适应于该类设备的消应力,因为处理导致的表面深坑、毛刺等缺陷可能挂污、藏水,降低产品纯度。鉴于此,研究UIT后打磨去除表面缺陷对引入的残余压应力的影响。结果表明,UIT能够有效将焊缝残余拉应力转变为压应力,高强度UIT和高覆盖率UIT在引入压应力上可达相近效果,打磨去除表面缺陷对残余压应力的影响不大。

埋伏牙正畸治疗的研究进展

滞留在黏膜或骨组织中的牙齿称为埋伏牙,埋伏牙极易造成错𬌗畸形、邻牙病变,甚至影响患者身心健康,是正畸治疗中的难点。本文讨论了埋伏牙正畸治疗时的关键因素,包括牵引时机、暴露埋伏牙的外科术式、牵引方式以及可能促进埋伏牙移动的方法。此外,还强调了在治疗过程中可能出现的并发症和导致牵引失败的因素,包括根骨黏连、牙髓坏死、牙根外吸收、邻牙高度改变和牙周的不良影响,以及相应的治疗预防措施,希望对临床有一定借鉴意义。

典型金属生产过程的环境影响评价研究进展

随着工业化进程加快,金属资源的关键性已成为我国乃至全球关注的问题,金属资源的大范围应用使其在生产时造成的环境影响越来越严重。为选择对环境影响较小的金属种类及生产方式,针对62种典型金属工业生产过程,对其相关的环境影响评价研究进展进行总结,重点关注黑色金属和有色轻、重金属生产过程的环境影响,并对与碳足迹分析相关的研究进行重点总结评述。重金属在生态毒性、人类健康等毒性影响方面均有较大影响;稀有金属和准金属的相关评价主要集中在Li和V上,且是未来的主要研究方向;贵金属相比其他金属造成的碳排放较为显著。金属生产行业未来需重点考虑金属元素自身性质,依据其不同阶段的污染程度优化生产方式,且聚焦金属生产行业的温室气体排放问题。

电化学技术在废水处理中的应用研究进展

随着国内高质量发展的不断推进,公众对水环境污染治理需求日趋提高,电化学水处理技术凭借其优势已经成为解决水污染问题和水资源危机的重要手段。本文总结概述了电化学在环境保护中的优越性,综述了电化学技术处理环境污染物的基本原理,分析了电化学体系研究进展和存在的问题,同时,基于减少工艺系统能耗、降低成本、尝试与传统工艺联合应用等方面,展望了电化学在环境治理领域的应用前景和发展方向。

18CrNiMo7-6渗碳钢磁场深冷处理工艺研究

风电、高铁等高端齿轮产品工作环境比较复杂、恶劣,对齿面硬度及韧性要求高,一旦发生损伤,维修成本高。针对这一现状,对18CrNiMo7-6渗碳钢设计磁场深冷处理正交试验方案,选择最优工艺组进行洛氏硬度检测,并采用光学显微镜观察其显微组织与晶粒度。与常规热处理结果进行对比,探索磁场深冷处理对18CrNiMo7-6渗碳钢冲击韧性、硬度及微观组织的影响。结果表明,磁场深冷处理后的冲击韧性和硬度均有所提升。最优工艺参数为磁场强度为1 T,且不进行交变处理、深冷温度为-190℃、保冷时间为16 h、降温速率为2℃/min,其冲击韧性比常规热处理提高38.07%,洛氏硬度值提高9.49%。微观组织分析表明,磁场深冷处理能促进试样组织中残余奥氏体转变,并细化晶粒。

分析煤矸石填埋场对环境影响及治理对策

煤炭在电力生产、冶金及化学工业等领域有着重要作用。在煤炭开采和洗选过程中会产生大量的固体废物,其中以煤矸石为主。煤矸石若得不到规范管理,将会对生态环境造成严重污染。目前煤矸石有多种处置利用方式,国内采用较多的是填埋方式,本文将从煤矸石的基本特性谈起,再延伸到煤矸石填埋场的现状,分析煤矸石填埋场对生态环境的影响,最后提出煤矸石填埋场的治理对策。