Structural Features of Cast Refractory Alloy HP40NbTi High-Temperature Oxidation. Part I. Evolution of Microstructure and Phase Composition

Metal Science and Heat Treatment - Optical and electron microscopy, x-ray spectral microanalysis, and thermogravimetric analysis in combination with differential scanning calorimetry are used to...     

Kinetics of the High-Temperature Oxidation of Heat-Resistant Statically and Centrifugally Cast HP40NbTi Alloys

Oxidation of Metals - The high-temperature oxidation kinetics at 800 to 1200 °C of as-cast heat-resistant HP40NbTi alloys produced by either static or centrifugal casting were studied...     

High-Temperature Oxidation Behavior of Refractory High-Entropy Alloys: Effect of Alloy Composition

The high-temperature oxidation behavior of a new family of refractory high-entropy alloys (HEAs) with compositions of W–Mo–Cr–Ti–Al, Nb–Mo–Cr–Ti–Al and Ta–Mo–Cr–Ti–Al was studied at 1000 and 1100 °C. Based on these equimolar starting compositions, the main incentive of this study was to select the most promising alloy system whose properties may then be successively improved. Despite the high amount of refractory elements, Ta–Mo–Cr–Ti–Al showed good oxidation resistance at 1000 and 1100 °C. Moderate values of mass gain and complex oxidation kinetics were observed for the W- and Nb-containing HEAs. These alloys formed inhomogeneous oxide scales possessing regions with thick and porous layers as well as areas revealing quite thin oxide scales due to the formation of discontinuous Cr- and Al-rich scales. The most promising behavior was shown by the alloy Ta–Mo–Cr–Ti–Al which followed the parabolic rate law for oxide growth due to the formation of a thin and compact Al-rich layer.     

Effect of G-Phase on the Fracture Behavior of a Welded Joint from Refractory Alloy HP40NbTi

Metal Science and Heat Treatment - The microstructure, the phase composition and the mechanical properties at 20°C and 870°C of a tubular welded joint from alloy HP40NbTi based on the Fe...     

Al对HP40合金显微组织的影响

试验中用中频无芯感应炉熔炼、树脂砂型制备出HP40、加Al5%～10%降Ni5%～10%的合金试样,用Mef3光学金相显微镜观察金相组织,用EPMA-1600电子探针分析组织中各元素的分布,结合D8ADVANCE型X射线衍射确定合金中的相组成。结果表明,随铝含量增加,合金基体从γ相转变为α相;析出相除碳化物外,还生成了FeNiAl金属间化合物强化相,并随铝含量的增多进一步增多、长大,形状由片条状逐步转变成羽毛状。     

钛硅系铸造合金的微观组织演变

研究了钛硅系铸造合金的相组成、微观组织。X射线衍射试验表明,随着硅含量的增加,Ti5Si3相（ζ）的衍射峰越来越明显。同时,合金由固溶体的片状或网蓝片组织逐渐演变为典型的棒状共晶组织。结果表明,钛硅系铸造合金与传统的铸造钛合金有着截然不同的微观组织特征。     

Ti40阻燃钛合金的高温氧化行为

研究了高稳定β型阻燃钛合金Ti40合金在900℃-1050℃温区内氧化时的氧化行为。结果表明：随着温度的升高及时间的延长，试样表面氧化皮由较为平整变化为表面氧化皮严重脱落且基体表面呈现为淡绿色。对该物质进行能谱分析后显示淡绿色物质为TiO2和Cr2O3的混合物。900℃～1000℃的氧化动力学曲线显示，随温度升高氧化增重急剧增加，在温度1000℃～1050℃范围内，试样氧化增重虽仍随时间的增加而增加，但总量有所下降。     

快淬SmFe合金的微观结构及相组成

采用SEM、XRD、EDX、AFM等方法分析了快淬Sm-Fe合金的微观结构和相组成。研究表明：Sm-Fe合金铸锭由Sm2Fe17相、富Sm相和大量的α-Fe相组成，经过一定的均匀化热处理后，获得了几乎单一的Sm2Fe17相合金；快淬速度为10m／s时，获得的Sm-Fe合金由Th2zn17，菱形对称结构的Sm2Fe17相及少量的α-Fe组成，合金晶粒尺寸约为100nm，且分布不均匀：当快淬速度为20m／s时，合金仍由Sm2Fe17相和α-Fe相组成，但与10m／s的合金相比，α-Fe相明显增多，同时稳定相Sm2Fe17向亚稳定相Sm10Fe90转变；当快淬速度大于30m／s时，合金完全为ThCu7型六角晶结构的Sm10Fe90相，平均晶粒尺寸在40～50nm，分布均匀。     

Surface Oxidation and Subsurface Microstructure Evolution of Alloy 690TT Induced by Partial Slip Fretting Corrosion in High-Temperature Pure Water

The surface oxidation and subsurface microstructure evolution of Alloy 690 TT can occur during partial slip fretting corrosion in high-temperature pure water.Detailed characterization methods such as laser scanning confocal microscopy,scanning electron microscopy,electron probe micro-analyzer,and transmission electron microscopy were used to reveal the related mechanism.The results showed that Cr_2 O_3 oxides together with a small number of spinel oxides were formed in sticking region since a small quantity of high-temperature water could pass through the gaps between the asperities to oxidize the materials.Widespread distribution of oxides in microslip region consisted of(Ni,Fe)Cr_2 O_4,because Ni~(2+) and Fe~(2+) ions could react with Cr_2 O_3 to generate a small amount of non-stoichiometric spinel oxides.The oxides around micropitting in microslip region consisted of double-layer structure.The outermost layer contained(Fe,Cr)-rich oxides due to the effect of fretting leading to mechanical mixing between Cr_2 O_3 and(Ni,Fe)(Fe,Cr)_2 O_(4.)The inner layer consisted of(Fe,Ni)-rich oxides owing to the consumption of Cr_2 O_3 by the reaction with Ni~(2+) and Fe~(2+) ions.The reciprocating motion of oxide particles in microslip region resulted in the stress-strain supporting the recrystallization for the formation and development of a tribologically transformed structure in subsurface and plowing effect by fretting in surface.     

热处理对加Al改性HP40合金组织的影响

通过光学显微镜和电子探针研究了热处理对含铝(质量分数)5%～10%的HP40合金组织的影响。结果表明:选择合适的热处理工艺,能使铸态合金中的沉淀相均匀析出;当固溶温度较高时,可观察到析出相非常均匀且尺寸较小。在1220℃及其以上温度固溶处理时,合金中的沉淀相才能完全固溶于基体。     

Some Features of High-Temperature Oxidation of Aluminide Coatings on Alloy TsNK-7P

Special features of high-temperature oxidation of aluminide coatings (slip-deposited Al – Si and ion-plasma-deposited VSDP-11) on alloy TsNK-7P are considered. The kinetics of the oxidation process, the element composition, and the microhardness of coatings with different thicknesses are described. Results of thermal fatigue tests of alloy TsNK-7P with aluminide diffusion coatings are presented. It is shown that the VSDP-11 coating ensures a higher heat resistance and thermal fatigue strength on alloy TsNK-7P than the Al – Si coating and can replace the latter on turbine vanes of gas compressor units.     

高温空气氧化作用下低铝含量FeCrAl涂层的组织演变（英文）

通过磁控溅射技术在Zr-4合金基体上沉积了厚度约为18μm的FeCrAl涂层,以提高Zr合金的高温抗氧化性能。通过空气氧化实验研究了低Al含量的FeCrAl涂层抗氧化性能。为了评估涂层界面演变和元素迁移之间的关系,采用了场发射扫描电子显微镜、能谱仪和掠入射X射线衍射仪进行了深入分析。结果表明,尽管FeCrAl涂层在1000℃空气氧化后会出现分层剥落,但该涂层仍然有效地保护了Zr-4合金基体不被氧化。FeCrAl涂层性能下降的主要原因是高温下Al元素严重向外扩散以及Fe、Cr元素向内扩散,最终导致涂层内部分层和剥落。此外,还讨论了FeCrAl涂层在800、900和1000℃时的空气氧化行为。     

快速凝固Gd5Si2Ge2合金的显微组织与相组成

研究了在真空电弧炉和快淬炉2种快速凝固条件下制备的Gd5Si2Ge2合金的显微组织与相组成。结果表明，Gd5Si2Ge2合金亿电弧炉熔炼条件下，具有不同质蟹的样品可以获得不同的显微组织与相组成。不同速度下，快淬甩带实验表明，在小于40m／s的快淬速度下，Gd5Si2Ge2合金为单斜Gd5Si2Ge2-型晶体结构：在50m／s的快淬速度下Gd5Si2Ge2合金包含Gd5Si4-型和Gd5Si2Ge2-型两相。证实了冷却速度对Gd5Si2Ge2合金的相组成有重要影响。