Effect of coating repair on microstructure and mechanical properties of Ni3Al based alloy IC6

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Effect of high temperature aging on microstructure and mechanical properties of a directionally solidified Ni3Al base alloy IC6A

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Repair of NiCrAlYSi overlay coating on Ni3Al base alloy IC6

The effect of repair of NiCrAlYSi coating after long time use on the coherence of coating to substrate and mechanical properties of Ni₃Al base alloy IC6 has been studied. The alloy with NiCrAlYSi coating was stressed under the condition of 900 °C/100 MPa for 200 h to simulate the service condition of IC6 turbine vanes. The results showed that the coherence of base alloy/original coating, original coating/first repair coating, first repair coating/second repair coating or base alloy/second repair coating was firm. The interfaces between them had no cracks and porosity, for either partly or entirely repaired coatings. However, there were more Mo rich particles in the affected zone compared with original coating. Compared with IC6 alloy aged at 900 °C for 200 h, the yield strength at ambient temperature of IC6 alloy with first repair coating was almost equivalent, while the elongation decreased slightly; its stress rupture life under 1100 °C/90 MPa condition was about 100 h. For secondary coating repair, the room temperature tensile properties of base alloy had no obvious change, while stress rupture lives decreased, but still were rather long, compared to the alloy with first repair coating. Therefore, NiCrAlYSi coating repair is feasible to prolong the service lives of IC6 turbine vanes.     

Y对Mg-8Li-3Al合金组织和性能的影响

采用真空感应熔炼技术制备了Mg-8Li-3Al-xY（x=0.5,1.0,3.0）合金。研究稀土Y对Mg-8Li-3Al合金组织和性能的影响。结果表明：在Mg-8Li-3Al合金中加入稀土Y,α（Mg）相被明显细化和球化,合金中生成了Al2Y相,添加w（Y）=0.5%-1%后,合金强度得到提高。     

Effects of yttrium on microstructure and mechanical properties of Mg-6Al magnesium alloy

Since Y has a great solid solubility in magnesium alloys, it helps enhancing the heat-resistant property of magnesium alloys. The effects of Y on microstructures and mechanical properties of Mg-6Al alloy have been studied in this work. The results show that Y addition refines grains of Mg-6Al alloy, and reduces the amount of the Mg 17 Al 12 phase. At the same time, the high melting-point Al 2 Y phase particles are formed. According to the mathematical model of the two-dimensional lattice misfit proposed by Braffit, it is believed that the Al 2 Y particles can serve as the nucleation sites for α-Mg. After T6 treatment, both elongation and ultimate tensile strength of Mg-6Al alloy at the room temperature and high-temperature increased firstly and then decreased, with increasing Y addition. The peak mechanical properties were achieved in the Mg-6Al-1.2Y alloy system. Y addition appears to change the fracture characteristic of Mg-6Al alloy. With 1.2wt%Y, the fracture surface of the alloy showed a lot of dimples and tearing ridges which connected the microscopic dimples and the fracture is mixed fracture of quasi-cleavage and ductile fracture.     

Influence of solution heat treatment on microstructure and stress rupture properties of a Ni3Al base single crystal superalloy IC6SX

The effect of solution heat treatment at different temperatures on the microstructure and stress rupture properties of a Ni₃Al base single crystal superalloy IC6SX has been investigated in this paper. The experimental results show that the as-cast alloy exhibited a typical dendritic structure with three phases of γ′, γ and NiMo. After solution heat treated at 1240 °C, the NiMo phase dissolved entirely. With the temperature increasing, the γ′ phase in interdendritic region dissolved earlier than that in dendritic region. When solution heat treatment temperature reached to 1280 °C, all of the γ′ solutioned and a uniform microstructure was observed. Furthermore, increasing the temperature up to 1340 °C, a small amount of incipient melting occurred in the alloy. The stress rupture life of IC6SX at 1100 °C/130 MPa increased with the rising of temperature and reached to the top value under the solution heat treatment temperature of 1280 °C. The optimum solution heat treatment considered to be 1280 °C/10 h followed by flowing air cooling.     

Isothermal solidification behavior of typical Ni_3Al base superalloy IC6

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Ni3Al基合金IC6及MCrAlY包覆涂层的抗腐蚀性能

采用离子电弧镀的方法在Ni3Al基合金IC6上涂覆了NiCrAlY，NiCoCrAlY及NiCoCrAlYHf3种MCrAlX涂层，测试了IC6合金及其涂层900℃时的抗热腐蚀性能。利用电子探针、SEM、X射线等手段观察了腐蚀试样的微观结构，分析了腐蚀产物的组成，探讨了IC6合金及其涂层的腐蚀机理。结果表明：3种涂层均使IC6合金的抗热腐蚀性能有明显改善，NiCoCrAlYHf涂层的效果最为显著，表面氧化膜的酸性溶解是造成热腐蚀的主要原因。     

Al含量对Ni3Al基IC10合金凝固行为的影响

研究Ni3Al基合金IC10两种不同Al含量合金中初生相的析出温度及析出顺序,确定了两种合金在不同等温温度下固-液两相比例变化。结果表明,低铝合金中(γ+γ′)共晶析出温度比高铝合金下降了20℃,液相线温度提高了5℃,并且失去枝晶间毛细补缩能力温度与固相线之间的温度范围明显缩小,失去枝晶间补缩区的液相量F明显减少,从而使低铝合金浇铸叶片时的热裂倾向降低,合金的可铸性提高。     

Effect of yttrium on the microstructure of a semi-solid A356 Al alloy

The semi-solid slurry of an A356 Al alloy,which was grain-freed by yttrium,was manufactured by low temperature pouring.The effects of grain-refining on the morphology and the grain size of the primary α phase in the semi-solid A356 Al alloy were researched.The results indicate that the semi-solid A356 Al alloy with particle-like and rosette-like primary α-Al can be prepared by low temperature pouring from a liquid grain-refined A356 alloy.The grain size and particle morphology of primary α-Al in the A356 Al alloy are markedly improved by the addition of 0.5 wt.% Y.The fining mechanism of Y on the morphology and grain size of the primary α-Al in the semi-solid A356 Al alloy was delved.     

Effect of anisotropy on microstructure and high temperature stress rupture properties of Ni3A1 base single crystal alloy

The effect of anisotropy on microstructure and high temperature stress rupture property of Ni3A1 base single crystal alloy was investigated. The single crystal specimens were produced by screw selection crystal method. The microstructures were examined by OM, SEM, TEM and X-ray EDS techniques. The stress rupture tests were can-led out in air by constant load creep machines under 1 100 ℃ and 130 MPa. The experimental results show that the dendrites preferential orientation deviates certain angles to heat flow orientation, and the secondary arms occur for different crystallographic orientations. The single crystal alloy with different orientations shows obvious anisotropy during tensile stress rupture tests under 1 100 ℃ and 130 MPa. The 〈111〉 orientation specimen has the best stress rupture life of 211 h. The high ductility at 1 100 ℃ of the 〈001〉 orientation specimen may be attributed to the most multiple equivalent slip systems.     

Y对AZ91D镁合金铸态组织和性能的影响

通过金相分析、扫描电镜分析及拉伸性能测试等手段,研究了Y的添加对AZ91D镁合金的微观组织和力学性能的影响.结果表明,加入适量的Y后,合金的第二相由粗大的网状变成细小的颗粒状,合金的力学性能得到了改善.当Y的实际含量达到0.48%时,合金组织中第二相的细化程度最大;其抗拉强度和延伸率达到最高.     

Effect of yttrium coating on the oxidation behavior of Ni3Al

Yttrium-coated Ni₃Al with post heat treatment has shown good high-temperature oxidation resistance. To understand the effect of the Y-coating and post heat treatment on the oxidation resistance of Ni₃Al, the specimens were coated with Y by an ion-plating method, and heat treatment was performed at low oxygen level before or after the Y-coating was applied. Performance of the Y-coated Ni₃Al was evaluated by isothermal and cyclic oxidation tests. A simple deposition of Y on Ni₃Al did not change the oxidation kinetics, but the post heat treatment after Y-ion plating significantly decreased the oxidation rate of Ni₃Al. The scale formed on Y-coated Ni₃Al with post heat treatment after Y-ion plating showed a fine and dense structure which was grain refined by the presence of a (Y, Al) O-type oxide in the scale. The coated Y layer becomes a Y-Al compound during heat treatment. The presence of the (Y, Al)O-type oxide in grain boundaries or the lattice of Al₂O₃ modify the diffusion rate of Al and oxygen, and the oxide microstructure during oxidation. Improvement of cyclic-oxidation resistance of Ni₃Al by the Y-coating occurs because the presence of (Y, Al)O-type oxide develops fine-grain oxides which can easily relieve the growth stress.     

深冷处理对Cu-3Ti-5Ni合金组织与性能的影响

采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)及高分辨率透射电子显微镜(HRTEM)对Cu-3Ti-5Ni合金深冷处理前后的组织演化及析出相进行了表征分析,采用维氏硬度计、涡流电导仪分别分析了深冷处理对合金硬度和导电率的影响。结果表明,Cu-3Ti-5Ni合金经深冷处理后,析出细小颗粒相,Ni3Ti第二相析出更完全。TEM分析发现深冷处理后针状Ni3Ti析出相的周围出现了位错的缠绕,基体中的位错线向位错环转换。适当时间的深冷处理可有效提高Cu-3Ti-5Ni合金的硬度,经深冷处理15 h后合金硬度达最大值217 HV10,但深冷处理对合金导电率的影响甚微。     

含钇Mg-6Al镁合金组织和高温力学性能

研究了稀土元素Y(0～2.4wt%)对Mg-6Al合金显微组织和力学性能的影响.结果表明,添加稀土元素Y可以显著提高时效态合金从室温至200℃区间的拉伸屈服强度和抗拉强度.在Mg-6Al合金中加入0.6wt%～2.4wt%的Y后,合金的显微组织均得到细化,Al2Y高熔点点状稀土合金相产生.在本研究的范围内,加入1.2wt%Y的合金从组织到性能各项性能最优.     

Sn对Mg-8.5Li-3Al合金组织和性能的影响

采用真空感应熔炼技术制备了Mg-8.5Li-3Al和Mg-8.5Li-3Al-1Sn合金,研究Sn对Mg-8.5Li-3Ai合金组织和性能的影响,结果表明,Sn在Mg-Li-Al系合金中主要以颗粒状Mg2Sn化合物的形式存在于β(Li)相中,Mg2Sn颗粒对Mg-Li-Al合金可以起到第二相强化作用.     

Al3Ti3B中间合金对AZ91D镁合金组织及力学性能的影响

研究了Al3Ti3B中间合金对AZ91D镁合金显微组织及力学性能的影响.通过光学显微镜和扫描电子显微镜观察发现,Al3Ti3B中间合金能显著减小AZ91D合金的二次枝晶臂间距与晶粒尺寸,在加入0.3%Al3Ti3B时晶粒尺寸就由原来的约260 μm减小至约100μm.伴随着合金晶粒尺寸的减小,合金的抗拉强度、屈服强度和延伸率都明显提高,这主要是由于晶粒细化后能阻碍裂纹扩展的有效晶界增多,晶界强化作用显著;同时,Al3Ti3B中间合金的加入促使溶质均匀分布,使共晶体(α Mg17Al12)形貌发生改变,共晶体尺寸减小,这有利于裂纹切过脆性的共晶体传播,提高合金的变形协调能力.     

Microstructure and mechanical properties of Mg-6Al magnesium alloy with yttrium and neodymium

The effects of rare earth (RE) elements Y and Nd on the microstructure and mechanical properties of Mg-6Al magnesium alloy were investigated. The results show that a proper level of RE elements can obviously refine the microstructure of Mg-6Al magnesium alloys, reduce the quantity of/β-Mg17Al12 phase and form Al2Y and AI2Nd phases. The combined addition of Y and Nd dramatically enhances the tensile strength of the alloys in the temperature range of 20-175℃. When the content of RE elements is up to 1.8%, the values of tensile strength at room temperature and at 150℃ simultaneously reach their maximum of 253 MPa and 196 MPa, respectively.The main mechanisms of enhancement in the mechanical properties of Mg-6Al alloy with Y and Nd are the grain refining strengthening and the dispersion strengthening.     

稀土钇对Pt-5Ru合金组织结构和性能的影响

用真空电弧熔炼方法制备Pt-5Ru合金,并添加少量钇进行弥散强化。用X射线衍射仪(XRD)、金相显微镜、显微硬度仪和分光光度计等设备研究了Pt-Ru-Y合金的显微组织结构、力学性能和反射率的变化。结果表明,稀土元素钇的添加可以对Pt-Ru合金晶粒起到显著的细化作用,减少合金内部缺陷,提高合金的显微硬度,使合金力学性能得到明显的改善。