高牌号无取向电工钢热轧板常化退火组织的EBSD分析

借助于EBSD对比研究了常化退火对高牌号无取向电工钢热轧组织和织构演变的影响,分析了常化退火对热轧板各厚度层织构的演变规律。结果表明,常化退火改善了热轧组织的均匀性,并弱化了热轧变形的γ纤维织构。升高常化退火温度,可增大热轧板的晶粒尺寸,提高{100}和{110}织构组分占有率,有利于提高无取向电工钢成品板的磁性能。     

轧制工艺对低牌号无取向电工钢相变退火组织、织构与磁性能的影响

将低牌号无取向电工钢的原始铸坯采用不同的工艺轧制得到5组样品,在H_2气氛下进行相变退火处理,使其发生α→γ→α相变,采用EBSD、XRD和磁性能测量技术确定了不同轧制工艺对低牌号无取向电工钢相变退火组织、织构与磁性能的影响。结果表明,与常规再结晶退火处理相比,相变退火处理可显著粗化晶粒降低成品板铁损;相变过程中存在织构遗传现象,相比于热轧-冷轧工艺,直接冷轧工艺相变退火后更有利于获得{100}织构,并显著改善成品板的磁性能;低温热轧比高温热轧能保留更多的{100}取向晶粒,相变退火后成品板中的非{111}取向晶粒增多,并提高了成品板的磁性能;此外,工业板中P和Al元素的偏聚或氧化对相变退火后成品板的组织、织构与磁性能有不利影响。     

常化处理对薄规格取向硅钢织构的影响

利用EBSD和XRD技术对比分析了常化和不常化2种工艺对薄规格取向硅钢组织及织构的影响.结果表明,2种工艺条件下的初次再结晶和二次再结晶织构存在着明显的差异.经过常化处理的样品初次再结晶组织中{411}148和{111}112织构组分比不常化样品的低,但Goss织构组分比不常化样品的高;常化处理的样品二次再结晶织构多为锋锐的Goss织构,磁性能优异,而不常化处理的样品二次再结晶织构多为Brass织构和偏Goss织构.此外,经过常化处理样品的初次再结晶组织中Goss取向晶粒周围分布的20°~45°大角度晶界所占比例高于不常化处理样品.2种样品初次再结晶后的平均晶粒尺寸差别并不明显,均为20μm,而且整体晶粒尺寸分布也相近.常化处理对最终磁性能有决定性影响,主要体现在提高冷轧前Goss取向“种子”的比例以及优化再结晶组织中Goss取向晶粒周围的织构环境.     

无取向电工钢50W470的组织与织构演变

研究了无取向电工钢50W470在热轧、冷轧、退火过程中的组织和织构演变。结果表明,热轧板沿厚度方向组织、织构是不均匀的,表层至过渡层为再结晶组织,主要为黄铜与铜型织构;心部主要为α纤维织构。冷轧板主要为α纤维织构和γ纤维织构。成品板为再结晶组织,平均晶粒尺寸100 μm,主要为γ纤维织构。     

常化工艺对高牌号无取向硅钢组织和织构的影响

以Si质量分数为3.3%的高牌号无取向硅钢为研究对象,研究了常化处理对试验钢厚度方向组织和织构的影响。结果表明：高牌号无取向硅钢热轧板沿厚度方向组织及织构不均匀导致常化板沿厚度方向出现织构梯度;常化处理可以明显改善热轧板组织和织构,促进晶粒粗大均匀,降低α纤维织构强度,增强λ纤维织构强度,减弱γ纤维织构强度。950 ℃常化时,常化板沿厚度方向晶粒粗大均匀,λ纤维织构强度最大。     

高纯Cr17钢板厚方向织构演变、成形性能及表面皱折

以高纯Cr17铁素体不锈钢为实验材料,对比研究了热轧不退火、退火两种工艺对其板厚方向织构演变、成形性及表面皱折的影响。采用金相显微镜、X射线衍射技术及背散射电子衍射技术观察两种工艺条件下的组织和织构演变。结果表明:成品板各层织构特征存在显著差异,这是由于低温轧制过程中沿板厚方向不同应变状态导致的热轧织构梯度遗传所致。与热轧不退火相比,热轧退火有利于成品板各层γ纤维再结晶织构增强,偏离{111}<112>组分的程度减弱,α纤维织构弱化;有利于弱化成品板的带状晶粒簇,促使晶粒簇分布均匀分散。     

热轧组织对无取向硅钢织构的影响

采用X射线衍射仪分析无取向硅钢冷轧织构和再结晶退火织构的演化,研究了热轧组织对无取向硅钢织构以及磁性能的影响.结果表明,具有均匀、粗大晶粒组织的热轧板,冷轧形成更多的剪切带,导致成品板形成高的高斯织构组分,并提高了{100}织构强度,降低了γ纤维织构,最终导致成品磁感应强度升高,铁损下降.     

50W470无取向硅钢热轧板的组织与织构演变

研究了50W470牌号无取向硅钢在热轧、正火、冷轧和退火过程中组织和织构演变。结果表明,热轧板表面为发生再结晶的细小等轴铁素体,主要织构为{110}<115>,过渡层和中心处以α纤维织构和较弱的γ纤维织构主。正火板的平均晶粒尺寸为90.5 μm,正火减弱了热轧板中对磁性能不利的γ纤维织构。冷轧板织构为强的α纤维织构和较弱的γ纤维织构。退火板的平均晶粒尺寸为74.2 μm,退火板织构主要是以{111}<112>取向为主的γ纤维织构,{100}和{110}面织构分别达到了7%和5.9%。正火50W470无取向硅钢的平均铁损P1.5/50和磁感B50分别达到了2.99 W/kg和1.725 T。     

热轧组织对冷轧无取向硅钢退火织构及组织的影响

对不同加热温度处理的热轧低硅钢带进行了冷轧及退火实验,分析了热轧钢带的组织对冷轧无取向硅钢再结晶退火过程中的组织及织构的影响。结果表明:热轧组织对冷轧无取向电工钢冷轧板再结晶组织及织构演变有重要影响;等轴晶粒组织的热轧钢带比混晶组织的热轧钢带冷轧后再结晶退火快,且退火后晶粒尺寸均匀;随着等轴晶粒尺寸增加,冷轧退火后形成的冷轧硅钢{110}类型的织构增强,{100}类型的织构减弱;表明热轧组织为等轴晶粒时,不利于冷轧无取向硅钢磁性能的改善。     

热轧工艺对超纯Cr17铁素体不锈钢成形性能的影响

对一种铌、钛双稳定化的超纯Cr17铁素体不锈钢分别进行常规热轧和低温热轧,再依次进行相同的退火、冷轧及最终再结晶退火处理。对比研究两种热轧工艺对组织、织构演变及成形性能的影响规律。结果表明,与常规热轧相比,低温热轧能显著细化热轧组织、弱化α纤维织构并强化γ纤维织构,最终使冷轧退火板的γ纤维再结晶织构明显增强、偏离{111}<121>组分的程度显著降低,使珋r值增大、△r值减小。低温热轧是改善超纯Cr17铁素体不锈钢成形性能的有效途径。     

The oxidation properties of U-16.6 at.% Nb-5.6 at.% Zr and U-21 at.% Nb

The fundamental oxidation characteristics of two U-base alloys, U-16.6 at.% Nb-5.6 at.% Zr and U-21at.% Nb, in the temperature range 500–1000° C in oxygen at 0.05 Torr are described. Both alloys undergo large dimensional changes during oxidation at temperatures above 650° C due to stresses generated in the oxide during oxidation. Oxidation rate curves for both alloys were determined at 100° C intervals between 500 and 1000° C; the activation energy for the process is shown to be small. The morphology of the oxide scale formed on the two alloys is complex and is described in detail. Stresses estimated at 10⁶ psi are shown to develop in oxidizing specimens, and a mechanism for the generation of these stresses is proposed.Research sponsored by the U.S. Atomic Energy Commission under contract with the Union Carbide Corporation.     

A quantitative investigation of phase formation during annealing of cold-extruded elemental powder mixtures Ti-48 at. % Al and Ti-48 at. % Al-2 at. % Cr

Formation processes of titanium aluminides during annealing of cold-extruded elemental powder mixtures, Ti-48 at. % Al and Ti-48 at. % Al-2 at. % Cr, have been quantitatively investigated. The reaction between Ti and Al to form TiAl and Ti₃Al passes through several non-equilibrium states, during which Al₃Ti and Al₂Ti are formed. The volume fraction of Al₃Ti decreases exponentially with time, between 700 and 1000°C. The formation and dissolution of Al₂Ti can be approximated by a parabola of third order on the logarithmic time scale. During the formation of Al₂Ti the volume fraction of TiAl remains relatively constant. As dissolution of Al₂Ti begins, the volume fraction of TiAl increases up to the equilibrium value. The volume fraction of Ti₃Al continuously decreases from the initial concentration to the equilibrium value. With increasing temperature, the reaction processes are accelerated. Although the phase formation processes are not significantly altered by Cr additions, the reaction speed is reduced by about a factor of three. The effect of Cr on the reaction is discussed.     

The high-temperature oxidation of cobalt-21 wt.% chromium-3 vol.% Y2O3 alloys

Alloys of Co-21 wt. % Cr-3 vol. % Y ₂ O ₃ have been prepared by a mechanical alloying method, and oxidized in oxygen at 100 Torr in the temperature range 900–1200°C. The general effects of the dispersed oxide phase are similar to those reported for nickel-base alloys: the selective oxidation of chromium to form a continuous protective Cr ₂ O ₃ scale is promoted; the rate of growth of Cr ₂ O ₃ is reduced compared to dispersoid-free alloys; the adhesion of the Cr ₂ O ₃ is greatly improved; and the scale-forming reaction is probably at the scale-metal interface in the alloys containing the dispersoid, whereas it is at the scale-oxygen interface in dispersoid-free alloys. This last point has not been positively demonstrated. The improvement in adhesion is of particular significance, since the scales on cobalt-base alloys are prone to spallation, and it has been possible to study the mechanism of adhesion in more detail. It appears that in dispersoid-free material the metal recedes from the scale-metal interface, leaving the scale supported on the tops of metal peaks but this does not happen in the alloy containing the dispersoid, either because the growth direction of the scale has been changed, or because of changes in the substrate grain size. In general, the observations support the model proposed in an early study for the oxidation of Ni-20 wt.% Cr alloys containing oxide dispersions.This work has been supported by the Naval Air Systems Command under Contract No. N00019-71-C-0079.     

Influence of prior-austenite grain size on the oxidation behavior of 9 wt.% cr-1 wt.% Mo steel

The effect of grain size on the oxidation of 9 wt.% Cr-1 wt.% Mo steel (with prior-austenite grain sizes of 90, 210, and 360 m) has been studied at 973 K in air. After the initial stages of oxidation (up to 60 min), the fine-grain specimen (90 m) suffered heavy spallation. A similar spallation took place after 120 min in the case of the specimen with intermediate grain size (210 m), and after 360 min in a coarse-grain (360 m) specimen. This increase in the duration for the onset of pronounced spallation with grain size has been attributed to the smaller area of the grain boundaries which are the locations of higher growth stresses leading to spallation. This dependence of spallation characteristics on the alloy grain size has been confirmed by the incidence of higher acoustic-emission activity during AE monitoring. Scanning electron microscopy (SEM) has confirmed the occurrence of pronounced spallation of the oxides formed in the areas adjoining the grain boundaries.     

Microstructural analysis of thermally induced and deformation induced martensitic transformations in Fe–12.5 wt.% Mn–5.5 wt.% Si–9 wt.% Cr–3.5 wt.% Ni alloy

Martensitic transformations induced by thermally and compression deformation at room temperature in Fe–12.5 wt.% Mn–5.5 wt.% Si–9 wt.% Cr–3.5 wt.% Ni alloy were studied in detail by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). From microstructural observations, it was seen that heat treated samples exhibited regular overlapping of stacking faults and ɛ martensite plates were formed parallel to each other. Also, TEM investigations showed that the orientation relationship between γ (fcc) and ɛ (hcp) phases corresponds to Shoji–Nishiyama type. With applied low plastic deformation rate, only ɛ martensite occurred in austenite grain. As a consequence, 4 and 25% plastic deformation at room temperature caused ɛ martensite formation in austenite phase and the new ɛ (hcp) and α′ (bcc) martensite formation in martensite phases, respectively. Orientation relationship between ɛ and α′ phases was found by the electron diffraction analysis.     

Corrosion of continuous alumina-fibre reinforced Al-2 wt.% Cu-T6 metal-matrix composite in 3.15 wt.% NaCl solution

The corrosion performance of a continuous alumina-fibre reinforced metal-matrix composite (MMC) and its monolithic matrix alloy (Al-2%Cu-T6) was studied in 3.15 wt.% sodium chloride solution. Corrosion initiation sites, mapping of corrosion current density and pH at corrosion sites, mass loss resulting from immersion, and polarization behaviour were studied. Results show that the MMC exhibited inferior corrosion resistance as compared to its monolithic matrix alloy. Corrosion of the MMC initiated preferentially along the fibre/matrix interface or in regions of plastic deformation. The build-up of acidity at localized corrosion sites on the MMC was enhanced by the formation of micro-crevices caused by fibres left in relief as a result of corrosion.     

Oxidation of Fe-3 wt.% Cr alloy

The oxidation behavior and the oxide microstructure on Fe-3 wt. % Cr alloy were investigated at 800°C in dry air at atmospheric pressure. Two distinct oxidation rate laws were observed: initial parabolic oxidation was followed by nonparabolic growth. The change in the oxidation kinetics was caused by microchemical and microstructural developments in the oxide scale. Several layers developed in the oxide scale, consisting of an innermost layer of (Fe,Cr)₃O₄ spinel, an intermediate layer of (Fe,Cr)₂O₃ sesquioxide, and two outer layers of Fe₂O₃ hematite, each with different morphologies. Wustite (Fe_1–xO) and distorted cubic oxide (-(Fe,Cr)₂O₃) were observed during the iniital parabolic oxidation only.     

High-temperature sulfidation of Mo-50 Wt.% Re

Mo-50Re was sulfidized over the range of 1000–1100°C in sulfur vapor at pressures of 10^–4 and 10^–2 atm. The reaction kinetics followed the parabolic rate law with an activation energy of 55.4 kcal/mole for and 48.2 kcal/mole for atm. The pressure dependence varied between +1/4 to +1/6 for the slope of a plot of log K_p vs log .Analysis of the diffusional processes occurring in both the scale and the alloy substrate gave an expression for the ratio of the thickness of the scale and of the -phase as a function of the corresponding rate constants for the growth of each layer. Finally, the conditions required for the formation of the -phase layer between the outer scale and the alloy substrate were obtained in terms of the ratio between the diffusion coefficients of the two metals in the intermetallic compound.     

Mg-6.0%Zn-0.5%Zr-2.0%Nd-1.0%Y合金的时效强化研究

对挤压 轧制制备的Mg-6.0%Zn-0.5%Zr-2.0%Nd-1.0%Y合金进行T5、T6两种热处理,通过力学性能测试,试验合金的力学性能优于未添加稀土元素的ZK60合金,在T5处理时的硬度高于T6处理时的,由金相显微观察、透射电子图像分析可知,试验合金的强化来源于时效初期的过渡相与位错的交互作用,435℃×2h固溶 150℃时效后,Mg-6.0%Zn-0.5%Zr-2.0%Nd-1.0%Y合金的脱溶顺序为:GP区→过渡相)→平衡相).其时效温度-时效时间-脱溶产物之间的关系可用自由能-成分关系或过冷奥氏体等温转变曲线来表示.