V-Ti-Fe三元合金显微组织、氢传输行为及耐蚀性能研究

Nb-Ti-Fe双相合金已被证实具有优异的渗氢性能,有望成为替代传统Pd膜的渗氢材料。V和Nb同属于5B族,具有类似的物理化学性质,但是,V-Ti-Fe双相合金组织转变规律和渗氢性能至今无人研究。基于此,本工作对V-Ti-Fe三元合金的显微组织和渗氢行为开展了详细研究,并探索了热处理和电化学腐蚀对改善渗氢性能的可能性。研究结果表明:V-Ti-Fe三元合金体系中存在一个包共晶凝固反应,即L+TiFe_(2)→Bcc-(V,Ti)+TiFe(1626 K)。液相面投影图中存在三个相区,分别为TiFe相区、TiFe_(2)相区和Bcc-(V,Ti)相区。其中,TiFe相区合金室温组织由初生TiFe相和{Bcc-(V,Ti)+TiFe}共晶结构组成,TiFe_(2)相区合金室温组织由初生TiFe相、TiFe_(2)相和Bcc-(V,Ti)相构成,Bcc-(V,Ti)相区合金室温组织由初生Bcc-(V,Ti)相和TiFe相组成,渗氢性能测试证实了该系合金抗氢脆性能较弱。具体来说,上述三区域内部铸态合金在渗氢实验前均发生了不同程度的破碎,仅V_(2.5)Ti_(62.5)Fe_(35)合金能够渗氢,不过,该合金在渗氢后期发生断裂。最后,本工作采用电化学腐蚀和真空热处理两种方法改善该合金体系的渗氢性能,其中,V_(2.5)Ti_(62.5)Fe_(35)合金具有较高的耐腐蚀性能,经热处理后该合金的渗氢性能明显提升,其在623 K下的氢渗透性能为1.03×10^(-9)mol H_(2)m^(-1)·s^(-1)·Pa^(-0.5)。

电弧熔炼Fe-V合金的凝固组织与转变规律研究

采用电弧熔炼法制备不同成分的Fe-V合金材料,并采用扫描电子显微镜、背散射电子显微镜、硬度计检测等对其铸态和热处理条件下的微观组织和力学性能进行表征分析。结果表明:Fe-V合金铸态组织共存在3种相:基体固溶体α相、亚稳相α'相及脆硬相σ相。慢速升温淬火会使Fe-V合金组织内部以及生成的σ相长大,使从基体分离出的α'相发生溶解;快速升温淬火,Fe-V合金组织内部已经生成的σ相没有明显长大,还变得细小。富铁部分Fe-V合金淬火条件下硬度比铸态组织要低,相反富钒部分合金硬度升高。

电感耦合等离子体原子发射光谱法检测钛合金中Fe、Al、V含量

建立了电感耦合等离子体原子发射光谱仪(ICP-AES)检测钛合金中铁(Fe)、铝(Al)、钒(V)含量的方法。采用氢氟酸(1+1)进行溶解。经测定,3种元素在0~60 mg/L范围内呈线性关系,相关系数为0.999,方法检出限为2~5μg/L,相对标准偏差(RSD)为0.52%~2.51%(n=6),加标回收率为98%~101%,对标准物质进行测定,相对误差为0.5%~1.2%,结果较为满意。

Tribological properties improvement of conventionally-cast Al−8.5Fe−1.3V−1.7Si alloy by multi-pass friction stir processing

The effect of multi-pass friction stir processing(FSP)on the tribological properties of conventionally-cast Al−8.5Fe−1.3V−1.7Si(FVS0812)alloy was investigated.The pin-on-disk dry sliding wear tests were conducted at room temperature under the applied pressures of 0.25,0.50,and 0.75 MPa.The results showed that FSP substantially refined and improved the distribution of coarse¸-Al_(13)Fe4 platelets andα-Al_(12)(Fe,V)_(3)Si intermetallics in the microstructure of alloys and eliminated the intermetallic-related defects.Consequently,the mechanical properties of the alloys,especially their ductility,were improved,which enhanced the stability of the protective tribolayer formed on their worn surfaces.According to the wear test results,the FSPed samples showed improved tribological properties especially at the higher applied pressures.For instance,at the applied pressure of 0.75 MPa,the wear rate and average friction coefficient of four-pass FSPed sample were lower than those of the base as-cast sample by 97%and 52%,respectively.SEM examination of the worn surfaces and wear debris also demonstrated that the wear mechanism changed from severe delamination/abrasion and microcracking of the tribolayer in the as-cast samples to mild delamination/abrasion and minor plastic wear in the FSPed samples.

Microstructural characteristics of intermetallic phases in spray-deposition Al-8.5Fe-1.3V-1.7Si alloy

Analysis electron microtechnique (AEM) and high resolution electron microtechnique (HREM) studies were conducted on a spray deposition Al 8.5Fe 1.3V 1.7Si(mass fraction, %) alloy to determine the characteristics of the intermetallic phases. The results show that the striking characteristics of the microstructures in as deposited and as extruded alloys indicate the presence of a large amounts of homogeneously distributed fine particles and a few coarse particles, while small amount of eutectics consisted of α (Al) and α AlFeSi are found in local zone in as deposited alloy. The fine particle is identified to be bcc α AlFeSi phase, and the coarse particles are monoclinic α Al 13 Fe 4 equilibrium phase, bcc α AlFeSi phase and newly found hexagonal h AlFeSi metastable phase. In α Al 13 Fe 4 , stacking faults on (100) and (001) plane and microtwin on (100) twinning plane are frequently observed. The extra reflection spots in α AlFeSi reflection pattern can be induced by α AlFeSi superstructure. The hexagonal metastable phase transforms to bcc phase, and the compositions of two phases are very similar. A close crystallographic orientation relationship between hexagonal and bcc phases are determined, and HREM image shows that the interface between them is coherent. [

FORMATION OF QUASICRYSTALLINE PHASE IN RAPIDLY SOLIDIFIED Al-Fe-V-Si ALLOY

The icosahedral quasicrvstalline phase (i-phase) with the chemical composition of 82.4at%Al. 8.8at%Fe. 3.6at%V and 5.2at%Si in melt spun Al-Fe-V-Si ribbons was found. It is suggested that the temperature and holding time of the melt prior to quenching are the important factors in the formation of the i-phase.

Deformation Localization and Shear Fracture of a Rapidly Solidified Al-Fe-V-Si Alloy at Elevated Temperature

The tensile and fatigue behavior of a dispersoid strengthened, powder metallurgy Al-Fe-V-Si alloy at ambient and elevated temperatures was investigated. The results show that the strength and ductility of the alloy decrease significantly with increasing temperature and decreasing strain rate. Micro-structural examinations reveal that this change in mechanical behavior with increasing temperature is related to the mode of deformation of the alloy. Further observations show that localized shear deformation is responsible for the losses in both strength and ductility of the alloy at elevated temperature.

Changes of Tempering Microstructure and Properties of Fe-Cr-V-Ni-Mn-C Cast Alloys

The changes of tempering microstructure and properties of Fe-Cr-V-Ni-Mn-C cast alloys with martensite matrix and much retained austenite are studied. The results showed that when tempering at 200 °C the amount of retained austenite in the alloys is so much that is nearly to as-cast, and a lot of retained austenite decomposes when tempering at 350°C and the retained austenite decomposes almost until tempering at 560 °C. When tempering at 600 °C, the retained austenite in the alloys all decomposes. At 560°C the hardness is highest due to secondary hardening. The effect of nickel and manganese on the microstructure and properties of Fe-Cr-V-C cast alloy were also studied. The results show that the Fe-Cr-V-C cast alloy added nickel and manganese can obtain martensite matrix and much retained austenite microstructure, and nickel can also prevent pearlite transformation. With the increasing content of nickel and manganese, the hardness of as-cast alloy will decreases gradually, so one can improve the hardness of alloy by tempering process. When the content of nickel and manganese is 1.3-1.7%, the hardness of secondary hardening is the highest (HRC64). But when the content of nickel and manganese increase continually, the hardness of secondary hardening is low slightly, and the tempering temperature of secondary hardening rises.

MICROSTRUCTURES AND MECHANICAL PROPERTIES OF RAPIDLY SOLIDIFIED Al-Fe-Cr-Zr-V-Si ALLOY AND THEIR THERMAL STABILITY

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Relations among High-frequency Magnetic Properties and Frequency in Nanocrystalline Fe_(72.5)Cu_1Nb_2V_2Si_(13.5)B_9 Alloy

High-frequency magnetic properties, such as core loss, coercivity and amplitude permeabilityof a newly-developed nanocrystalline Fe72.5Cu1Nb2V2Si13.5B9 alloy in the wide ranges of f =20-103 kHz, Bm = 0.01~0.6 T and Bmf = 10~40 (T.kHz) have been measured. A largeamount of experimental data have been fitted by a computer, thus obtaining several expressionsrepresenting the influence of frequency on high-frequency magnetic properties, that are useful inpractical applications.

Influence of Neodymium on Amorphizability of RS Al-Fe-V-Si-Nd Alloys:An Investigation Using Time Dependent Nucleation Theory

Time dependent nucleation theory was applied to calculate the incubation time required for α Al nucleation in rapid solidified (RS) Al Fe V Si Nd alloys. The nucleation rates were calculated as a function of temperature, and the critical cooling rates required for the formation of amorphous α Al at different neodymium concentrations were calculated too. The addition of neodymium increases the amorphizablity of α Al by increasing the incubation time and decreasing the nucleation rate and the critical cooling rate. The calculations are fitted to experimental results when liquidus temperatures are estimated from an approximation, which treats Al Fe V Si Nd as quasi binary Al Fe system.

EXPERIMENT AND THERMODYNAMIC ANALYSIS ON THE PHASE STABILITY OF LOW ACTIVATION Fe-Cr-Mn(W,V) ALLOY

Phase stability of four different chemical component Fe-Cr-Mn(W, V) alloys are investigated by experimental method and thermodynamic model in this paper. It is indicated that the main phase of four alloys after aged under 623, 673, 773K for 200h are austenitic phase. The results of Thermo-Calc, which are based on Gibbs energy, show that the phases of four alloys under ihe same temperature as experimental method are single austenitic phase. The results of experimental method and Thermo-Calc agree well.

Effect of the Partial Substitution of V for Nb on the Magnetic Properties of Fe-based Nanocrystalline Alloy

The variation of the magnetic properties of the nanocrystalline alloys for the partial substitution of V for Nb with crystallizing treatment temperature and time was investigated. The variation law of the magnetic properties with the annealing temperature and time is essentially the same. The magnetic properties of the Fe-based nanocrystalline alloys for the partial substitution of V for Nb reduce, and the crystallizing treatment temperature of the alloys increases. The optimum properties of Fe74Cu1Nb3Si13B9 nanocrystalline alloys crystallized at 550℃x60 min are μ0=9.2xl0^4, μm=54.8xl0^4, Hc=1.14 A/m and Bs=1.26 T. The best properties for Fe74Cu1Nb3Si13B9 alloys annealed at 560℃x60 min are μ0=8.79x10^4, μm=50.18xl0^4, Hc=1.26 A/m and Bs=1.24 T.

Structure of melt-spun Al-2.5Ti-2.5Fe-2.5V alloy and structural changes during annealing

Rapidly solidified Al 2.5Ti 2.5Fe 2.5V alloy was prepared by melt spinning. As spun and as annealed microstructures were studied by TEM, HREM, XRD and EDS analysis. The microhardness of the alloy at different annealing temperature was measured. The results show that the as spun microstructure of the alloy includes four kinds of primary phases: Al 11 (V,Ti), AlTi 3, Al 80 (V,Ti) 20 and Al 82 (Fe,Ti,V) 18 phase. After annealing at 300 ℃ for 10 h, metastable phase Al 82 (Fe,Ti,V) 18 transforms to the stable phase Al 13 Fe 4. After annealing at 400 ℃ for 10 h, the primary phases Al 11 (V,Ti) and AlTi 3 has completely transformed to Al 80 (V,Ti) 20 and Al 23 Ti 9 phase, respectively. The addition of element V increases the microhardness of melt spun Al 2.5Ti 2.5Fe alloy at elevated temperatures.

Mossbauer Effect of Rapidly Quenched Al-Fe-V-Si-Mm Alloys

The iron atomic location in Al(93.3-x)Fe(4.3)V(0.7)Si(1.7)Mm(x)(x=0, 1, 3, 6) alloys was investigated by means of Mossbauer spectroscopy and X-ray diffraction. The results show that the appearance of bcc a-Al-13(Fe, V)(3)Si dispersive particles existing in Al-Fe-V-Si alloy is suppressed by:the addition of misch metal, A new Al-Fe-V-Si-Mm amorphous alloy is formed when the concentration of misch metal is up to 6 at%, in the meantime, the corresponding structural analysis is made using Voigt-based fitting method.

喷射成形Al-Fe-V-Si系耐热铝合金的数值模拟及组织分析

利用数值模拟方法模拟了在喷射成形Al Fe V Si系耐热铝合金过程中雾化液滴的飞行状态及凝固行为 ,给出了不同尺寸雾化液滴的冷却速度和固相分数随飞行距离的变化规律 ,并对雾化颗粒的形貌组织进行了观察分析。在雾化颗粒中观察到了尺寸在 1～ 10 μm的第二相 ,能谱及XRD分析表明这种第二相为Al12 (Fe ,V) 3

SiCp／Al-Fe-V-Si复合材料组织与性能的热稳定性

为研究SiCP/Al-Fe-V-Si复合材料的热稳定性,对多层喷射沉积技术制备的SiC颗粒增强Al-Fe-V-Si合金经过不同温度下的热稳定性实验后进行了硬度检测,并对其显微组织进行了电镜观察。结果表明:随着基体合金材料中Fe含量的提高,复合材料的组织和力学性能具有更好的高温稳定性。添加SiC颗粒后,SiC颗粒向基体中注入Si,由于基体中Si浓度的提高,减慢了合金中第二相弥散粒子的粗化和分解,与未添加SiC颗粒的合金材料相比,添加SiC颗粒复合材料的组织和力学性能具有更好的高温稳定性。

SiC颗粒增强Al-Fe-V-Si复合材料的SiC/Al界面形貌

采用喷射沉积工艺制备SiCp/Al-Fe-V-Si复合材料,并通过热压和热轧工艺对沉积坯进行致密化;通过高分辨电镜观察其SiC/Al界面形貌,并对比热暴露后的界面形貌。结果表明:复合材料主要存在两种SiC/Al界面,一种是厚度为3nm左右的晶态Si界面层,且在界面附近的基体中生成细小的Al4C3相;另一种是厚度为5nm的非晶态SiO2界面层,部分溶解的SiC颗粒向附近Al基体中注入游离态的Si,在界面附近形成Si的浓度梯度;两种界面都具有良好的润湿性,界面结合强度高;经640℃热暴露10h后,SiC/Al界面处生成的粗大Al4C3脆性相降低界面结合强度,从而降低复合材料的力学性能。

Fe-V合金碳化物析出型渗碳(CDC)组织

通过金相显微镜、扫描电子显微镜及X射线分析研究了Fe V合金CDC处理后表层的相组成、渗层组织和碳的扩散行为·结果表明所有Fe V合金渗层组织由表及里依次为γ +V4 C3 ,α +V4 C3 及α ,最表层碳化物的尺寸为 2 5 0nm ,随渗层的深入碳化物颗粒有所粗化 ,在α相区碳化物的尺寸达 2 5 μm ;CDC处理得到的奥氏体区的厚度与渗碳时间的平方根成正比 ,碳的扩散速度随合金质量分数的增加而降低·

添加Mg和Cu对Al-Fe-V-Si合金组织与性能的影响

采用OM、SEM、XRD、力学拉伸实验、硬度测试等手段研究了单独添加Mg及同时添加Mg和Cu对铸态Al-Fe-V-Si合金及其热挤压棒材显微组织和力学性能的影响。结果表明:添加Mg可以明显细化Al-Fe-V-Si合金的铸态组织,改善铝铁相的形貌与分布,还有利于提高合金的硬度与强度;同时添加Mg和Cu时,Cu部分抵消了Mg的细化作用,但经过热处理后,Mg2Si、Al2Cu和Al2CuMg相的形成,使合金的硬度与强度进一步提高。