异步轧制对AZ31镁合金板材组织和性能的影响

对不同轧制温度、道次压下量以及轧制路径等工艺条件下所制备的AZ31镁合金板材的组织和性能进行了研究。结果表明,当温度由623K升到723K时,晶粒发生长大,孪晶消失,板材的抗拉强度由275MPa降到250MPa,伸长率则由14.5%增加到18%;当道次压下量从5%增加到20%时,晶粒逐渐得到细化,板材的抗拉强度由道次压下量为5%时的265MPa增加到20%时的300MPa,伸长率则由18%降到15%;轧制路径的改变,使不同板材中孪晶的数量产生改变,路径A中的孪晶较多,伸长率较低,强度较高,路径D中的孪晶较少,伸长率较高,强度较低。     

等离子体处理对石墨膜表面亲水性的影响

目的通过等离子体处理石墨膜,提高石墨膜表面的亲水性。方法采用不同的工艺条件对石墨膜进行等离子体处理,测试石墨膜的表面接触角。利用扫描电子显微镜和原子力显微镜观察石墨膜处理前后表面形貌的变化,通过X射线光电子能谱分析石墨膜处理前后表面成分的变化。采用万能材料试验机测试镀铜样品的剥离强度,评价铜镀层与石墨膜的结合力。结果采用空气处理气氛时,在气体流量为0.4 L/min、功率为60 W的条件下,处理30 s,石墨膜的接触角从处理前的93.41°降至4.49°;表面均方根粗糙度由952.10pm提高到12.54 nm,最大高低差从10.81 nm升至72.70 nm。由X射线光电子能谱分析可知,石墨膜经等离子体处理后,碳元素的原子数分数由未处理的98.37%下降到83.13%,氧元素的原子数分数由未处理的1.63%升高到16.87%,氧碳含量比则由起初的1.66%升高到20.29%。结论石墨膜经等离子体处理后,表面被刻蚀并且引入含氧极性基团,等离子体处理显著提高了石墨膜表面的亲水性。     

Numerical Simulation of the formation of the Sedimentary Zone of Inclusions in Large Steel Ingots

Abstract

A mushy zone is formed in the lower part of an ingot by the showering of crystallites from the top and by free dendrite arms fused and broken from dendrites growing from the side mould wall. The zone obstructs the floating of inclusions. In addition, inclusions floating to the upper part of the ingot can be carried down to the bottom by natural convective flow and can be trapped by the mushy zone. An equiaxed crystal zone in the bottom of a steel ingot results from free crystals coming from the top and sides and from the local growth of crystals caused by heat transfer. The interval from the beginning of pouring to the time when the velocity of convective flow becomes too low to carry any inclusions larger than those of tolerable size down to the bottom is defined as the critical time. The size of the sedimentary zone of inclusions is then equal to that of the equiaxed crystal zone formed in the critical time. In this paper, a method for determing the critical time is proposed, and numerical simulation of the formation of the bottom equiaxed crystal zone has been carried out. A 27Cr2Mo1V steel ingot of 68 tonnes in weight was studied. From the results of the numerical simulation, the weight ratio of the offcut tail end to the ingot body was 8.11%. This result approximately agreed with the weight ratio of 8.8% obtained in production practice with the same ingot.     

异步轧制对AZ31镁合金板材组织和性能的影响

对不同轧制温度、道次压下量以及轧制路径等工艺条件下所制备的AZ31镁合金板材的组织和性能进行了研究。结果表明．当温度由623K升到723K时，晶粒发生长大，孪晶消失，板材的抗拉强度由275MPa降到250MPa，伸长率则由14．5％增加到18％；当道次压下量从5％增加到20％时，晶粒逐渐得到细化，板材的抗拉强度由道次压下量为5％时的265MPa增加到20％时的300MPa，伸长率则由18％降到15％；轧制路径的改变，使不同板材中孪晶的数量产生改变，路径A中的孪晶较多，伸长率较低，强度较高，路径D中的孪晶较少，伸长率较高．强度较低。     

w（Mn）量对灰铸铁铸造缺陷和性能的影响

检测及分析认为,批量生产的涡轮壳铸件出现的大面积夹渣、皮下气孔问题,是铁液中的w（Mn）量过高所致.参照文献推荐数据进行生产试验结果显示,w（Mn）量均值从1.01％降低到0.64％,抗拉强度均值从329 MPa提升到341 MPa,硬度从219 HB降低到217 HB,品质系数从1.13提升到1.18,而且降低了成本,取得了较大的经济效益.     

脉冲电流频率对预制缺陷TC4钛合金性能的影响

为了研究脉冲电流频率对预制缺陷TC4钛合金组织性能的影响规律,首先采用室温预拉伸制备含孔洞缺陷的TC4试样,然后选取不同频率的脉冲电流对预制缺陷的TC4试样进行通电处理,对比通电前后板材内部的显微孔洞和基体组织的变化情况,并对处理后的试样进行二次室温拉伸获得力学性能参数。结果表明：当脉冲电流频率从0升至140Hz时,TC4内部孔洞体积分数由2.21%下降至0.86%,屈服强度由916.7MPa提高到990.9MPa,抗拉强度由951.2MPa增加至997.5MPa,延伸率提高64.86%;当脉冲电流频率从140Hz提高到160Hz时,内部孔洞体积分数反而增至1.99%,屈服强度和抗拉强度则分别下降到975.1MPa和988.5MPa,延伸率降低了37.70%。显微孔洞体积分数几乎决定了预制缺陷TC4钛合金的力学性能。     

退火温度对Incoloy800合金晶间腐蚀敏感性的影响

用草酸腐刻、双环动电位电化学再活化(DL-EPR)及电化学阻抗谱(EIS)3种方法评价了不同温度(550～800℃)退火处理4 h后Incoloy800合金的晶间腐蚀敏感性,研究了退火温度对Incoloy800合金晶间腐蚀敏感性的影响。分别用光学显微镜(OPM)和扫描电子显微镜(SEM)观察了敏化样品经草酸腐刻后的微观结构和DL-EPR测试后的表面形貌。结果表明3种方法评价结果一致,随着退火温度升高,Incoloy800合金的敏化度先增大后减小,在650和700℃下退火4 h后高度敏化,再活化率Ra均大于30%,而在800℃退火4 h后未被敏化。     

Si、Mn元素对奥氏体不锈钢微观组织和拉伸性能的影响

为提高奥氏体不锈钢耐蚀性,合金中可同时加入Si、Mn元素,提高合金氧化膜形成能力,同时增加奥氏体基体稳定性,但Si、Mn的添加还能够对合金的冷变形组织和力学性能产生影响。本研究设计了不同硅、锰含量的奥氏体不锈钢,采用SEM、EPMA以及TEM等方法表征合金显微组织形貌,采用室温拉伸分析合金的力学性能。结果表明,Si质量分数由1.0%提高至2.0%,20%冷变形合金组织中变形孪晶体积分数由4.98%增加至8.33%,合金屈服强度由620 MPa提高至682 MPa,延伸率基本保持不变;Mn质量分数由1.5%提高至2.0%,变形孪晶体积分数由8.33%减少至7.22%,屈服强度由682 MPa降低至627 MPa,延伸率由16.0%增加至21.3%;添加Si元素,合金中孪晶数量增加,合金强度提高并保持塑性;添加Mn元素,合金中孪晶数量减少,强度降低塑性增强。     

高产天然气井放喷管汇弯管冲蚀磨损特性研究

目的 研究高产天然气井气固两相流对放喷管汇的冲蚀机理及规律.方法 利用CFD软件对放喷管汇冲蚀进行研究,使用雷诺平均Navier-Stokes(RANS)方程求其气相的运动状态,并用离散相模型(DPM)计算出颗粒运动轨迹.然后使用Oka冲蚀磨损模型开展弯管角度、弯管位置、放喷量等5种因素与壁面冲蚀规律研究,最后使用最大冲蚀速率、壁面质量损失以及管汇刺漏时间等3种指标评价管汇的冲蚀特性.结果 在控制单因素变量的前提下,随着含砂率从1％增长到5％时,弯管最大冲蚀速率增加了约4倍;随着放喷量从3.0×105 m3/d增加到5.1×106 m3/d时,最大值出现在1.0×106 m3/d附近,弯管最大冲蚀速率相比3.0×105 m3/d增加了3.7倍;当弯管角度从90°增加到165°时,最大冲蚀速率下降了85％,但120°弯管最大冲蚀速率最大;随着弯管距出口距离从5 m增加到30 m时,最大冲蚀速率下降了86％;当颗粒形状系数从0.67增加到1时,最大冲蚀速率增大了5倍.结论 含砂率与最大冲蚀速率相关度最大,弯管位置与最大冲蚀速率的相关度最小.最大冲蚀速率随含砂率、颗粒形状系数的增加而增大,随弯管角度和距出口直管段长度的增加而减小,但120°弯管冲蚀最严重.随放喷量的增加,弯管最大冲蚀速率呈现出先增大、后减小、最后趋于平稳的规律.     

锻造及热处理工艺对耐磨钢组织及耐磨性能的影响

研究了锻造变形量与热处理工艺对一种新型耐磨钢显微组织、硬度和耐磨性的影响,并用彩色金相法定量分析了钢中马氏体+残留奥氏体含量。结果表明:不同变形量下耐磨钢组织均为贝马复合相,贝氏体板条厚度由30%变形量的524 nm降低到70%变形量的292 nm,马氏体+残留奥氏体体积分数由25.4%增加至41.1%;与直接进行260 ℃等温转变时相比,先在Ms点以上的330 ℃保温5 min,再进行260 ℃等温转变时的贝氏体板条厚度减少了357.2 nm,磨损量降低了0.02 g,且平均摩擦因数由0.311降至0.212。     

泡沫铝发泡初期孔隙及气泡的形成与扩展

通过采用粉体致密化浸入式快速加热新工艺制备泡沫铝技术，研究了泡沫铝发泡早期气泡形成特征、早期气泡孔径结构特点及动态变化规律。结果表明：泡沫铝发泡历经以微膨胀、显著膨胀和塌陷收缩为特征的3个主要阶段；在发泡初期，微膨胀形成的机制主要是TiH2分解的H2，并受其受力状态所决定的，由此形成的裂纹式孔隙主要在固态，扩展方向呈横向特征。预制块的显著膨胀主要是由于TiH2的持续分解使裂纹式孔隙扩展长大的结果。由于新工艺加热升温迅速，发泡时间由一般的10min缩短为30—150s，使预制块固液态转换时间大大缩短，有效地提高了均匀发泡的动力学条件，同时还提高了TiH2的利用率。     

氧化铝碳热还原反应机制及其热力学

研究了球磨活化后氧化铝碳热还原反应合成氮化铝的机理 ,提出了通过氧化铝碳热还原反应合成氮化铝的新机制 :氧化铝首先发生氮化反应生成AlON相 ,AlON再还原氮化生成氮化铝。通过热力学计算得到的反应平衡温度与实验得到的氮化铝开始生成温度相吻合。     

HRB400热轧带肋钢筋铸坯质量缺陷原因分析及优化

针对HRB400连铸坯脱方、表面及内部裂纹问题,跟踪排查连铸生产过程,发现铸坯质量缺陷主要与结晶器振动参数、二冷工艺、足辊等因素有关。通过将结晶器振程由7.5 mm提高至8.5 mm,结晶器冷却水量由2 300 L/min降低至2 100 L/min,二冷比水量由1.30 L/kg提高至1.56 L/kg,安装结晶器足辊、挡水板,定期检修维护连铸喷嘴、对弧等措施,铸坯脱方率由1.5%降低至0.1%,角部裂纹发生率由3.2%降低至0.6%,中间裂纹不高于0.5级占比由8.3%提高至92.6%,中心裂纹不高于0.5级占比由85.0%提高至100%,铸坯质量明显改善,成品钢筋质量、性能符合要求。     

模铸系统结构对钢材探伤合格率的影响

研究了浇注系统结构对10～27t大钢锭成材后探伤合格率的影响.通过改进浇注系统结构,降低浇注过程中的夹渣几率,提高了钢材质量.改进后探伤不合格率由14.6％下降到25％,下降了83％.     

Anomalous oxidation of sintered porous steels in the process of steam oxide treatment

Parts manufactured by pressing from iron-base powders possess a certain porosity. The pores form a system of communicating capillaries inside the part which absorb the ambient products (gases from the atmosphere, dissolved substances from solutions) under the action of the capillary forces and diffusion. This causes surface and internal corrosion of the material. In order to prevent oxidation of parts produced from powder materials in their transportation, storage, and operation their surface should be coated by a thin oxide film (as in blueing) in which the pores are closed by the oxides. The results of a study of the composition of oxide phases in sintered porous steels after a steam oxide treatment by two regimes are presented. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 22–26, July, 1998.     

Atomistic origin of microstrain broadening in diffraction data of nanocrystalline solids

The origin of microstrain broadening in X-ray diffraction patterns of nanocrystalline metals is investigated by comparing data obtained from virtual diffractograms and from direct analysis of computer-generated samples. A new method is introduced that allows the local deformation gradient to be calculated for each lattice site in the microstructure from atomic coordinates obtained by molecular dynamics simulations. Our results reveal that microstrain broadening in undeformed samples cannot be attributed to lattice dislocations or strain fields near grain boundaries. The broadening arises, instead, from long-range correlated displacement fields that extend throughout the grains. The microstrain therefore provides a quantitative measure for distortions far from grain boundaries. This suggests that diffraction-based strategies for inferring the dislocation density in ultrafine-grained metals do not necessarily apply to nanocrystalline materials.     

葎草水提物止痒作用的实验研究

目的:研究草水提物的止痒作用。方法:通过采用4-氨基吡啶(4-AP) 诱发小鼠皮肤瘙痒反应、氯喹诱发小鼠全身瘙痒反应、组胺致豚鼠局部瘙痒反应及2, 4-二硝基氟苯(DNFB) 致小鼠右耳廓迟发型变态反应的瘙痒动物模型, 并用放射免疫分析方法(RIA) 测定氯喹致小鼠瘙痒后血清中IL-4 的含量, 观察草水提物的止痒作用。结果:草水提物100、 30 mg/kg 显著抑制4-AP 和氯喹诱发小鼠瘙痒反应的持续时间, 其中100 mg/kg可显著减少搔痒次数, 并显著降低氯喹诱发小鼠瘙痒反应后血清中IL-4 的含量; 草水提物25、 7. 5 mg/kg 显著提高豚鼠致痒阈;100、 30 mg/kg 显著抑制DNFB 致小鼠右耳廓肿胀。结论: 草水提物具有止痒作用, 可能与抑制组胺和IL-4 的释放有关。     

Development of the Polish wasteless technology of apatite phosphogypsum utilization with recovery of rare earths

The most promising source of rare earth elements in Poland is apatite phosphogypsum, a waste product obtained in the process of phosphoric acid production from Kola apatite. Depending on the technology used, as the hydration ratio of calcium sulphate is changed from hemihydrate to dihydrate, the content of rare earths varies from 0.6% to 0.3% Ln₂O₃ respectively. Technological flow charts for recovering the rare earths as a byproduct have been developed. The basic process used in the technology consists of three steps: apatite phosphogypsum leaching with dilute sulphuric acid solution; separation of rare earth concentrates from leaching sulphuric acid by preconcentration via evaporization, liquid-liquid extraction or precipitation method; anhydrite production from purified phosphogypsum by recrystallization in concentrated sulphuric acid solution.     

Inhibition by magnetic fields of the growth of zinc dendrites from alkaline zincate baths

Crystals of electrodeposited zinc films were observed directly and indirectly by metallurgical microscopy. The quantity of electricity used in the deposition was 18 C cm^-2, the current density ranged from 1.0 to 10.0 A dm^-2 and the magnetic flux density ranged from 0 to 0.125 T. The temperature of the test solutions ranged from 5 to 60 °C. The growth of dendrites was inhibited by the magnetic fields. Compared with the efficiencies in the absence of the magnetic field, the cathodic efficiency increased by about 5% – 10% and the anodic efficiency decreased by about 5% – 10%.     

Analysis of New Nitinol Ingot Qualities

New ingot qualities, processed by optimized vacuum arc remelting (VAR), optimized vacuum induction melting followed by VAR and VAR followed by electron beam remelting, were compared with standard quality. Finished components as well as diamond-shaped samples representing a typical dimension of self-expanding stents were produced using Nitinol tubing drawn from the new ingot qualities. Metallographic longitudinal sections were prepared and analyzed to determine inclusion size and distributions of the various ingot qualities. Radial force and uniaxial tensile tests were used to determine the mechanical properties of fully processed material and tubing, respectively. Transformation temperatures of tubing as delivered from supplier and processed stents were measured by differential scanning calorimetry and deformation-and-free-recovery testing. Finally, fatigue tests were performed on diamond-shaped samples to evaluate the strain-life characteristics of the new ingot qualities. Results of this study are compared to ADMEDES historical data from standard Nitinol materials to gain an assessment of the new improved ingot qualities with regard to the production of Nitinol vascular implants. The latest developments in Nitinol ingot quality are highlighted and the results of the comparison from technical point of view are shown.