阴极电流密度对6061铝合金在含Na_(2)WO_(4)电解液中微弧氧化膜结构和耐磨性能的影响

目的 研究恒流模式下阴极电流密度对6061铝合金在含Na2WO4的电解液中制备的微弧氧化膜厚度、形貌、相组成及耐磨性能的影响。方法 固定阳极电流密度为5.0 A/dm^(2),阴极电流密度分别为0、1.25、2.5、3.75、5.0 A/dm2,对6061铝合金进行微弧氧化40 min。用涡流测厚仪测量了氧化膜的厚度,用扫描电镜观察了微弧氧化膜的表面形貌和截面形貌,用能谱分析仪分析了氧化膜的表面成分,用X射线衍射分析仪分析了微弧氧化膜的相组成,用往复式摩擦磨损试验机测试了氧化膜的耐磨性能。结果 随着阴极电流密度的增加,氧化膜内的W含量逐渐减少,氧化膜颜色逐渐变浅,氧化膜厚度逐渐增加。微弧氧化膜的主要组成相为α-Al2O3和γ-Al2O3。当阴极电流密度从0 A/dm2增加到3.75 A/dm2时,氧化膜内孔洞的数量和尺寸逐渐减少,孔洞到氧化膜/基体界面的距离逐渐增加,氧化膜的耐磨性能逐渐提升。当阴极电流密度为3.75 A/dm2时,氧化膜的磨损率最低,仅为1.07×10-4mm3/(N·m)。但阴极电流密度增加到5.0 A/dm2时,氧化膜表层出现孔洞和剥落,耐磨性能下降。结论 阴极电流的加入有助于增加6061铝合金微弧氧化膜的厚度,提高氧化膜的致密性和耐磨性能,但过高的阴极电流会导致氧化膜表层出现孔洞,降低耐磨性能。

Effect of heat treatment on microstructures and mechanical properties of sand-cast Mg-4Y-2Nd-1Gd-0.4Zr magnesium alloy

Influence of heat treatment on the microstructures and mechanical properties of sand-cast Mg-4Y-2Nd-1Gd-0.4Zr magnesium alloy was investigated,and the tensile fracture mechanisms of the studied alloys under different conditions were also discussed.The results show that the optimum T4 and T6 heat treatment conditions for the as-cast Mg-4Y-2Nd-1Gd-0.4Zr alloy are 525°C,8 h and（525°C,8 h）＋（225°C,16 h）,respectively,with regard to the microstructure observation,DSC heating curve and mechanical properties.The hardness,yield strength,ultimate tensile strength and elongation of the Mg-4Y-2Nd-1Gd-0.4Zr alloy treated by optimum T6 heat treatment are HV91,180 MPa,297 MPa and 7.4%,respectively.Moreover,the Mg-4Y-2Nd-1Gd-0.4Zr alloys under different heat treatment conditions exhibit different tensile fracture modes.

Sealing Effect of KAl(SO_(4))_(2)Solution on the Corrosion Resistance of Anodized Aluminum Alloy

The 2024 anodized aluminum alloy film was sealed by KAl(SO_(4))_(2)solution and the effect of sealing on corrosion resistance was investigated by means of potentiodynamic polarization curves,electrochemical impedance spectroscopy,and X-ray photoelectron spectroscopy.The experimental results show that the optimal parameters for KAl(SO_(4))_(2)sealing are 35℃,with the pH value of 8,the concentration of 8 g/L,and the sealing time of 3 min.The corrosion resistance of the KAl(SO_(4))_(2)sealed sample can be significantly improved than that of unsealed one,and is obviously superior to that of the conventional hydrothermal sealed sample.Furthermore,X-ray photoelectron spectroscopy demonstrates that more Al(OH)_(3)will be formed in the process of KAl(SO_(4))_(2)sealing,which will shrink the diameter of the microporous and therefore results in the excellent corrosion resistance.

Hot deformation behaviors and dynamic recrystallization mechanism of Ti-35421 alloy inβsingle field

Hot deformation behaviors and microstructure evolution of Ti-3Al-5Mo-4Cr-2Zr-1Fe(Ti-35421)alloy in theβsingle field are investigated by isothermal compression tests on a Gleeble-3500 simulator at temperatures of 820-900°C and strain rates of 0.001-1 s^(-1).The research results show that discontinuous yield phenomenon and rheological softening are affected by the strain rates and deformation temperatures.The critical conditions for dynamic recrystallization and kinetic model of Ti-35421 alloy are determined,and the Arrhenius constitutive model is constructed.The rheological behaviors of Ti-35421 alloys aboveβphase transformation temperature are predicted by the constitutive model accurately.The EBSD analysis proves that the deformation softening is controlled by dynamic recovery and dynamic recrystallization.In addition,continuous dynamic recrystallization is determined during hot deformation,and the calculation model for recrystallization grain sizes is established.Good linear dependency between the experimental and simulated values of recrystallized grain sizes indicates that the present model can be used for the prediction of recrystallized grain size with high accuracy.

Characteristics of Faigue Crack Initiation in Ti-5Al-4Sn-2Zr-1Mo-0.7Nd-0.25Si Alloy

The characteristics of fatigue crack initiation in Ti-5AI-4Sn-2Zr1Mo-O.7Nd-O.25Si alloy wereStudied. Two modes Of fatigue crack initiation were found. The Nd-rich phase particles displaybetter resistance to fatigue crack initiation than the matrix at lower stress.

Intragranular Rare Earth－rich Phases in As－cast High－temperature Ti－5Al－4Sn－2Zr－1MO－0．25Si－1Nd Alloy

In the as-cast Ti-55 alloy, the intragranular rare earth-rich phase particles are about 1. 0～14 μm in diameter, elliptical, and rich in Nd, Sn, and O. The contents of Nd and Sn on the grain boundaries are higher than those at other sites. The intragranular phases grow preferably at the region on the grain boundaries, which causes the formation of the elliptical morphology of the intragranular phases.

合金碳化物与2(1/4)Cr-1Mo钢的韧化机制

用相分析手段研究了２１４Ｃｒ－１Ｍｏ钢回火过程中合金碳化物类型、含量、分布等与韧性的关系，并对其韧化机制进行了探讨。

Microstructure of Mg-8Zn-4Al-1Ca aged alloy

The microstructure of Mg-8Zn-4Al-1Ca aged alloy was investigated by TEM and HRTEM. The results show that the hardening produced in the Mg-8Zn-4Al-1Ca alloy is considerably higher than that in the Mg-8Zn-4A1 alloy. A dense dispersion of disc-like Ca2Mg6Zn3 precipitates are formed in Mg-8Zn-4Al-1Ca alloy aged at 160 ℃ for 16 h. In addition, the lattice distortions, honeycomb-looking Moir＆#233; fringes, edge dislocations and dislocation loop also exist in the microstructure. The precipitates of alloy aged at 160 ℃ for 48 h are coarse disc-like and fine dispersed grainy. When the alloy is subjected to aging at 160 ℃ for 227 h, the microstructure consists of numerous MgZn2 precipitates and Ca2Mg6Zn3 precipitates. All the analyses show that Ca is a particularly effective trace addition in improving the age-hardening and postponing the formation of MgZn2 precipitates in Mg-8Zn-4Al alloy aged at 160 ℃.

镍铜合金NCu30-4-2-1电渣熔铸件的热变形行为

在Gleeble-3800热模拟机上对电渣熔铸态镍铜合金NCu30-4-2-1进行高温热压缩实验,研究该合金在900～1 100℃和应变速率为0.01～10 s-1条件下的流变应力行为。结果表明:在变形初期,随着应变的增加,流变应力增大,出现峰值后逐渐趋于平稳;随着温度的升高,峰值应力减小,而随着应变速率的增大,峰值应力增大,求得镍铜合金NCu30-4-2-1的热变形激活能Q为416.5 kJ/mol,Zener-Hollomon参数的对数和峰值应力的对数较好地满足线性关系,建立了镍铜合金NCu30-4-2-1的流变应力方程;合金的显微组织受变形温度和显微组织的影响,变形温度越高,应变速率越低,越有利于动态再结晶的发生。

Microstructures and mechanical properties of MgAl_2O_4 particle-reinforced AC4C aluminum composites

MgAl2O4 particle-reinforced AC4C based alloy composites were fabricated by the stirring-casting method. The effects of the average sizes and the size distributions of MgAl2O4 particles on the dispersibility were investigated, and the microstructures, strength, and fatigue properties of MgAl2O4 particle-reinforced AC4C based alloy composites were evaluated. Tensile strength in the MgAl2O4 particle-reinforced AC4C based alloy composite was increased by using the classified particles. The fatigue limit at 107 cycles in the MgA1204 particle-reinforced AC4C-Cu composite increased by 27% compared to the unreinforced alloy at 250 ~C. Dislocations were observed in the matrix around the MgAl204 particle which resulted from the mismatch of thermal expansion coefficients between MgAl2O4 and Al, and resisted failure and caused fatigue cracks to propagate around the MgAl2O4 particles, resulting in extensive crack deflection and crack bowing which contributed to the improvement of fatigue strength.

Volta Potential Analysis of Intermetallics in 7A52 Aluminum Alloy

In order to study the effect of intermaetallics on the corrosion behaviour of 7A52 aluminum alloy, the alloy was characterized by means of SEM-EDS and scanning Kelvin probe force microscopy（SKPFM）. The experimental results indicate that there are two different intermetallics：A1-Mn-Fe and Mg2Si. Both intermetallics exhibite the negative volta potential relative to the matrix indicating an anodic behaviour. Hereby, they are easy to be dissolved and corroded under the erosive environment, and there become the corrosion initiation sites. The A1-Mn-Fe intermetallics show stronger anodic behaviour than those of Mg2Si intermetalics. It means that A1-Mn-Fe intermetalics are easier to be corroded.

新显色剂2,6-二碘-4-硝基偶氮胂与锆显色反应研究及应用

研究了新显色剂2-(2-胂酸基苯偶氮)-7-(2,6-二碘-4-硝基苯偶氮)-1,8-二羟基-3,6-萘二磺酸与锆的显色反应.在1.92mol/LHCl介质中,试剂与锆生成蓝色配合物,最大吸收波长633nm,摩尔吸光系数为4.37×104L/(mol·cm),显色酸度高,常见的共存离子允许量特别大,选择性好.0～20μg/(25mL)Zr(IV)符合比耳定律,以NaF褪色试样空白为参比,直接吸光光度法测定合金钢中的微量锆,方法简便,结果可靠.

5083 H321铝合金板材制备组织性能研究

基于“1+4”热连轧生产线、2800mm冷轧生产线,采用不同工艺线路制备了5083 H321铝合金板材,研究了不同制备工艺对板材组织性能的影响。结果表明,不同工艺路线成品板材力学性能、耐腐蚀性能及微观组织均存在明显差异。采用“1+4”热连轧生产线短流程工艺制备的5083 H321铝合金板材性能:抗拉强度358MPa、屈服强度257MPa、延伸率17%、剥落腐蚀等级PA、晶间质量损失3.22mg/cm2。

Improving Joint Features and Mechanical Properties of Pinless Fiction Stir Welding of Alcald 2A12-T4 Aluminum Alloy

As a new solid state welding,pinless friction stir welding（PFSW） can be used to join thin-wall structures.In this study,four new pinless tools with different groove distributions were designed and manufactured in order to enrich technological storage of PFSW and obtain sound joint with high quality of alclad 2A12-T4 alloy.The results show that the small-obliquity tool is detrimental to the transfer of plasticized materials,resulting in the formation of kissing bond defect.For the through-groove tool or the large-curvature tool,bigger flashes form on the joint surface and alclad layer is observed in the nugget zone（NZ）,deteriorating mechanical properties.Compared with the above-mentioned three tools,using the six-groove tool with rational curvature and obliquity can not only yield sound joint with small flashes and thickness reduction,but also prevent alclad from flowing into NZ,which has potential to weld thin alclad aluminum alloys.Meanwhile,the tensile strength and elongation of joint using the six-groove tool reach the maximum values of 362 MPa and 8.3%,up to 85.1% and 64% of BM.

Microstructure and properties of ultra-fine tungsten heavy alloys prepared by mechanical alloying and electric current activated sintering

The microstructure and properties of the 93W-4Ni-2Co-1Fe(mass fraction,%) tungsten heavy alloys prepared by mechanical alloying and electric current activated sintering from mixed elemental powders were investigated.After 15 h milling,the average W grain size in the powders is decreased to 120 nm.For the powders milled for 15 h,the density,hardness and transverse rupture strength of the alloys sintered only by an intensive pulse electric current are the maximum.When the total sintering time keeps constant,the properties of the sintered alloys can be obviously improved by optimizing the sintering time of pulse-and constant-currents.A bulk ultrafine alloy with an average W grain size of about 340 nm can be obtained by sintering 15 h-milled powders in a total sintering time of 6 min.The corresponding sintered density,hardness and transverse rupture strength reach 16.78 g /cm3,HRA84.3 and 968 MPa,respectively.

Effect of K2TiO(C2O4)2 Addition in Electrolyte on the Microstructure and Tribological Behavior of Micro-Arc Oxidation Coatings on Aluminum Alloy

Micro-arc oxidation （MAO） coatings with different concentrations of K2TiO（C2O4）2 in the sodium silicate base electrolyte were prepared on 6061 aluminum alloy with the aim of promoting a better understanding of the formation mechanisms and tribological behaviors of the coatings. Scanning electron microscopy （SEM） assisted with energy-dis- persive X-ray spectroscopy （EDS）, X-ray photoelectron spectroscopy （XPS） and friction test were employed to charac- terize the MAO processes and microstructure of the resultant coatings. Results showed that the composition and microstructure of the coatings were significantly affected by the addition of KETiO（CaO4）2. A sealing microstructure of MAO coating was obtained with the addition of K2TiO（C2O4）2. Ti element from K2TiO（C2O4）2 was only absorbed into the defects of micropores under surface energy in the early stage, while in the later stage, Ti element was predominant in the micropores and distributed on the coatings under plasma discharge to form TiO2. It was demonstrated that Ti and Si elements from the electrolyte could interact with each other during the MAO process and the interaction mechanism was systematically analyzed. Wear resistance of the MAO coatings with K2TiO（C2O4）2 addition was significantly improved compared with that of the MAO coatings without K2TiO（C2O4）2 addition.

1,2-二甲基-3-羟基-4-吡啶酮和牛磺酸联合干预对铝染毒大鼠大脑皮层抗氧化系统的保护作用

目的探讨1,2-二甲基-3-羟基-4-吡啶酮(deferipone,DFP)和牛磺酸联合作用对染铝大鼠大脑皮层抗氧化系统的影响。方法将70只健康SPF级雄性Wistar大鼠按体重随机分为7组,以灌胃方式染毒,其中,阴性对照组给予1 ml生理盐水,连续8周;铝染毒组、牛磺酸干预组、低剂量DFP干预组、高剂量DFP干预组、牛磺酸+低剂量DFP干预组和牛磺酸+高剂量DFP干预组在前4周分别给予281.40 mg/kg三氯化铝溶液,后4周分别给予1 ml生理盐水、400 mg/kg牛磺酸、13.82 mg/kg DFP、27.44 mg/kg DFP、400 mg/kg牛磺酸、400 mg/kg牛磺酸;牛磺酸+低剂量DFP干预组和牛磺酸+高剂量DFP干预组给予400 mg/kg牛磺酸6 h后分别给予13.82、27.44 mg/kg DFP,每天1次。测定大鼠大脑皮层SOD、GSH-Px活力和MDA含量。结果与阴性对照组比较,铝染毒组大鼠大脑皮层SOD和GSH-Px活力均较低,而MDA含量较高,差异有统计学意义(P<0.05)。与铝染毒组相比,在单独干预组中,仅高剂量DFP干预组可以显著提高SOD和GSH-Px活力,降低MDA的含量;牛磺酸干预组可以显著提高GSH-Px的活力水平以及降低MDA含量。在DFP和牛磺酸的联合作用下,大鼠大脑皮层的SOD和GSH-Px活力水平以及MDA含量均基本恢复正常。其中,与牛磺酸干预组和低剂量DFP干预组比较,牛磺酸+DFP干预组可以显著提高SOD和GSH-Px活力,降低MDA含量;且以牛磺酸+低剂量DFP干预组尤为显著。结论在本实验剂量范围内,牛磺酸和DFP联合干预可以对染铝大鼠大脑皮层的抗氧化系统起到保护作用,且效果优于牛磺酸或DFP单独干预。

热处理对NCu30-4-2-1合金组织与性能的影响

本文采用差示扫描量热仪及透射电子显微镜研究了热处理工艺对NCu30-4-2-1合金组织及性能的影响。结果表明,固溶温度为850℃时,合金组织变化不明显;随着固溶温度的提高,枝晶间共晶组织逐渐溶解,当固溶温度为950℃时,枝晶组织基本消失,合金中β强化相基本溶入固溶体基体中,形成单相过饱和固溶体组织;继续提高固溶温度至1050℃时,晶粒异常长大。增加时效温度和时间,合金硬度值先增大,达到峰值后趋于平稳。合金经时效处理600℃×8 h,主要析出相为细小弥散分布的β'-Ni3Si相,并与基体保持良好共格关系,合金强度硬度最大,断后伸长率较高。

硅酸盐体系电解液中添加Na_(2)WO_(4)对LY12铝合金陶瓷膜性能的影响

通过SEM、XRD、硬度试验、电化学腐蚀试验研究了在硅酸盐体系电解液中加入不同浓度的Na_(2)WO_(4)对LY12铝合金微弧氧化陶瓷膜表面形貌及性能的影响。结果表明,添加Na_(2)WO_(4)改变了膜层的微观结构,使微弧氧化膜层硬度增加,表面平滑,呈现出小而少的孔洞结构,且表面堆积少量形状不规则的白色质点;随着Na_(2)WO_(4)添加量的增加,膜层的硬度值呈现先增加后降低的趋势,当Na_(2)WO_(4)含量为4 g/L时,膜层达到最高硬度440.3 HV0.3,较基体(硬度值约168 HV0.3)提升了272.3 HV0.3;XRD分析证明W元素参与了微弧氧化过程,并生成W的氧化物WO_(3),陶瓷层物相主要由α-Al_(2)O_(3)和γ-Al_(2)O_(3)以及WO_(3)组成;电化学极化曲线分析结果表明添加剂Na_(2)WO_(4)有效地提高了膜层的耐腐蚀性能,耐腐蚀性能最好的添加量为1 g/L,此时自腐蚀电位为-532.0 mV,腐蚀电流为0.011μA。Na_(2)WO_(4)的添加可有效改善陶瓷膜层的表面形貌及性能。综合考虑膜层的性能,添加剂Na_(2)WO_(4)的最佳添加量为4 g/L。

不同复盐电解液中NaVO_(3)对铝合金微弧氧化热控膜层结构和性能影响的对比研究

目的在以Na_(2)SiO_(3)为主导的Na_(2)SiO_(3)-Na_(3)PO_(4)复盐电解液和以Na_(3)PO_(4)为主导的Na_(3)PO_(4)-Na_(2)SiO_(3)复盐电解液中加入相同浓度梯度的NaVO_(3),研究着色盐NaVO_(3)对微弧氧化膜层结构的影响,分析膜层的黑度、热控性能、耐蚀性和结合力的变化。方法在A356铝合金表面制备微弧氧化膜层,采用比例分割分批法设计试验。利用ColorReader、涡流测厚仪、SEM、EPMA、EDS、LSCM、XRD、辐射计、太阳光谱反射计,分别表征膜层的颜色、厚度、微观形貌、元素分布、表面粗糙度、物相组成、发射率和吸收率。采用电化学、点滴及盐雾等实验检测膜层耐蚀性,采用热震实验检测结合力。结果在2种复盐电解液中,当NaVO_(3)的质量浓度均为12.06 g/L时,所得膜层颜色最深,且Na_(3)PO_(4)主盐系的颜色更深,其黑度值可低至20.31;热控性能最佳,吸收率和发射率分别高达0.934、0.888;加入着色盐NaVO_(3)后,微弧氧化膜表面出现了自封孔现象,对提高膜层耐蚀性很有利,Na_(3)PO_(4)主盐系膜层的耐蚀性优于Na_(2)SiO_(3)主盐系的,而且也是当NaVO_(3)的质量浓度为12.06 g/L时,膜层的耐蚀性最好;此时,Na_(3)PO_(4)主盐系膜层抗热冲击的次数可高达65。结论在2种复盐电解液中加入着色盐NaVO_(3)后,沉积出了使膜层显深色的钒氧化物。当NaVO_(3)的质量浓度为12.06 g/L时,在各自体系中均可获得同时具有优良耐蚀性、良好结合力、高吸收率、高发射率的热控膜层,且Na_(3)PO_(4)主盐系膜层的性能略高一筹。