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1.
Jin-Ke Yu ;Hong-Wei Li ;Qi-Jie Zhai ;Jian-Xun Fu ;Zhi-Ping Luo ;Hong-Xing Zheng 《上海大学学报(英文版)》2014,(4):353-357
In the present work, crystal structure and for- mation mechanism of the secondary phase in Heusler Ni- Mn-Sn-Co materials were investigated using X-ray dif- fraction, scanning/transmission electron microscopy and selected-area electron diffraction techniques. Experimental results showed that the secondary phase presented in both Ni44.1Mn35.1Sn10.8Co10 as-cast bulk alloy and melt-spun ribbon, possessing a face-centered cubic （fcc） NilTSn3-type structure. The secondary phase in the as-cast bulk alloy was resulted from a eutectic reaction after the formation of a primary dendritic flphase during cooling. However in the melt-spun rapidly solidified ribbon, the secondary phase was largely suppressed as nano-precipitates distributed along the grain boundaries, which was attributed to a divorced eutectic reaction. The secondary phase exhibited partial amorphous state due to high local cooling rate. 相似文献
2.
Hot extrusion was conducted in the α+β phase region for promoting mechanical properties of Ti42Al9V0.3Y. The microstructures and tensile properties before and after hot extrusion were studied. The results show that the microstructure of the as-cast alloy mainly consists of massive γ phase in β matrix and the as-extruded alloy mainly consists of lamellar α2/γ, lamellar β/γ, and strip γ propagating from elongated β phase. In the as-cast alloy, the predominantly observed fracture mode is transgranular cleavage failure at room temperature and intergranular fracture at 650-750 °C. After hot extrusion, it transforms into transgranular cleavage-like failure, including translamellar cleavage and delamination. The excellent tensile properties of the as-extruded material are attributed to the obvious refined microstructure with broken YAl2 particles and the micro-crack shielding action of the TiAl lamellasome. 相似文献
3.
The corrosion process of tinplate in deaerated functional beverage was investigated by using electrochemical impedance spectroscopy (EIS) combined with scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) techniques. The results reveal that the uncoated tinplate shows a poor corrosion resistance and the corrosion type is detinning. During the initial stage of immersion, EIS spectrum consisted of two capacitance arcs with obvious time-constant dispersion effect, which was attributed to the two-dimensional and three-dimensional inhomogeneous distribution of the electrode surface. With the increase of immersion time, the capacitance arc of high frequency shrunk and degenerated, due to the corrosion of tin coating. The pore resistance of tin coating and the charger transfer resistance of substrate, which are determined from the electrochemical equivalent circuit, can be used as the indicators of tinplate corrosion process. The decrease of the pore resistance of tin coating indicates that the corrosion degree of tin layer becomes more severe, whereas the decrease of the charger transfer resistance of substrate implies that the corrosion degree of steel substrate also becomes more severe as the immersion time prolongs. 相似文献
4.
In order to research the bond properties between corroded reinforcement bars and concrete, reinforcement bars with different diameters and different types and concrete with different strength levels were treated specially with all soaking and impressed current method, and the bond properties were measured with the pull-out test. The comparative analysis of the bond properties of corroded reinforcement bars was carried out. The results showed that the types of reinforcement bars and concrete had great influence on the bond strength. The corrosion and volume expansion of reinforcement bars made concrete in tensile condition, which tended to produce cracks in parallel reinforced direction. The typical bond failure of plain reinforcement bars was pull-out, while the typical bond failure of ribbed reinforcement bars was split. The bond strength between corroded reinforcement bars and concrete increased with the increase of concrete strength. The bond strength of plain and ribbed reinforcement bars showed a decreasing trend after the first increase with the increase of the extent of corrosion. Through the test, the coefficients of the bond strength of plain and ribbed reinforcement bars were given, respectively. 相似文献
5.
Corrosion is one of the main causes of deterioration in steel structures. Loss of thickness in flanges and web of corroded steel beams leads to reduction in section properties which can reduce the lateral torsional buckling capacity of the member. In this paper, thickness loss data were compiled from four samples of corrosion damaged I-beams removed from a petro-chemical plant. Visual examination of the four corroded beams showed that they were corroded uniformly. To improve the accuracy of the results, a large number of measurements for surface roughness were taken for each beam, totally 770 values to obtain the average thickness of flanges and web of each beam. The data was used to develop a corrosion decay model in order to calculate the percentage remaining lateral torsional buckling capacity of long and short span beams which are laterally unrestrained. To estimate the percentage of remaining lateral torsional buckling capacity in the corroded damaged I-beams, the readily available minimum curves for different types of universal beams in conj unction with information on the thickness loss were used. The results can be used by practicing engineers for better estimation on the service life of deteriorated steel structures. 相似文献
6.
Zhu Yu Song Yang Xu Likun Qin Zhenbo Song Shizhe Hu Wenbin Xia Da-Hai 《天津大学学报(英文版)》2020,26(3):218-227
Stainless steel(SS) is one of the most widely used engineering materials in marine engineering. However, its corrosion in the marine atmospheric environment due to the high concentration of Cl~- is a problem. The SS corrosion is a threat to the development and security of marine industry; therefore, evaluating the corrosion resistance of SSs is necessary. In this work, atmospheric corrosion detection probes based on a symmetrical electrode system were used to study the corrosion behaviors of 304 SS and 2205 duplex stainless steel(DSS) in a simulated marine atmosphere. A theoretical model for electrochemical noise(EN) data analysis based on the Thevenin electrochemical equivalent circuit(EEC) model was established. The relationship between the EN characteristic parameters and the corrosion rate was obtained. The Thevenin EEC model analysis showed that the relationship between the noise resistance( R_n), the noise impedance [ R_(sn)(f)], and the impedance modulus(| Z( f)|) was R_n≈ R_(sn)=■. Thus, R_n and R_(sn) can be used as indicators for quantitative corrosion evaluation. The results of EN detection for the 304 SS and 2205 DSS showed that in a simulated marine atmospheric environment, the passive fi lms on the two SSs were relatively intact at the initial exposure stage, and their dissolution rates were slow. The corrosion resistance of the 2205 DSS was higher than that of the 304 SS. With the deposition of Cl~- on the SS surface, pitting was initiated and the dissolution rate increased. The pitting initiation process on the SS surface was random, and part of the active pores could be repassivated. 相似文献
7.
Evolution of Surface Oxide Film of Typical Aluminum Alloy During Medium-Temperature Brazing Process简 总被引：1，自引：0，他引：1
The evolution of the surface oxide film along the depth direction of typical aluminum alloy under medium-temperature brazing was investigated by means of X-ray photoelectron spectroscopy （XPS）. For the alloy with Mg content below 2.0wt%, whether under cold rolling condition or during medium-temperature brazing process, the en-richment of Mg element on the surface was not detected and the oxide film was pure Al2O3. However, the oxide film grew obviously during medium-temperature brazing process, and the thickness was about 80 nm. For the alloy with Mg content above 2.0wt%, under cold rolling condition, the original surface oxide film was pure Al2O3. However, the Mg element was significantly enriched on the outermost surface during medium-temperature brazing process, and MgO-based oxide film mixed with small amount of MgAl2O4 was formed with a thickness of about 130 nm. The alloy-ing elements of Mn and Si were not enriched on the surface neither under cold rolling condition nor during medium-temperature brazing process for all the selected aluminum alloy, and the surface oxide film was similar to that of pure aluminum, which was almost entire Al2O3. 相似文献
8.
This study investigated characteristics of bifurcation and critical buckling load by shape imperfection of space truss,which were sensitive to initial conditions.The critical point and buckling load were computed by the analysis of the eigenvalues and determinants of the tangential stiffness matrix.The two-free-nodes example and star dome were selected for the case study in order to examine the nodal buckling and global buckling by the sensitivity to the eigen buckling mode and the analyses of the influence,and characteristics of the parameters as defined by the load ratio of the center node and surrounding node,as well as rise-span ratio were performed.The sensitivity to the imperfection of the initial shape of the two-free-nodes example,which occurs due to snapping at the critical point,resulted in bifurcation before the limit point due to the buckling mode,and the buckling load was reduced by the increase in the amount of imperfection.The two sensitive buckling patterns of the numerical model are established by investigating the displaced position of the free nodes,and the asymmetric eigenmode greatly influenced the behavior of the imperfection shape whether it was at limit point or bifurcation.Furthermore,the sensitive mode of the two-free-nodes example was similar to the in-extensional basis mechanism of a simplified model.The star dome,which was used to examine the influence among several nodes,indicated that the influence of nodal buckling was greater than that of global buckling as the rise-span ratio was higher.Besides,global buckling is occurred with reaching bifurcation point as the value of load ratio was higher,and the buckling load level was about 50%-70% of load level at limit point. 相似文献
9.
Jaleel CA Gopi R Manivannan P Kishorekumar A Gomathinayagam M Panneerselvam R 《Journal of Zhejiang University. Science. B》2007,8(4):283-288
The ability of triadimefon(TDM),a triazolic fungicide,to alter the biochemical constituents and thereby minimizing the days required for sprouting in white yam(Dioscorea rotundata Poir.) tubers during storage under(30±2) °C in the dark,was studied.TDM at 20 mg/L was given to tubers by dipping the tubers in treatment solution containing 20 mg/L TDM on 10,25 and 40 d after storage(DAS).Starch,sugars,protein,amino acid contents as well as protease and α-amylase activities were estimated on 15,30 and 45 DAS from two physiological regions viz.,apical and basal regions of the tubers.In normal conditions(control) sprouting occurred on 70 to 80 DAS.The starch content decreased,while protein,amino acid,sugar contents and protease and α-amylase activities were increased due to TDM treatment and led to early sprouting. 相似文献
10.
In this research, the changing rules of billet forged Ti-22 Al-24 Nb alloy with various solution time were studied, and the mechanical properties of different microstructure were tested at the room temperature. The results indicate that the(α2+O+B2) three-phase microstructure with equiaxed grains was acquired by Ti-22 Al-24 Nb alloy billet forging, and the average size of the grains was about 300 μm. With the increase of solution time, the primary lath-shaped O phase began to dissolve, and then the equiaxial α2 phase started to dissolve, but the undissolved α2/O phase began to be equiaxial and grow. The grains of original B2 phase recrystallized and grew. After the 2 h solution treatment, the recrystallization of grains was completed basically and the average size of the grains was about 100 μm. After the 2.5 h solution treatment, the strength of the alloy decreased, and the plasticity increased. However, when the solution treatment increased to 3 h, the plasticity decreased but the strength increased. The optimal solution parameters of Ti-22 Al-24 Nb alloy were the holding time of 2 h, the solution temperature of 1 000 ?C, and water cooling. Excellent comprehensive mechanical properties can be accquired under these parameters. The tensile strength, the yield strength, the elasticity modulus, the elongation, and the section shrinkage were 950 MPa, 915 MPa, 90 GPa, 15.69% and 42.28%, respectively. 相似文献
11.
采用“烧结-球磨”方法制备Mg0．92 In0．05 Zn0．03三元固溶体合金,减小了Mg的晶格常数.利用粉末X-射线衍射分析合金的相组成、微观结构和吸放氢过程的相转变,通过扫描电镜观察合金的微观形貌及相分布.采用体积法测定合金的等温吸放氢曲线（ PCT）和动力学曲线,确定了合金的吸放氢反应焓变、熵变及氢化反应激活能.结果表明： Mg0．92 In0．05 Zn0．03三元固溶体具有良好的活化性能和动力学性能,脱氢反应焓降低至-68．6 kJ/mol H2. 相似文献
12.
用成核-晶化隔离法制备了MgAl-CO3-LDHs,借助于TG-DSC、IR、XRD、SEM对其结构和形貌进行了表征。通过热老化箱实验研究了季戊四醇对PVC镁铝水滑石钙锌皂热稳定系统(Mg0.677Al0.323-CO3-LDHs/Ca(st)2/Zn(st)2)的增效性。结果表明,快速成核的等量盐、碱混合液,在100℃下回流晶化6h所得的水滑石Mg0.677Al0.323-CO3-LDHs为规整的层状晶体结构,层间距0.7455nm、晶轴a=0.3038nm、c=2.2365nm,在ac、方向的一次性晶粒分别是14nm和25.7nm。层间结晶水、层板羟基和层间阴离子CO32-脱除温度分别是249.5℃和422.1℃;含适量季戊四醇的热稳定剂系统较不含季戊四醇的初期着色和热稳定时间延长50min,分别达260min和290min。 相似文献
13.
用成核-晶化隔离法制备了层状MgZnAl-CO3纳米晶,借助于TG-DSC、IR、XRD、SEM和热老化箱对其结构、形貌及其与Ca（st）2/Zn（st）2复配对PVC热稳定性的协同效应进行了系统研究。结果表明,层板上半径为0.065nmMg2＋被半径为0.074nmZn2＋同晶取代后,Mg0.51Zn0.167Al0.323-CO3较Mg0.677Al0.323-CO3层间结晶水、层板羟基和层间阴离子CO32-脱除温度分别下降14.0℃和8.4℃,层板OH伸缩振动、层间结晶水弯曲振动和层间CO32-反对称振动吸收峰向高波数方向移动,（003）晶面间距从0.7455nm增加到0.7508nm、a（或b）和c轴长度分别从0.3038nm和2.2365nm增加到0.3044nm和2.2524nm;由于一定量的Mg0.51Zn0.167Al0.323-CO3与Ca（st）2/Zn（st）2的协同作用,PVC的初期着色和热稳定时间分别为250min和275min。 相似文献
14.
刘雪华林伟明商川杨斯盛 《福建工程学院学报》2020,(3):241-245
结合溶胶-凝胶法和化学镀方法,于镁合金基材表面成功制备了均匀的复合Ni-P-SiO_2/TiO_2/Al_2O_3镀层,采用扫描电镜(SEM)、光学显微镜(OM)、摩擦磨损试验及电化学方法,对比研究了Mg基材、基础Ni-P镀层与3种复合镀层的显微组织结构、耐磨性及耐腐蚀性。结果表明,加入3种溶胶所制备的复合镀层较Mg基材大幅度提高耐磨性和耐腐蚀性;3种复合镀层较Ni-P镀层具有更加均匀、致密的显微形貌,减少了直接加入纳米粉末的团聚,同时耐磨和耐蚀性改善。其中Ni-P-SiO_2复合镀层具有较高的显微硬度(HV513)和最低的摩擦系数(0.34),最高的腐蚀电位(-1.18V)及较小的腐蚀电流密度(9.5×10~(-3)mA·cm~(-2))。综合制备最佳工艺,并考虑节能减排因素,Ni-P-SiO_2复合镀层可作为性能优良的Mg合金耐磨、耐腐蚀镀层使用,于实际工业生产大有裨益。 相似文献
15.
结合发电厂凝汽器铜管在循环冷却水中产生腐蚀破坏的实际,对腐蚀部位和非腐蚀部位的微观组织进行的金相检测表明:凝汽器铜管点蚀深度达0.125～0.138mm;在腐蚀照片上,还可见到黄铜的层式和拴式脱锌,在铜合金管的某些部位腐蚀溶除后,基体上留下了一个蚀度了的残余结构. 相似文献
16.
李昱材 《宁波职业技术学院学报》2006,10(2):108-110
综述了Mg及Mg合金的腐蚀原理,以及合金中各元素在镁合金中的作用,并介绍了Mg合金几种典型的防护方法:提高合金纯度;开发新类型的合金;采用先进的加工工艺等。 相似文献
17.
用火焰原子吸收法测定了柳树种子中的Ca、Zn、Fe、Cu、K、Na、Co、Ni、Mn、Cr、Mg等微量元素,为柳树种子资源的开发提供了依据.各元素的回收率在92%～105%.结果表明,柳树种子富含人体所需的微量元素及大量元素. 相似文献
18.
用原子吸收光谱法对杭白菊（Chrysanchemum morifolitm Ramat）及黄山贡菊（Dendranthemamor folium）的Zn,Mn,Cu,Mg和Ph等微量元素进行了测定分析．该方法的标准曲线相关系数为0．99554～0．99986,相对标准偏差（RSD）小于2％．结果表明：杭白菊与黄山贡菊中Fe,Ca,Mg的含量均较高,黄山贡菊Ca,Zn,Cu,Mn含量较高,尤其是Mn．测定水洗后菊花和未水洗菊花中的微量元素含量可为人们日常饮用菊花的方式提供依据． 相似文献
19.
用原子吸收光谱法对银杏叶中十三种矿物元素进行了分析测定,结果显示,本方法精密度和回收率较好.在选定的实验条件下,银杏叶中各元素间相互不干扰,可在一份样品液中进行13种元素的分别测定;所测银杏叶中含有丰富的Ca、K、Mg、Fe、Mn、Zn以及Cu、Ni,有毒金属Pb、Cd被检出,加标回收率在86.03%-113.81%之间,RSD≤3.6(n=6). 相似文献