Effects of Zr Additions on the Microstructure and Impression Creep Behavior of AZ91 Magnesium Alloy

The effects of 0.2, 0.6, and 1.0 wt pct Zr additions on the microstructure and creep behavior of AZ91 Mg alloy were investigated by impression tests carried out under constant punching stress (σ _imp) in the range 100 to 650 MPa, corresponding to the modulus-compensated stress levels of 0.007 ￡ s_\textimp \mathord

Interfacial Phase in Ti-5Al-2Mo-3Zr Alloy

Under appropriate cooling condition, intcrfacial phase appeared between α and β phases in Ti-5Al-2M0-3Zr alloy. Its thickness could reach 100 nm. The interfacial phase was either single layer structure or double layer structure. The monolithic layer adjacent to 3 phase was indentified as fee structure with relationship （110）_β// （001）_m, [11$\\mathop 1\\limits^{{\\rm{ - - }}} $]_β /[110]_m. The striated layer adjacent to a phase was indentified as hep with twin relationship {10$\\bar 1$1}<1$\\bar 0$12> to α. Thus, the study provided a new experimental fact for the controversial topic on structure of striated layer. Chemical composition of interfacial phase varied slightly with heat treatments, but always between that of α and β phases.     

铁铬铝合金裂纹产生时的声发射

通过声发射及扫描电镜技术,研究了铁铬铝合金裂纹形成的条件。结果表明,合金中热应力可产生微裂纹;内应力的存在以及环境氢的渗入,通常使盘条产生纵向裂纹;合金的失效过程是一个通过声发射释放能量的过程。     

超声波振动对Al-8.0%Cu合金抗裂性的影响

以Al-Cu合金为原材料,研究超声波对Al-8.0%Cu合金热裂倾向性的影响。结果表明,金属熔体经过超声波处理后,合金的抗裂力增大,热裂倾向明显降低,断口为沿晶断裂并且存在明显的液膜拉伸痕迹。     

Ti-5A1-2Mo-3Zr合金的低温形变

对Ti-523合金由室温到-75℃之间的拉伸性能和形变行为作了系统研究,发现淬火态在-75℃拉伸仍保持高塑性,而经回火的试样则塑性较低。两者的强度在低温下均升高,可比室温强度高10%。形变机理则由室温的滑移为主变为低温下的以孪生为主,交替温度可能在-15℃~-30℃之间。低温形变出现一种双重\     

铸态和沉积态Al-25Si-5Fe-3Cu合金的显微组织与相形成

采用常规铸造和喷射成形工艺制备了含硅达25%(质量分数)的过共晶Al-Si合金,利用SEM(EDS)、XRD和DSC等分析方法对合金的显微组织和相熔解析出进行了分析研究.结果表明,铸态合金含有粗大块状初晶Si相和粗大针片状含铁相,而喷射成形工艺能够使二者的尺寸、形貌发生改变而有利于合金性能的提高.同时,铸态和沉积态合金中均含有基体Al、初晶Si和Al₂Cu相,不同的是铸态合金中含铁相主要为δ-Al₄FeSi₂相,而沉积态合金中以β-Al₅FeSi相为主.分析其原因主要是糊状层的存在引起沉积坯冷却速度降低而导致沉积坯中发生δ-Al₄FeSi₂相的转变及共晶组织增加,致使沉积态合金中β-Al₅FeSi相为主要含铁相.采用DSC实验对沉积态合金在熔化和凝固过程中发生的反应进行了讨论.     

喷射沉积Al-20Si-5Fe-3Cu-1Mg合金的微观组织与力学性能

利用喷射沉积技术制备了Al-20Si-5Fe-3Cu-1Mg合金,借助扫描电镜(SEM),X-射线衍射和拉伸试验等手段研究了喷射沉积合金的微观组织和力学性能,分析了Fe对合金挤压和热处理后的组织变化.拉伸试验结果表明,喷射沉积Al-20Si-5Fe-3Cu-1Mg合金具有比粉末冶金Al-20Si-3Cu-1Mg合金更高的高温(300℃)强度.     

Effect of Scandium on Corrosion Resistance of Welded Joint of Al-6Mg-Zr Alloy

Al Mgalloyshavebeenwidelyusedinmanyin dustries,especiallyinmarineandaircraftapplica tions,duetotheirgoodweldability,ductilityandex cellentcorrosionresistance.Beingthenon heattreat ablealloys,thesematerialsderivetheirstrengthpri marilyfromsolidsolutio…     

Si对Fe-25Cr合金高温硫化行为的影响

本文研究了少量Si(1.5%、2.5%)对Fe-25Cr合金在H₂S-H₂混合气氛中高温硫化行为的影响。在800℃以上加Si一定程度地提高了Fe-25Cr合金的抗硫化性能。由于硫化过程中硫化层发生开裂,使得含Si合金有些硫化增重曲线的规律性较差。含Si合金生成了比较完整、均匀的(Cr、Fe)₂S₃内硫化层,但保护作用不大。在对硫化动力学曲线、硫化层结构和组成分析的基础上探讨了Fe-25Cr-xSi合金的硫化机理及Si元素的作用。     

Influence of Laser Treatment on the Creep of the Ti-6Al-4V Alloy

Titanium and its alloys are excellent materials for structural applications in components submitted to high temperatures because of their high strength, weight ratio, good corrosion resistance, and microstructural stability. However, the affinity to oxygen is one of the main factors that limit their application as structural materials at high temperatures. The objective of this work was to estimate the influence of laser treatment on the creep of a Ti-6Al-4V alloy. Constant load creep tests were conducted at 873 K (600 °C) in a standard creep machine at a stress of 125 to 319 MPa. Samples with a gage length of 18.5 mm and a diameter of 3.0 mm were used for all tests. It was observed that the effect of the oxidation was smaller and the behavior of the creep curves showed that the life time in laser treated samples was better than in the received samples. An increase of ductility of final strain and in the lifetime for the laser-treated material was observed. The decrease of the steady-state creep occurred in conjunction with the oxidation process reduction, showing that for the Ti-6Al-4V alloy, the lifetime is affected strongly by the laser treatment with an increase in this superficial protection.     

Creep and rupture properties of an austenitic Fe-30Mn-9Al-1C alloy

The creep deformation behavior and rupture properties of as-quenched austenitic Fe-30Mn-9Al-1C alloy have been studied at 923, 948, and 973 K under applied stresses ranging from 50 to 350 MPa. The creep curves of the alloy exhibited an extended tertiary stage prior to failure. The stress and temperature dependencies of the minimum creep rate indicated two regimes of creep deformation as well as a transition from creep to power-law breakdown. These two regimes of creep deformation were identified as a low-stress creep regime having an activation energy of 140 kJ/mol and a stress exponent of about 1, and a power-law creep regime having an activation energy of 350 kJ/mol and a stress exponent of about 6. Transmission electron microscope (TEM) observations of the deformed specimens revealed that a low density of dislocations, coarse dislocation networks, and profuse slip bands were developed in the low stress, power law, and power-law breakdown regimes, respectively. Optical microscope and scanning electron microscope (SEM) observations of the ruptured specimens showed that creep cavitation shifted from round-type in the low-stress creep regime to wedge-type in the power-law breakdown regime. The observed creep and rupture characteristics of the alloy are interpreted in terms of creep mechanisms, which involve the Coble creep and dislocation climb creep.     

微量Nd和Sc对Al-6.5 Mg-0.5Mn 合金组织及力学性能的影响

采用拉伸力学性能测试、扫描电镜及透射电镜观察等手段研究了微量Nd和Sc对Al-6.5Mg-0.5Mn合金的显微组织及力学性能的影响.结果表明:分别单独添加Nd, Sc使合金的抗拉强度均有所提高;同时添加Nd和Sc可使合金的抗拉强度、屈服强度分别提高65 MPa、55MPa,但合金的伸长率有所降低;合金中晶界上形成含Nd或Sc的化合物,这些化合物钉扎亚晶界、从而抑制合金的再结晶晶粒的形成.     

Effect of Yttrium Additions in Relation to Oxygen Content on Glass Formation in the Zr50Cu40Al10 Alloy

Metallurgical and Materials Transactions A - The effect of yttrium additions on the glass formation of the Zr50Cu40Al10 alloy with high oxygen content was investigated. Unlike other reports showing...     

Creep behavior of Ti-25Al-10Nb-3V-1Mo

A study has been made of the role of microstracture in room-temperature tensile properties as well as elevated-temperature creep behavior of an advanced Ti₃Al-base alloy, Ti-25Al-10Nb-3V-lMo (atomic percent). Creep studies have been performed on this alloy as a function of stress and temperature between 650 °C and 870 °C, since the use of conventional titanium alloys has generally been restricted to temperatures below 600 °C. A pronounced influence of microstructure on creep resistance was found. Generally, the β solution-treated colony-type (slow-cooled or SC) microstructure showed superior creep resistance. This improved creep resistance in β/SC is accompanied by lower room-temperature tensile strength and ductility. Study of the stress dependence of steady-state creep rate indicates that increasing temperature caused a gradual decrease in the stress exponentn and a transition in creep mechanism at 870 °C, depending on applied stress level. Transmission electron microscopy observations of deformed dislocation structures developed during steady-state creep and room-temperature tensile tests, as well as the corresponding fracture modes, were used to interpret properties as a function of temperature. Finally, creep behavior of the present Ti₃Al alloy was found to be superior to that of conventional near-α titanium alloys. WONSUK CHO, formerly with Carnegie Mellon University, is Senior Research Staff Member, Kia Technical Center, Yeoeuido, P.O. Box 560, Seoul, Korea. JAMES WILLIAMS, formerly Dean of Engineering, Carnegie Mellon University.     

Cr对改善低合金钢抗CO2腐蚀性能的影响

研究了不同Cr含量的低合金钢在模拟不同油田CO2腐蚀环境下的抗CO2腐蚀性能,并对Cr元素改善钢的抗CO2腐蚀行为及机理进行了分析.     

锻造对喷射成形Al-8.5Fe-1.3V-1.7Si合金组织和性能的影响

采用喷射成形和锻造工艺制备了Al-8.5Fe-1.3V-1.7Si合金．通过金相、扫描电镜和力学性能测试等实验，对锻件组织和性能进行了分析。结果表明：“闷车＋包套锻造”工艺对喷射成形Al-8.5Fe-1.3V-1.7Si合金坯件的致密化效果好于用自由锻造和包套锻造致密化的合金，采用该工艺可以制备出组织和性能优良的耐热铝合金材料。“闷车＋包套锻造”锻件在室温下的抗拉强度（σb）达到407MPa，屈服强度（σ0.2）达到344MPa，延伸率（δ5）为7．6％；在315℃，锻件的σb，σ0.2，σ5分别为222，216MPa，7．2％。     

离心转速对过共晶铝硅合金Al-19Si-5Mg组织的影响

通过改变离心铸造的转速,获得了内层聚集大量Mg2Si和初晶Si,中层不含Mg2Si和初晶Si,外层含有少量Mg2Si和初晶Si的Al-19％Si-5％Mg合金自生梯度功能复合材料圆筒形零件,分析了该复合材料零件组织分布特征和成型工艺过程及影响因素。实验结果表明：离心转速将明显影响第二相颗粒的分布;离心转速越高,颗粒的偏聚越明显。