ZrO2对钼铼合金微观组织与性能的影响

钼铼合金具有优良的力学性能和机加工性能,是电子、核工业等领域关键的结构材料。在钼铼合金中加入氧化锆,形成弥散强化作用,并结合形变强化来提高材料的力学性能。研究发现,合金粉粒度随着ZrO₂含量的增加而减小,在含量为0.7%时晶粒尺寸最细小均匀;ZrO₂颗粒在合金的变形和断裂过程中表现出钉扎效应,显著提升合金的抗拉强度、屈服强度和断后延伸率等力学性能;ZrO₂强化钼铼合金的抗拉强度和断后延伸率在ZrO₂含量为0.7%时达到最高值,随后减少;ZrO₂基本弥散分布在晶界处并与钼基体形成良好结合界面,可以抑制晶界的迁移,提高钼合金的变形抗力。     

La2O3对MGH956合金TIG焊焊缝组织和性能的影响

为了研究La₂O₃对焊缝组织和性能的影响,分别以未填加、填加2%和4%La₂O₃的填充材料对MGH956合金进行TIG焊接,应用光学显微镜、扫描电镜和透射电镜对焊缝的微观组织和拉伸断口进行观察,同时测试焊缝的抗拉强度.结果表明,适当提高La₂O₃含量,可以使焊缝晶粒得到细化,填加2%La₂O₃的焊缝晶粒最细小均匀,焊缝中的颗粒相增多且分布均匀,强化机制是由细晶强化和Orowan强化共同作用,但当La₂O₃加入量达到4%时,发现颗粒相有团聚现象,强化主要由位错塞积引起.填加2%La₂O₃的焊缝抗拉强度最大,为628 MPa,拉伸断口为韧-脆混合断裂.     

Al0.7Sb2Te3三元靶材的结构性能表征

以原子比Al:Sb:Te=0.7:2:3的混和粉为原料,采用真空合成法与烧结-热等静压制备Al_0.7Sb₂Te₃三元靶材,通过XRD、FESEM、EDS、XPS等手段表征其性能,且重点采用XPS研究Al在Al_0.7Sb₂Te₃三元靶材的存在状态。结果表明：Al掺杂后,靶材主相Sb₂Te₃的晶格常数减小,且单质Al弥散相与Al_0.1Sb₂Te₃基体相共存,表明掺杂对靶材的组织结构确有影响;刻蚀深度从0增加至405.9nm,Al价态从以Al₂O₃的化合态为主逐渐过渡至以单质态为主,且Al以Al₂O₃形态为主的区域深度约90nm;刻蚀深度为405.9nm时,来自非氧化物的Al价态与来自AlSb的Sb价态联合表明：Al_0.1Sb₂Te₃中的Al通过有效化合形成AlSb影响着靶材的组织结构。     

纳米Y2O3对高Nb-TiAl合金高温蠕变性能的影响

在不同温度、不同应力条件下对高Nb-TiAl合金进行蠕变测试,结合扫描电子显微镜(SEM)、透射电子显微镜(TEM)等分析手段探究纳米Y₂O₃对Ti-45Al-6Nb-2.5V合金高温蠕变性能的影响。铸态高Nb-TiAl合金组织为α₂/γ层片结构,纳米Y₂O₃的添加可显著细化合金组织并改善合金的高温拉伸性能。蠕变结果分析得出,添加0.15at.%纳米Y₂O₃会显著改善Ti-45Al-6Nb-2.5V合金的抗蠕变性能,在800℃/300MPa条件下,合金稳态蠕变速率由2.389×10^_-7s^_-1降至1.500×10^_-7s^_-1;在850℃/250MPa条件下,合金的蠕变寿命由14.10h延长至61.50h。添加纳米Y₂O₃提高合金蠕变抗力的机制是Y₂O₃与基体具有较高的结合强度,可以有效阻碍位错运动,减弱孔洞萌生的倾向。经分析,两种合金在800℃/300MPa下的蠕变行为主要受位错攀移与孪晶控制,蠕变损伤断裂机理为孔洞萌生与裂纹扩展。     

高压凝固Al2O3/Al-10Si复合材料组织热稳定性及力学性能研究

本文采用高压凝固的方法分别在3、4、5 GPa的压力下制备了Al₂O₃/Al-10Si复合材料,并分别在160 ℃保温2、4、6 h的条件下研究了高压凝固Al₂O₃/Al-10Si复合材料的组织热稳定性以及力学性能转变规律。研究表明：热处理导致高压凝固Al₂O₃/Al-10Si复合材料α相固溶的Si在热激活的作用下脱溶析出,聚集长大形成细小颗粒弥散分布于α相内,形成沉淀强化;160 ℃热处理后α相固溶的Si析出,过饱和程度下降,材料性能逐渐趋于稳定,在沉淀强化的共同作用下,Al₂O₃/Al-10Si复合材料抗压强度和压缩率较热处理前均有所上升。而160℃保温4 h的条件下,材料的综合力学性能最好。尤其在5 GPa压力下凝固的Al₂O₃/Al-10Si复合材料,抗压强度可达到716 MPa。     

La2O3含量对Al2O3/Cu基复合材料组织与性能的影响

以La₂O₃粉、Al粉、CuO粉为反应物原料、纯铜为基体,采用原位合成技术和近熔点铸造法制备颗粒增强Cu基复合材料,研究La₂O₃对Al-CuO体系制备的Cu基复合材料组织及性能的影响。结果表明：添加La₂O₃可获得纳米Al₂O₃颗粒,且弥散分布于Cu基体中,制备的材料组织更加细小、均匀,其材料的电导率及摩擦磨损性能明显提高。当添加0.6%wtLa₂O₃,复合材料的电导率达到90.2%IACS,磨损量达到最小,相比未添加La₂O₃,其导电率提高10.1%,磨损量减小36.6%。     

离子注入法在316L不锈钢基体上制备Al2O3 阻氚涂层

采用离子注入技术在316L不锈钢基体上制备了氧化铝阻氚涂层。对离子注入法的不同工艺参数对α-Al₂O₃涂层摩擦磨损、耐腐蚀、抗热震、阻氚性能的影响进行了研究。结果表明：温度、加速电压及离子注入剂量对α-Al₂O₃的含量均有影响。温度升高时, α-Al₂O₃的含量增加。增大加速电压及离子注入剂量时,α-Al₂O₃含量均出现先升高后降低的规律。离子注入剂量对涂层的摩擦磨损、耐腐蚀性能影响比较大：离子注入剂量越大,涂层的耐磨、耐腐蚀性能越好。涂层经过200次热震测试后未发生变化,抗热震性能较好。Al₂O₃膜层具有优异的阻氚性能,在600 ℃下能使316L不锈钢的氚渗透率降低3个数量级。     

γ-TiAl合金表面Al2O3/Al复合涂层的抗高温熔盐腐蚀性能研究

采用磁控溅射技术于γ-TiAl合金表面制备Al₂O₃/Al复合涂层。在850 °C下、 100 wt.% Na₂SO₄熔盐中观测Al₂O₃/Al复合涂层的高温腐蚀行为。结果表明,Al₂O₃/Al复合涂层具备由Al₂O₃表层、富Al中间层以及互扩散层组成的梯度结构,因而有效地提高了基体γ-TiAl合金的抗高温腐蚀性能。在腐蚀实验后,涂层试样表面相结构为Al₂O₃,TiO₂和TiAl₃。致密的Al₂O₃/Al复合涂层有效地抑制了O_2-,S_-和Na₊对基体γ-TiAl合金的侵蚀。并且,Al₂O₃/Al复合涂层的梯度结构亦使其表现出了优异的抗开裂和抗剥落性能。     

超音速微粒沉积-激光同步强化Inconel718涂层高温氧化行为

针对镍基高温合金 Inconel 718 表面损伤问题,利用超音速微粒沉积-激光同步强化技术在基体表面制备了相同成分的 Inconel 718 修复涂层。 采用场发射扫描电子显微镜( SEM) 及其自带的能谱分析仪 EDS、X-射线衍射仪 (XRD)、显微拉曼光谱仪、场发射高分辨透射电子显微镜(TEM)分析了激光功率为 1300 W 时涂层的微观组织结构和 750 ℃高温氧化后表/ 截面形貌。 结果表明:涂层表面光洁,内部组织致密,孔隙率仅为 0. 2%,涂层与基体结合良好且无明显裂纹等缺陷。 在氧化初期,镍基高温合金涂层表面快速氧化并形成富 Ni、Fe、Cr 的 NiO、Fe₂O₃ 、Cr₂O₃ 以及含 Ni 的尖晶石 Cr₂O₃·NiO 结构。随着氧化时间的延长,NiO 与 Fe₂O₃ 结合生成复合相 NiFe₂O₄ ,而覆盖在 NiO 表面的 Cr₂O₃ 不断生长扩张,与 NiO 发生固相反应生成 NiCr₂O₄ 。     

放电等离子烧结WMoNbTaV-Al2O3 高熵合金组织及磨损性能

以金属粉末为原料,采用放电等离子烧结技术制备新型含α-Al₂O₃的WMoNbTaV难熔高熵合金,研究了烧结温度对合金致密化行为、相结构、显微组织和耐磨性能的影响。结果表明：在1800~1900 ℃烧结时,WMoNbTaV-Al₂O₃高熵合金基体具有单一bcc相结构,Al₂O₃的平均晶粒尺寸为1.15 μm。随着烧结温度升高,合金的晶粒尺寸增大,致密度和显微硬度也在不断增高,在1900 ℃烧结时硬度达到7967.4 MPa。1900 ℃烧结得到的合金具有优异的耐磨性,磨损量仅为1800 ℃烧结合金的一半。且WMoNbTaV-Al₂O₃高熵合金的耐磨性远高于纯W材料。当磨料粒度为37.5 μm时,1900 ℃烧结的合金磨损量为0.9 mg,磨损性能是纯W材料的83倍。     

Influence of minor additions on the emissivity of the oxide scale of FeCrAlY alloys during resistance heating

Chromium aluminum yttrium (FeCrAlY) alloys owe their low oxidation rate to the formation of a slow growing α‐alumina scale. For material used for heating elements not only the life time and the behavior of the resistance during the life time is of relevance, but also the emission coefficient of the oxide scale. The power density J_S produced by resistance heating of strip with 50 µm thickness and about 5–6 mm width at 1050 °C is approximately equal to the radiant flux density, which is according to Stefan–Boltzmann's law proportional to the total emission coefficient ε_g. Resistance heating tests were performed on samples made from FeCrAlY alloys with different zirconium and carbon content. The “high zirconium” containing FeCrAlY alloys (zirconium > about 0.10%) have a higher power density/emissivity than the “low zirconium” alloys. In parallel with this, all samples with higher power density/emissivity have internal oxidation and therefore a “rough” metal–oxide interface. Thus, one cause for the increase of the emissivity of the scale could be this rough metal–oxide interface; other causes could be a higher amount of zirconium incorporated into the scale, more pores and/or different grain structure in the scale. Additionally the carbon content influences the appearance of a higher emissivity and the internal oxidation.     

CEMS studies of structural modifications of metallic glasses by ion bombardment

Fe₇₆Mo₈Cu₁B₁₅ and Fe₇₄Nb₃Cu₁Si₁₆B₆ amorphous metallic alloys were exposed to ion bombardment with nitrogen ions and protons to ensure different degree of radiation damage. The radiation damage profiles were calculated in the “full cascade” mode. Conversion electron Mössbauer spectrometry was employed to scan structural modifications in the surface regions of the irradiated alloys. In Fe₇₆Mo₈Cu₁B₁₅, the irradiation with 130 keV N⁺ has caused a significant increase of the hyperfine magnetic fields and isomer shift due to changes in topological and chemical short-range order (SRO), respectively. No appreciable effects were revealed after bombardment with 80 keV H⁺ ions. Fe₇₄Nb₃Cu₁Si₁₆B₆ amorphous metallic alloy was irradiated by 110 keV N⁺ and 37 keV H⁺ and only changes in chemical SRO were revealed after bombardment with nitrogen ions. The observed alternations of the structure depend primarily on the total number of displacements of the resonant atoms which are closely related to the fluence as well as type and energy of the incident ions.     

Corrosion behavior of Zr–Nb–Cr cladding alloys

Zr-Nb-Cr alloys were used to evaluate the effects of alloying elements Nb and Cr on corrosion behavior of zirconium alloys. The microstructures of both Zr substrates and oxide films formed on zirconium alloys were characterized. Corrosion tests reveal that the corro- sion resistance of ZrxNb0.1Cr （x = 0.2, 0.5, 0.8, 1.1; wt%） alloys is first improved and then decreased with the increase of the Nb content. The best corrosion resistance can be obtained when the Nb concentration in the Zr matrix is nearly at the equilibrium solution, which is closely responsible for the formation of columnar oxide grains with protective characteristics. The Cr addition degrades the corrosion resistance of the Zrl.lNb alloy, which is ascribed to Zr（Cr,Fe,Nb）2 precipitates with a much larger size than β-Nb.     

Surface modification by carbon ion implantation for the application of ni-based amorphous alloys as bipolar plate in proton exchange membrane fuel cells

Ni-based amorphous alloys with surface modification by carbon ion implantation are proposed as an alternative bipolar plate material for polymer electrolyte membrane fuel cells (PEMFCs). Both Ni₆₀Nb₂₀Ti₁₀Zr₁₀ alloys with and without carbon ion implantation have corrosion resistance as good as graphite as well as much lower contact resistance than 316L stainless steel in the PEMFC environment. The formation of conductive surface carbide due to carbon ion implantation results in a decrease in the contact resistance to a level comparable to that of graphite. This combination of excellent properties indicates that carbon ion implanted Ni-based amorphous alloys can be potential candidate materials for bipolar plates in PEMFCs.     

Potentialities of Mössbauer Spectroscopy for Studying Zirconium Alloys and Their Oxide Films

A brief review and an analysis of results of a study of iron- and tin-bearing zirconium alloys and their oxide films by the method of Mössbauer spectroscopy (MS) are presented. The potentialities of MS for studying the phase composition of zirconium alloys are described and the changes in the states of iron and tin atoms are presented as a function of additional alloying and thermomechanical treatment. The conditions of formation of Zr₂Fe and Zr₃Fe intermetallic compounds and chromium- and niobium-bearing compounds are considered. It is shown that some intermetallic compounds transform into other compounds at room temperature. Metallic iron and tin are shown to be present in oxide films of zirconium alloys, and their concentration is shown to affect the corrosion resistance of zirconium alloys.     

Untersuchung über das Korrosionsverhalten von Zirkoniumlegierungen. IV. Das Lochfraßverhalten Zirkoniumlegierungen

Investigation into corrosion behaviour of zirconium alloys. IV-Pitting behaviour of zirconium alloys Electrochemical investigations into the resistance of a number of Zr-alloys in different solutions against pitting corrosion have shown that additions of Va- and VIa-group metals and in particular Ti improve the resistance of pure Zr. Metals forming local elements decrease pitting corrosion resistance. Minor amounts of Fe, Ni and Cr have practically no influence. The pitting corrosion resistance of Zr and its alloys decreases with increasing concentration of chloride ions in the solutions. Additions of SO₄-ions retard the beginning of the pitting but do not shift the pitting corrosion potential. NO₃-ions on the other hand produce a real inhibition. Newly developed methods for the quick determination of the pitting corrosion potential were very useful for the described investigations.     

ODS2铁素体合金抗辐照损伤性能

利用电子辐照,离子辐照等多种辐照模拟方法,对机械合金化方法制备的弥散强化铁素体２合金抗辐射损伤性能进行了研究。实验表明：在抗辐照肿胀和抗辐照偏析方面,所研制的材料明显优于对照实验的氏体合金;积分通量１．７×１０＾１７／ｃｍ＾２氩离子注入,引起表层起泡,龟裂,劣于对照材料,辐照后韧脆转变温度高于Ｆｅ－１３％Ｃｒ合金。存在轧制造成的强度各向异性问题。材料韧性有待提高。     

Tetragonal phase stability in ZrO2 film formed on zirconium alloys and its effects on corrosion resistance

A thermodynamic model is developed to understand the origin of variation in the microstructure of ZrO₂ film formed on zirconium alloys and its effects on corrosion resistance. The correlation among the tetragonal phase fraction, the stress (macroscopic and internal one), the ZrO₂ grain size and the microstructural change of oxide film is formulized, and then analyzed. The results show that many complicated factors simultaneously govern the microstructure of oxide film. The tetragonal phase content near the oxide/metal interface, the macroscopic compressive stress near the interface, the decline gradient of macroscopic compressive stress and the internal stress induced by the transformation from the tetragonal to the monoclinic phase have very important influences on the transition from columnar grains to equiaxed grains, the crack formation and the degradation of oxidation resistance. The presence of intermetallic precipitates in oxide film may effectively relax the internal stress caused by transformation strain, stabilize the columnar-grain structure and reduce the probability of crack formation. How to reduce the transformation stress in the oxide film is a key to improve the corrosion resistance of zirconium alloys.     

The thermal oxidation of ion-implanted zirconium

The thermal oxidation of polycrystalline zirconium implanted with 21 different ion species has been studied by using the nuclear reaction ¹⁶O(d, p₁)¹⁷O.A very good agreement has been found between the oxidation kinetics of unimplanted zirconium as determined by the nuclear reaction and those previously measured gravimetrically. Oxidation kinetics show a time dependence which is cubic or parabolic depending upon the surface treatment before oxidation. Ion implantation produces significant changes in oxidation rate but the time dependence remains the same. A strong correlation has been found between the behaviour of ion implanted systems and that reported for binary alloys, confirming the hypothesis that the ionic size of the additive is the major parameter governing the influence upon the oxidation of zirconium. The implanted species which inhibit oxidation possess ionic radii lying between 80% and 100% of that of Zr⁴⁺. An explanation of their beneficial effect based on an increase of the plasticity of the growing oxide is presented.     

Metal dusting of nickel-base alloys

Metal dusting, the disintegration of metallic materials into fine metal particles and graphite was studied on nickel, Fe Ni alloys and commercial Ni-base alloys in CO H₂ H₂O mixtures at temperatures between 450–750°C. At carbon activities a_c > 1 all metals can be destroyed into which carbon ingress is possible, high nickel alloys directly by graphite growth into and in the material, steels via the intermediate formation of instable carbide M₃C. Protection is possible only by preventing carbon ingress. Chromium oxide formation is the best way of protection which is favoured by a high chromium concentration of the alloy and by a surface treatment which generates fast diffusion paths for the supply of chromium to the surface. The metal dusting behaviour of Alloy 600 is described in detail. A ranking of the metal dusting resistance of different commercial nickel-base alloys was obtained by exposures at 650°C and 750°C.