微量元素B、Zr对镍高温合金组织结构与高温力学性能的影响

通过扫描电镜研究了在Ni-20Cr-10Mo-10Co合金中分别添加微量元素B、Zr后，合金的组织结构的变化。并且对在实验条件为800℃、170MPa情况下的合金蠕变和持久性能进行了测试，结果均有明显提高。     

铬对FeNiMoCu系预合金粉末烧结性能的影响

将Cr以铬铁的形式加入到FeNiMoCu系预合金粉末中,经充分混合后单轴600MPa下压制,然后分别采用冷压烧结、烧结热锻和复烧工艺,研究铬对FeNiMoCu系预合金粉末烧结密度、组织及性能的影响.实验结果表明,添加到预合金粉末中的铬在1573K温度烧结时可均匀扩散到组织中,使组织性能得到改善;随添加的铬量和复烧温度的提高,微观组织硬度和表观硬度逐渐增加,经热锻及热锻复烧可获得较高的烧结密度和硬度.当复烧温度为1573K时,Fe-1.5Cr-2.0Ni-0.85Mo-1.7Cu-0.5C获得的密度为7.71 g/cm3,硬度为105HRB;Fe-4.0Cr-3.0Ni-0.85Mo-1.7Cu-0.5C获得的密度为7.63g/cm3,硬度为105HRB.     

Al含量对Fe-22Cr-25Ni含铝奥氏体耐热钢高温抗氧化性能的影响

以HR3C合金成分为基础,通过调控Cr、Ni含量和添加1.5%,2.5%和3.5% (质量分数) 的Al制备了Fe-22Cr-25Ni型含铝奥氏体耐热钢,并研究了合金的高温抗氧化性能。利用SEM、EDS和XRD对含铝奥氏体钢700、800和900 ℃氧化后的氧化膜组成、结构进行了表征。结果表明：22Cr-25Ni-2.5Al和22Cr-25Ni-3.5Al含铝奥氏体耐热钢在700和800 ℃下具有优异的抗高温氧化性能。氧化后表层形成了连续致密的Al₂O₃保护膜,提高了其高温抗氧化性能。3种耐热钢经900 ℃氧化时形成外层为Cr₂O₃和MnCr₂O₄的复合氧化层,且氧化层下存在Al₂O₃内氧化物和AlN析出相,不能对基体起到有效保护作用。     

SPS制备Ti-18Mo-xSi合金的高温氧化行为研究

采用高能球磨-放电等离子烧结技术制备了Ti-18Mo、Ti-18Mo-0.5Si、Ti-18Mo-1Si和Ti-18Mo-2Si4种合金,研究了Si含量对合金微观结构、相组成的影响及700和800℃空气中合金的氧化行为。结果表明:烧结合金中主要由Ti(Mo)固溶体组成,添加Si元素合金出现了Mo_5Si_3相。在700和800℃空气中分别氧化100 h后,合金表面主要有TiO_2、Ti O、MoO_2和MoO_3相,添加Si元素的合金氧化后还出现了SiO_2相。4种合金在700℃下的氧化增重明显小于800℃下的氧化增重,Ti-18Mo-0.5Si合金在700和800℃下平均氧化速率分别为0.09和0.10 g·(m~2·h)~(-1),其抗氧化性明显优于其他合金。     

N型热电偶及其在陶瓷磨具生产中的应用

N型热电偶是一种新型廉金属热电偶,正极为镍铬硅(Ni-14.2Cr-1.4Si),负极为镍硅合金(Ni-4.4Si-0.1Mg)。具有比常用的K型电偶更好的抗氧化性与稳定性。众所周知,K型热电偶因其一系列优点而广为使用。但是它在800℃以上使用时合金的内氧化导致     

反复镦拔对Ni-20Cr-11Co-8Mo-4W合金组织和性能的影响

研究了反复镦拔工艺对Ni-20Cr-11Co-8Mo-4W合金组织和力学性能的影响。对Ni-20Cr-11Co-8Mo-4W合金反复镦拔前后的径向微观组织进行了金相、扫描电镜观察和分析,并对试验合金反复镦拔前后的室温冲击断口形貌进行了观察和分析。研究结果表明,采用反复镦拔工艺可以明显改善Ni-20Cr-11Co-8Mo-4W合金的微观组织,从而提高合金的力学性能。     

组织结构对Ni—20Cr—10Mo—10Co高温合金高温力学性能的影响

Ni-20Cr-10Mo-10Co高温合金是一种以碳化物为主要强化相的铸造高温合金。合金的晶粒尺寸和枝晶间距，随着模壳温度的降低而减小，在使用温度为800℃时合金中碳化物的类型发生变化。另外，实验发现随着模壳温度的降低，合金在800℃，165MPa时的持久寿命和蠕变性能都得到改善，持久拉伸试样为穿妥理断口，表明这种材料的等强温度在800℃以上，所以晶粒、枝晶的细化有利于高温力学性能的提高。     

过热器管用Ni基合金的强度特性

据日刊报道,日本开发的在500℃/9.8MPa蒸气条件下使用的JHN-24(Ni-20Cr-18Mo)过热器管,经在锅炉中使用验证,其与现用的含高Cr、Mo的Ni基合金HastelloyC-22(HC-22)都具有耐高温性能。随后对这两个合金的固溶状态、等温后的组织和强度特性等进行了研究。试验材的成分分别为:JHN-24Ni-19.8Cr-17.3Mo-2.6Fe-0.7Nb-0.19Hf-0.002C;HC-22Ni-21.3Cr-13.1Mo-3.0W-4.0Fe-0.003C。其试样为Φ38mm×8mm无缝管和12mm钢板。用固溶状态样做常温和高温拉伸试验、冲击试验。在400~550℃温度下,JHN-24试验材保温10000h,HC-22材保温3000h,然后…     

Al、Si及Y多元合金化对Cr-20Nb合金高温氧化行为的影响

针对软第二相Cr稍微降低Laves相NbCr2合金的1200℃抗氧化性,采用Al、Si及Y多元合金化来提高Cr-20Nb合金的高温抗氧化性能。结果表明,多元合金化的Cr-20Nb合金1100℃及1200℃抗氧化性均好于加入单一合金化的及纯Cr-20Nb合金,并随着Si合金元素含量增加,Cr-20Nb合金的氧化增重变小,抗氧化性变好;SEM结果表明,添加合金元素后,氧化膜与基体的粘附性得到了明显提高。     

NiAl(Ti)-Cr(Mo)共晶合金的微观组织和力学性能

Ni-32Al-28Cr-3Mo-4Ti(原子分数,％)共晶合金组织由β-NiAl和α-Cr(Mo)共晶组成,并含有少量初生β-NiAl相和Ni_2AlTi相．合金压缩屈服强度超过稀土Dy合金化的NiAl-Cr(Mo)合金,与NiAl-28Cr-5Mo-1Hf合金相当,表明Ti合金化有利于提高NiAl-Cr(Mo)共晶合金的强度．合金在1000℃下的蠕变断裂寿命和最小蠕变速率均与施加载荷之间呈线性的双对数关系,蠕变断裂寿命与最小蠕变速率之间满足Monkman-Grant关系修正式：t_f·((?)min)~(0.71)=0．51．合金的室温断裂方式为共晶相的解理断裂以及NiAl与Cr(Mo)相界面的剥离,高温蠕变断裂由共晶胞界处微空洞形成和聚集所导致．     

Comparison of geometries and electronic structures of polyacetylene,polyborole, polycyclopentadiene,polypyrrole, polyfuran,polysilole, polyphosphole,polythiophene, polyselenophene and polytellurophene

Geometries of monomers through hexamers of cylopentadiene, pyrrole, furan, silole, phosphole, thiophene, selenophene and tellurophene, and monomers through nonamers of borole were optimized employing density functional theory with a slightly modified B3P86 hybrid functional. Bandgaps and bandwidths were obtained by extrapolating the appropriate energy levels of trimers through hexamers (hexamers through nonamers for borole) to infinity. Bandgaps increase with increasing π-donor strengths of the heteroatom. In general, second period heteroatoms lead to larger bandgaps than their higher period analogs. Polyborole is predicted to have a very small or no energy gap between the occupied and the unoccupied π-levels. Due to its electron deficient nature polyborole differs significantly from the other polymers. It has a quinoid structure and a large electron affinity. The bandgaps of heterocycles with weak donors (CH₂, SiH₂ and PH) are close to that of polyacetylene. For polyphosphole this is due to the pyramidal geometry at the phosphorous which prevents interaction of the phosphorus lone pair with the π-system. The bandgap of polypyrrole is the largest of all polymers studied. This can be attributed to the large π-donor strength of nitrogen. Polythiophene has the third largest bandgap. The valence bandwidths differ considerably for the various polymers since the avoided crossing between the flat HOMO — 1 band and the wide HOMO band occurs at different positions. The widths of the wide HOMO bands are similar for all systems studied. All of the polymers studied have strongly delecalized π-systems.     

Supplemental Literature Review of Binary Phase Diagrams: Cd-Se, Cu-Hg, Cu-Ho, Eu-Mg, H-Sr, Hf-Si, La-Mn, Mn-Nd, Nb-Y, Ni-Y, Pb-Se, and Sc-Sr

Recent literature on Cd-Se, Cu-Hg, Cu-Ho, Eu-Mg, H-Sr, Hf-Si, La-Mn, Mn-Nd, Nb-Y, Ni-Y, Pb-Se, and Sc-Sr phase diagrams is reviewed in this article in order to update the 1990 compilation Binary Alloy Phase Diagrams, 2nd edition, by T.B. Massalski, et al. For some systems reaction tables and crystal structure data have been included, as well. Diagrams have been checked for consistency with rules for phase diagram construction and modified when necessary. In addition, diagrams needing more work have been identified.     

Supplemental Literature Review of Binary Phase Diagrams: Cs-In, Cs-K, Cs-Rb, Eu-In, Ho-Mn, K-Rb, Li-Mg, Mg-Nd, Mg-Zn, Mn-Sm, O-Sb, and Si-Sr

Recent literature on Cs-In, Cs-K, Cs-Rb, Eu-In, Ho-Mn, K-Rb, Li-Mg, Mg-Nd, Mg-Zn, Mn-Sm, O-Sb, and Si-Sr phase diagrams is reviewed in this article in order to update the 1990 compilation Binary Alloy Phase Diagrams, 2nd edition, by T.B. Massalski, et al. For some systems reaction tables and crystal structure data have been included, as well. Diagrams have been checked for consistency with rules for phase diagram construction and modified when necessary. In addition, diagrams needing more work have been identified.