Effects ofslip mode on microstructure evolution and compressive flow behavior of extruded dilute Mg−0.5Bi−0.5Sn−0.5Mn alloy

The influence of the slip mode on the microstructure evolution and compressive flow behavior at different strains in an extruded dilute Mg−0.5Bi−0.5Sn−0.5Mn alloy was analyzed through electron backscatter diffraction,X-ray diffraction,transmission electron microscopy,and hot compression tests.The results showed that at a low strain of 0.05,the basal,pyramidaland<c+a>slip modes were simultaneously activated.Nevertheless,at the middle stage of deformation(strain of 0.1,0.2 and 0.5),theslip mode was difficult to be activated and<c+a>slip mode became dominant.The deformation process between strains of 0.2 and 0.5 was primarily characterized by the softening effect resulting from the simultaneous occurrence of continuous dynamic recrystallization and discontinuous dynamic recrystallization.Ultimately,at strain of 0.8,a dynamic equilibrium was established,with the flow stress remaining constant due to the interplay between the dynamic softening brought about by discontinuous dynamic recrystallization and the work-hardening effect induced by the activation of the basalslip mode.

Correlation of work function and stacking fault energy through Kelvin probe force microscopy and nanohardness in diluteα-magnesium

Electronic interactions of the Group 2A elements with magnesium have been studied through the dilute solid solutions in binary Mg-Ca,Mg-Sr and Mg-Ba systems.This investigation incorporated the difference in the‘Work Function'(ΔWF)measured via Kelvin Probe Force Microscopy(KPFM),as a property directly affected by interatomic bond types,i.e.the electronic structure,nanoindentation measurements,and Stacking Fault Energy values reported in the literature.It was shown that the nano-hardness of the solid-solutionα-Mg phase changed in the order of Mg-Ca>Mg-Sr>Mg-Ba.Thus,it was shown,by also considering the nano-hardness levels,that SFE of a solid-solution is closely correlated with its‘Work Function'level.Nano-hardness measurements on the eutectics andΔWF difference between eutectic phases enabled an assessment of the relative bond strength and the pertinent electronic structures of the eutectics in the three alloys.Correlation withΔWF and at least qualitative verification of those computed SFE values with some experimental measurement techniques were considered important as those computational methods are based on zero Kelvin degree,relatively simple atomic models and a number of assumptions.As asserted by this investigation,if the results of measurement techniques can be qualitatively correlated with those of the computational methods,it can be possible to evaluate the electronic structures in alloys,starting from binary systems,going to ternary and then multi-elemental systems.Our investigation has shown that such a qualitative correlation is possible.After all,the SFE values are not treated as absolute values but rather become essential in comparative investigations when assessing the influences of alloying elements at a fundamental level,that is,free electron density distributions.Our study indicated that the principles of‘electronic metallurgy'in developing multi-elemental alloy systems can be followed via practical experimental methods,i.e.ΔWF measurements using KPFM and nanoindentation.

A theoretical investigation of the band alignment of type-I direct band gap dilute nitride phosphide alloy of GaN_xAs_yP_(1-x-y)/GaP quantum wells on GaP substrates

The GaP-based dilute nitride direct band gap material Ga（NAsP） is gaining importance due to the monolithic integra- tion of laser diodes on Si microprocessors. The major advantage of this newly proposed laser material system is the small lattice mismatch between GaP and Si. However, the large threshold current density of these promising laser diodes on Si substrates shows that the carrier leakage plays an important role in Ga（NAsP）/GaP QW lasers. Therefore, it is necessary to investigate the band alignment in this laser material system. In this paper, we present a theoretical investigation to optimize the band alignment of type-I direct band gap GaNxAsyP1-x-y/GaP QWs on GaP substrates. We examine the effect of nitrogen （N） concentration on the band offset ratios and band offset energies. We also provide a comparison of the band alignment of type-I direct band gap GaNxAsyP1-x-y/GaP QWs with that of the GaNxAsyP1-x-y/Al2Ga1-2P QWs on GaP substrates. Our theoretical calculations indicate that the incorporations of N into the well and AI into the barrier improve the band alignment compared to that of the GaAsP/GaP QW laser heterostructures.

Nonlinear Theory on Dynamic Controlling Interface Patterns DuringSolidification of a Dilute Binary Alloy

In non-equilibrium nonlinear region, the nonlinear equations of time dependence of perturbation amplitude at the solid/liquidinterface during solidification of a dilute binary alloy are established on the base of assuming that there is local equilibrium at the solid/liquid interface and considering that curvature, temperature and composition at the solid/liquid interface which are related to the perturbation amplitude are nonlinear. As a result, patterns at the solid/liquid interface during solidification process, which is from nonsteadystate to steady state can be controlled by these nonlinear equations.

Valence electron structures dependences of structural stability and properties of REX_(3)(RE=rare earth;X=In,Tl)and RE(In,Co)_(3) alloys

Intermetallic compounds REIn_(3)(RE=rare earth)have attracted much attention due to their unique characteristics:crystal field effect,Kondo effect,superconductivity,heavy fermion,and antiferromagnetism,and their cobalt diluted alloys exhibit the ferromagnetic half-metallic characteristics at room temperature.In this study,an empirical electron theory(EET)is employed to investigate systemically the valence electronic structure,the thermal and magnetic properties of REX_(3) and their cobalt diluted alloys for revealing the mechanism of physical properties.The calculated bond length,melting point,and magnetic moment match the experimental ones very well.The study reveals that structural stability and physical properties of REX_(3) and their cobalt dilute alloys are strongly related to their valence electron structures.It is suggested that the structural stability and cohesive energy depend upon the covalent electron,the melting point is modulated by covalent electron pair,and the magnetic moment is originated from 3d magnetic electron.The ferromagnetic characteristics of Co-diluted REIn3 alloys is originated from the introduction of strong ferromagnetic Co atom,but,a competition is caused between the electron transition from valence electron to magnetic electron on d orbit and its reversal electron transformation with increasing the content of cobalt,which results in the formations of diluted magnetic Gd(In,Co)_(3) alloy with minor amount of cobalt and strong magnetic Nd(In,Co)_(3) alloy with doping more Co atoms.

Magnetic phase diagrams of Fe–Mn–Al alloy on the Bethe lattice

The magnetic behaviors of the Fe–Mn–Al alloy are simulated on the Bethe lattice by using a trimodal random bilinear exchange interaction（J） distribution in the Blume–Capel（BC） model. Ferromagnetic（J 〉 0） or antiferromagnetic（J 〈 0）bonds or dilution of the bonds（J = 0） are assumed between the atoms with some probabilities. It is found that the secondor the first-order phase boundaries separate the ferromagnetic（F）, antiferromagnetic（AF）, paramagnetic（P）, or spin-glass（SG） phases from the possible other one. In addition to the tricritical points, the special points at which the second- and the first-order and the spin-glass phase lines meet are also found. Very rich phase diagrams in agreement with the literature are obtained.

Study on removal of nitrate nitrogen by Iron-Silver Alloy

With the rapid development of industry,a large number of wastewater discharged from factory production leads to a gradual increase in nitrate content in natural water.Using iron-silver copper alloy as reactant and catalyst can effectively reduce the content of nitrate nitrogen in wastewater.The experimental results show that the loading rate of silver is 3% and pH is 2 at room temperature.The maximum removal rate of nitrate nitrogen is 91.09%.

7075铝合金表面制备AlSi_(10)Mg涂层

以AlSi_(10)Mg合金粉末为熔覆材料,在7075铝合金基体上进行单层单道激光熔覆实验,研究激光功率、扫描速率、送粉率对熔覆层成形的影响规律,以阐述稀释率较高和气孔率较低现象产生的原因。结果表明:随着激光功率的增加,熔覆层宽度增大、高度减小;当激光功率增加到一定程度后,增加送粉率会使熔覆层的宽度和高度显著增大;而送粉率较低时,扫描速率对熔覆层宽度和高度的影响较小。激光功率较高时,基材和粉末熔合充分,产生的气泡较少;同时,送粉率较低时,熔覆层的高度较低,更利于气泡从熔池中逸出,熔覆层气孔率降低至0.07%。因此,在较高激光功率搭配较低送粉率的工艺下会形成高度较低的熔覆层,整体稀释率较高。此结果为降低铝合金激光熔覆气孔缺陷提供一定的指导意义。

激光熔覆不同层数FeCoNiCr_(0.5)Al_(0.2)高熵合金涂层的组织与性能

目的研究不同层数高熵合金涂层的耐磨性和耐腐蚀性。方法采用激光熔覆技术在Q345钢表面制备FeCoNiCr_(0.5)Al_(0.2)高熵合金涂层。采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、摩擦磨损试验机等研究高熵合金涂层的组织结构,并表征其性能。结果高熵合金涂层与基体Q345钢实现了良好的冶金结合。当涂层大于3层时,稀释率达到理想区间,涂层表面主要由细小的等轴晶和柱状组织组成。随着涂层层数的增加,相结构逐渐转变为FCC相,涂层表面Fe的原子数分数从66.72%降至30.46%,稀释率由37.7%降至9.8%。1层涂层的硬度最高,达到422HV0.5,约为基体的3.5倍;当涂层层数大于3时,表面的平均硬度为190HV0.5左右,是基体的1.5倍左右。在空气中,涂层相较于基体,在10、20 N载荷下磨损率分别下降了23.3%~37.1%、8.4%~21.0%。在质量分数3.5%的NaCl溶液中,涂层相较于基体,在10、20 N载荷下磨损率分别下降了38.4%~45.5%、43.9%~47.7%。在10、20 N载荷下,涂层在空气中的磨损率分别是在质量分数3.5%的NaCl溶液中的6倍、4.5倍左右。与基体相比,1、3、5层涂层的腐蚀电位分别提升了11.9%、57.6%、50.2%,腐蚀电流密度下降了1~2个数量级。结论随着高熵合金涂层层数的增加,稀释率降低,硬度提高,耐磨性和耐腐蚀性大幅提升,根据不同的性能需求可以灵活选择制备不同层数的涂层。

Efect of Al Content on the Corrosion Behavior of Extruded Dilute Mg–Al–Ca–Mn Alloy

The microstructure,extrusion texture and corrosion behavior of extruded dilute Mg–Al–Ca–Mn alloy with diferent Al contents were investigated.The corrosion rate of the alloy was more sensitive to the Fe impurities.The 1.2 wt%Al showed the lowest corrosion rate,which was mainly attributed to the weakening of the cathode efect caused by the increase of the Al and the decrease of the Fe in the precipitated phase.Refned grains,stronger basal surface texture and higher corrosion potential deriving from the higher Al content of the matrix also further enhanced the corrosion resistance of the matrix.

稀盐酸对铸造镁合金回炉料混料判定的影响

在铸造镁合金熔炼过程中添加回炉料时,用稀盐酸滴在回炉料锯切的光洁面上,可根据合金表面与稀盐酸反应时不同的反应现象区分铸造镁合金材料牌号。有效识别回炉料成分,防止发生混料、造成成本浪费。

电感耦合等离子体原子发射光谱法测定镍合金中的钼含量

本文详细报告了质量稀释校准法的“电感耦合等离子体原子发射光谱法测定镍合金中的钼含量的分析方法研究”试验工作。通过样品溶解试验、称样量试验、基体干扰试验、内标元素选择试验等优化和确立了分析方法条件,建立了电感耦合等离子体原子发射光谱发测定镍合金中钼含量的分析方法。精密度试验、标样测试、方法比对、加标回收等试验表明所建立的方法是准确可靠的,满足了镍合金中钼含量的测定要求。本方法改进了ISO 11435:2011标准,将钼的测定上限从20%提高到30.00%,方法适应性更广,可推荐作为国家标准。

激光功率对球阀表面激光熔覆Co基合金涂层稀释率及耐腐蚀性能的影响

采用CO2激光器在阀门材料316不锈钢表面激光熔覆了Co基合金涂层。借助扫描电镜、能谱仪和电化学综合测试仪等,探讨了激光功率对涂层稀释率、微观组织及耐腐蚀性能的影响。结果表明:激光功率越大,涂层稀释率越大,熔覆层与基体元素有较多的对流与扩散;熔覆层的耐腐蚀性能随激光功率的增加先提高后降低,当激光功率为2.1k W时,熔覆层的自腐蚀电位最低,为-0.8456 m V,当激光功率为1.8 k W时,熔覆层的腐蚀电流密度最小(3.4152×10-7A·cm-2)。

S271低合金钢堆焊镍基合金稀释率影响因素研究

针对核电站用S271低合金钢上堆焊690镍基合金,研究焊接速度、送丝速度和焊接电流对单层单道焊稀释率的影响。结果表明,焊缝稀释率与其均有关。当焊接电流与焊接速度一定时,稀释率随送丝速度增大而降低;当焊接电流和送丝速度一定时,稀释率随焊接速度的增加而增加;当焊接速度和送丝速度一定时,稀释率随焊接电流的增大而增大。但是在热输入一定和焊接电流电压保持不变的情况下,改变送丝速度与焊接速度几乎不影响焊缝稀释率。

同位素稀释质谱法测定铀铌合金中铀含量

根据同位素稀释质谱法原理,推导了铀铌合金中铀含量的计算公式。研究了铀铌合金的分解方法,优化了取样量和稀释剂用量,探讨了质谱谱线干扰和合金元素干扰对测量结果的影响。加入硝酸和氢氟酸定量溶解铀铌合金,再定量加入铀同位素稀释剂,直接制备成混合试样溶液,应用质谱法测定混合溶液、铀铌合金试样的铀同位素比,最后计算出铀铌合金中铀含量。确定的方法无需定量分离铀。为了对分析结果的准确性进行验证,应用XRF法、ICP-AES法和元素分析法测量铀铌合金中铌含量和杂质元素总量,反推得到相应的铀含量,其结果同实验方法的结果是一致的。对铀铌合金样品进行分析,测定结果的相对标准不确定度为0.2%(6次测定),扩展不确定度为0.5%(95%置信水平)。

司太立合金等离子弧堆焊工艺参数对焊层稀释率的影响

采用正交试验方法,分析了等离子弧堆焊主要工艺参数对司太立合金堆焊层稀释率的影响,采用光学显微镜观察了堆焊层的组织,并用硬度计测试了堆焊层的硬度。结果表明,等离子弧堆焊工艺参数中对堆焊层稀释率影响程度按大小排序依次为送粉量、转移弧电流及堆焊速度。最优参数为送粉量31 g/min,转移弧电流142 A,堆焊速度151 mm/min,在此工艺参数下试焊得到的堆焊层稀释率为2.2%,堆焊层组织为胞状和树枝状的α-Co基固溶体加枝晶间的碳化物,表面硬度达到HV440左右。

温度场监控下高功率半导体激光熔敷钴基合金涂层

采用3.5 kW半导体激光器在42CrMo4表面熔覆了钴基合金(Stellite 6)涂层,利用光学显微镜和显微硬度仪表征了涂层的微观组织和硬度分布,研究了监控熔覆过程中的熔池温度场对涂层的微观结构和显微硬度的影响。结果表明:基于熔池温度场拍摄并调整激光器输出功率的熔池大小闭环监控的工艺可实现对钴基合金涂层的稀释率以及结构与性能的调控;当送粉量为22.6 g/min、熔覆速率为1 m/min时,基于熔池温度场监控的工艺调整实现了近零稀释率的钴基合金涂层的熔覆,所需激光功率仅为1.5 kW;涂层与基体形成良好的冶金结合,组织致密,主要由平面晶、胞状晶、树枝晶和等轴晶构成,晶粒细小,显微硬度达到HV600。

脱模剂稀释用水对镁合金压铸件质量的影响

通过采用不同的脱模剂稀释用水,研究了水质对镁合金压铸件质量的影响。结果表明:在脱模剂稀释用水中加入一定浓度的钙离子,对压铸产品成形有利,产品质量好;但钙离子加入量过少时脱模剂附着性差,过多时则影响镁液流动性。纯水+CaCl2的稀释水使用方便,而且合格率高,质量稳定性好,可用于批量生产,且对后面工序无影响。

面向泵阀的钴基合金激光熔覆层组织与性能特征

目的改善泵阀密封面质量,延长其使用寿命和提高泵阀使用可靠性。方法在已做单道涂层预实验基础上,采用大功率光纤耦合半导体激光器于泵阀材料ZG45平板上制备多道钴基合金熔覆层。利用光学显微镜(OM)、扫描电子显微镜(SEM)、X射线衍射仪(XRD)、能谱仪(EDS)、显微硬度计、盐雾腐蚀箱等实验测试仪器,分析熔覆层组织形态特征、成分、显微硬度及腐蚀行为,确定多道钴基涂层的工艺参数及性能。结果多道钴基熔覆层存在可行的工艺参数,熔覆层致密,且与基材形成冶金结合。涂层显微组织主要由柱状晶、胞状晶、柱状树枝晶及枝间共晶组织组成,主要相为γ-Co、Cr23C6。枝晶中心主要由Co和Fe元素组成,其含量从枝晶中心向周围区域递减。枝晶间化合物主要由Cr、C、W元素组成,其含量均匀分布于枝晶间。涂层的平均显微硬度为586.5HV0.3,是基体的2.8倍以上,显微硬度随着稀释率的降低而增加。熔覆层的耐盐雾性能显著提高。结论基于钴基合金的表面激光熔覆技术可以有效地提高其硬度和耐腐蚀性,可用于泵阀密封面的表面性能强化。

新型Al-Ti-B-RE中间合金细化工业纯铝的研究

采用颗粒纯钛法制备新型的Al-Ti-B-RE中间合金,为提高铝制品的质量和降低成本,在稀释熔融状态下对工业纯铝进行细化处理。借助于扫描电镜(SEM)、光学显微镜(OM)等手段对其晶粒细化效果进行分析对比。细化实验表明,稀释后Al-Ti-B-RE中间合金在较短的时间内就具有较好的晶粒细化效果,要优于的AlTiB中间合金。