渗铝低碳带钢的合金化反应

由于在表面形成稳定的氧化膜而使铝化钢有极好的抗氧化性,因此,常用于在高温环境下的部件,当铝化钢加热到873K以上时,涂层和钢基之间产生扩散,结果涂层变为由几种金属间化合物组成的混合层。在本研究中,铝化钢在873K温度下保温不同时间,用SEM—EDS分析了每一试样表面形成层的成分,每一层分析的成分与由热力学计算的Al—Fe—Si相图进行比较,以确定每一层的不同,在873K温度下检测了铝化层与钢基之间的扩散途径,观察到金属间化合物层的中间层中的Al含量比其它层中的低,由铝化层的成分判断,是由相互作用的两相细晶混合物组成。TEM—EDS分析表明铝化层是由Fe2Al5和T1两相混合组成。     

铝对310S耐热钢高温抗氧化性能的影响研究

采用增重法研究了通过WS-4非自耗真空电弧炉制备的w(Al)为2%～10%的310S耐热钢在1 200℃×30h空气中的抗氧化性能.用扫描电镜(SEM)观察了氧化层的表面形貌,X射线衍射仪(XRD)分析了氧化膜层的相组成.研究表明:加人铝后显著提高了310S钢的高温抗氧化性能,且310S钢的高温抗氧化性能随着铝含量的增...     

稀土元素提高Fe—Cr—Al系耐热合金抗氧化性的研究概况

Al_2O_3氧化膜是耐热合金保护膜中性能最好的氧化膜之一,但其显著的剥落性降低该类合金抗氧化性。向Fe—Cr—Al合金中加入稀土或活性元素,可以显著增加Al_2O_3保护膜与基体间的结合力,使该类合金抗氧化性得以提高。现已提出很多机理来解释稀土的作用,本文对这些机理进行了综述。     

8407钢渗铝氧化处理形成的氧化膜组织与结构

对渗铝后的8407钢试样进行常温硬质阳极氧化处理,使其表面形成氧化膜。通过金相显微镜观察氧化膜横截面组织,并探讨了氧化膜的形成机制;采用扫描电镜观察氧化膜表面形貌,并检测氧化膜沿厚度方向的化学成分及其分布;利用X射线衍射仪对氧化膜相组成进行分析。结果表明,渗铝8407钢经过常温硬质阳极氧化后,试样表面分为3层,从基体向外侧依次为基体、渗层、氧化膜。氧化膜连续致密,厚度均匀,与基体结合紧密,其主要成分为O、Al和Fe,且各元素分布均匀,主要相组成为Fe3O4和Al2O3。     

铁 铬 铝合金中铬的第三组元作用

 研究了Fe 10Al、Fe 5Cr 10Al和Fe 10Cr 10Al合金在1 000 ℃的氧化行为，利用电子显微镜和俄歇电子谱分析了合金表面氧化膜的形貌及组成。讨论了三元Fe Cr Al合金形成保护性氧化膜的机理，对于不发生铝的内氧化情况提出了合金中第三组元铬的作用机制：在氧化初始阶段，铬与合金中其它两组元——铁和铝一起氧化形成各自的氧化物，铬在氧化膜内最大含量的位置处于铁和铝的最大含量位置之间；铬降低了氧化膜内的铁含量，提高了初期氧化膜的保护性，从而促进选择性氧化铝膜的形成。     

Nb元素对粉末冶金TiAl基合金高温氧化行为的影响

采用等离子旋转电极法制备Ti-47Al-2Cr-0.2Mo,Ti-50Al-2Nb-0.3W和Ti-45Al-7Nb-0.3W(元素含量均为原子分数,%)3种预合金粉末,再通过热等静压制备成块体合金,在950℃空气环境中进行合金的高温氧化实验,并利用扫描电镜(SEM)观察与分析合金氧化后的表面形貌以及截面的元素面分布,用X射线衍射(XRD)分析氧化膜的相组成,研究Nb元素及其含量对Ti Al基合金高温氧化行为的影响。结果表明:Nb元素的添加可提高粉末冶金Ti Al基合金的抗氧化性能,这3种合金中Ti-45Al-7Nb-0.3W合金的抗氧化性能最好,经过80 h氧化后质量增量仅为2.484 mg/cm2,为不含Nb合金的12.44%,并且氧化膜整体厚度最薄,最厚的地方氧化膜厚度约为8.3μm。该合金表面形成连续致密的Al2O3氧化层,氧化膜从外向内依次为TiO2层/Al2O3层/(Ti,Nb)O2层/富Al和Nb层。     

铝合金压铸用模具钢表面的渗铝氧化处理

对8407模具钢试样进行热浸渗铝,在试样表面形成了Fe-Al合金渗层.对渗铝试样进行高温氧化实验,使渗层表面形成了Fe-Al-O的混合氧化物.考察了渗铝温度和渗铝时间对渗层质量的影响;着重研究了不同氧化气氛下Fe-Al合金表面的氧化情况,确定了最佳高温氧化工艺.结果表明,8407钢热浸镀铝后,在600 ℃以下、纯O2气氛条件下氧化,Fe-Al合金表面生成了Fe3O4和Al2O的混合物.这层氧化膜与铝液不润湿,能较好地保护试样.因此这种工艺可能是合适的铝合金压铸模表面处理工艺.     

45钢热浸镀铝扩散退火后的结构与性能研究

采用X射线衍射仪(XRD)和能谱仪(EDAX)对45钢热浸镀铝扩散退火后表层和渗层的组织结构进行了研究,结果表明,表层为Al2O3,过渡层为FeAl、Fe3Al化合物.采用失重法研究了45钢热浸镀铝扩散退火后的抗高温氧化性能和耐磨性研究,高温氧化试验结果表明,渗铝45钢的抗氧化性能和与1Cr18Ni9Ti不锈钢的抗氧化性相当,耐磨性优于调质处理的45钢.     

铝对HP40合金高温抗氧化性能的影响

 采用增重法研究了w(Al)=5%~10%的HP40合金在1 200 ℃×30 h空气中的抗氧化性能。结果表明,铝可显著提高合金的高温抗氧化性能,而且合金的高温抗氧化性能随铝含量增加而提高。1 200 ℃时,合金氧化增重与氧化时间的关系呈抛物线规律,氧化速率随氧化时间延长而逐渐下降。加入铝,改变了合金氧化膜层的物相组成和致密度,含铝合金的氧化层中含有Al2O3,而且Al2O3量随铝加入量增加而增多。     

微合金元素B对轻质TWIP钢组织及力学性能的影响

摘要：将质量分数为0.002%的微合金元素B加入至Fe-28Mn-9Al轻质TWIP钢中，以期改善其强塑积及室温冲击性能。利用X射线衍射、扫描电镜、电子万能拉伸试验机和金属摆锤冲击试验机对热轧TWIP钢的物相组成、微观组织、力学拉伸性能及室温冲击韧性进行了研究与分析。结果表明，微合金元素B的添加具有延缓奥氏体向铁素体转变的作用，细化了奥氏体晶粒，提升了钢的力学性能，TWIP钢的塑性、强塑积和冲击韧性均有明显的提高。     

Tensile Deformation Behavior of Fe-Mn-Al-C Low Density Steels

Room temperature tensile tests of Fe-Mn-Al-C low density steels with four different chemical compositions were conducted to clarify the dominant deformation mechanisms.Parameters like product of strength and elongation,as well as specific strength and curves of stress-strain relations were calculated.The microstructures and tensile fracture morphologies were observed by optical microscope,scanning electron microscope and transmission electron microscope.The tensile behavior of low density steel was correlated to the microstructural evolution during plastic deformation,and the effects of elements,cooling process and heat treatment temperature on the mechanical properties of the steels were analyzed.The results show that the tensile strength of steels with different cooling modes is more than 1 000 MPa.The highest tensile strength of 28Mn-12Al alloy reached 1 230 MPa,with corresponding specific strength of 189.16 MPa·cm~3·g~(-1),while the specific strength of 28Mn-10 Al alloy was 178.98 MPa·cm~3·g~(-1),and the excellent product of strength and elongation of 28Mn-8Al alloy was over 69.2 GPa·%.A large number of ferrite reduced the ductility and strain hardening rate of the alloy,while the existence of κ carbides may improve the strength but weaken the plasticity.Some fine κ carbides appeared in the water-quenched specimen,while coarse κ carbides were observed in the air-cooled specimen.High temperature heat treatment improved the decomposition kinetics of γ phase and the diffusion rate of carbon,thus speeded up the precipitation of fine κ carbides.The dominant deformation mechanism of low density steel was planar glide,including shear-band-induced plasticity and microbandinduced plasticity.     

铝对铁素体耐热不锈钢高温氧化行为的影响

 为了探究不同铝含量对X10CrAlSi18铁素体耐热不锈钢高温氧化行为的影响,采用恒温氧化方法对0.63%Al 和1.06%Al(质量分数)两组钢在700 ℃空气下进行高温氧化研究,测定和计算了氧化增重和平均氧化速率,观察分析了氧化形貌与氧化物相组成。结果表明,两组钢均达到了完全抗氧化级别,但1.06%Al钢的氧化增重和氧化速率均小于0.63%Al钢,表现出较好的抗高温氧化性;两组钢氧化膜均由3层组成,内层为Al₂O₃和SiO₂,中间层为Cr₂O₃和Fe₂O₃,外层则为MnCr₂O₄和FeMn₂O₄;随着铝含量的增加,氧化膜较为连续、致密,且与基体之间附着性较好,同时内氧化明显减少。     

Intermetallic diffusion coatings for enhanced hot-salt oxidation resistance of nitrogen-containing austenitic stainless steels

This article presents the preparation, characterization, and hot-salt oxidation behavior of nitrogen-containing type 316L stainless steel (SS), surface modified with intermetallic coatings. Three different types of intermetallic coating systems, containing aluminum, titanium, and titanium/aluminum multilayers, were formed by diffusion annealing of type 316L austenitic SS containing 0.015, 0.1, 0.2, and 0.56 pct nitrogen. Analysis by using X-ray diffraction (XRD), scanning electron microscopy (SEM), and secondary ion mass spectroscopy (SIMS) confirmed the formation of various intermetallic phases such as AIN, Al₁₃Fe₄, FeAl₂, FeTi, Ti₂N, and Ti₃Al in the coatings. Hot salt oxidation behavior of the uncoated and surface-modified stainless steels was assessed by periodic monitoring of the weight changes of NaCl salt-applied alloys kept in an air furnace at 1023 K up to 250 hours. The oxide scales formed were examined by XRD and stereomicroscopy. Among the various surface modifications investigated in the present study, the results indicate that the titanium-modified alloys show the best hot-salt oxidation resistance with the formation of an adherent, protective, thin, and continuous oxide layer. Among the four N-containing alloys investigated, the titanium and Ti/Al multilayer modified 0.56 pct N alloy showed the best hot-salt oxidation resistance as compared to uncoated alloys. The slower corrosion kinetics and adherent scale morphology indicate that the surface-modified titanium intermetallic coatings could provide high-temperature service applications up to 1073 K, particularly in chloride containing atmospheres, for austenitic stainless steels.     

Glass Forming Ability and Magnetic Property of Fe74Al4Sn2 （PSiB）20 Amorphous Alloy

Amorphous ribbons of Fe74 Al4Sn2 (PSiB)20 alloy have been synthesized by melt spinning and axial design method. The thermal properties of the amorphous ribbons have been measured by differential scanning calorimeter (DSC). The DSC results show that the Fe74 Al4Sn2P12Si4B4 amorphous alloy has relatively wider supercooled liquid region with a temperature interval of 40.38 K (△TX=TX-TR). The alloys with a higher phosphorous content in the metalloid element composition triangle of Fe74Al4Sn2(PSiB)20 have high glass forming ability. The amorphous alloys also show good magnetic properties in which Fe74Al4Sn2P6.67Si6.67B6.67 alloy has a large maximum permeability (μm), Fe78AlSn2P3Si3B10 alloy exhibits a high squareratio (Br/Blo) and FeT~A14Sn2P, Sil2B4 shows a low core loss (P0.5 1.3T). High glass forming ability and good magnetic properties make Fe74Al4Sn2(PSiB)20 amorphous alloys valuable in future research.     

Electron microscopy study of the passivating layer on iron-nickel martensite

A passivating oxide layer is known to form rapidly on the surface of Fe or Fe alloys exposed to air at low temperature. The properties of this passivating layer largely control the low temperature oxidation and corrosion properties of iron. It is hence important that the nature of this passivating layer be well understood. The work reported here principally involved a transmission electron microscopy examination of the thin oxide film formed on the surface of Fe?12Ni alloys on exposure to air at room temperature. Using high resolution microscopy the oxide particles of the film could be directly resolved and their structure and morphology characterized. The following conclusions were drawn from these characterization studies: 1) a passivating oxide layer (principally Fe₃O₄) forms spontaneously on the surface of Fe?Ni alloys on exposure to air at room temperature; 2) the orientation relation between the oxide and the metal surface depends on surface orientation; the Bain relation is obeyed when the alloy surface is (100)_α while the Nishiyama-Wasserman relation is obeyed on other low index surfaces. This phenomenon is attributable to the need to accommodate the misfit strain between the oxide and the substrate; 3) the oxide layer consists of dispersed, small (～20Å) oriented particles rather than a continuous thin film; and 4) the size of the oxide particles and the density of their distribution is related to the crystal surface orientation and condition.     

Internal oxidation of NiAl and NiAlSi alloys at the dissociation pressure of NiO

NiAl and NiAlSi alloys were internally oxidized at temperatures of 1073–1273 K by the Rhines Pack method. For the NiAl alloy, the oxidation process follows parabolic law and the oxidation front was flat with severe integranular oxidation occurring at 1073 K and extensive grain boundary sliding at 1273 K. As for NiAlSi alloys, the oxidation rate increased with increase of Si content at 1073 K but the rate decreased at higher temperatures due to total or partial continuous oxide layer formation at the internal oxidation front. The depth of intergranular oxidation was also greatly reduced. For all samples, nickel was found to be transported out to the surface with the amount proportional to the Si content. Lattice diffusion (Nabarro-Herring creep) was believed to be the main cause for nickel transport in the NiAl alloy while dislocation pipe diffusion is the mechanism for NiAlSi alloys.     

Effects of AlMnCa and AlMnFe Alloys on Deoxidization of Low Carbon and Low Silicon Aluminum Killed Steels

 To confirm the effects of AlMnCa and AlMnFe alloys on the deoxidization and modification of Al2O3 inclusions, experiments of 4 heat low carbon and low silicon aluminum killed steels deoxidized by AlMnCa and AlMnFe alloys were done in a MoSi2 furnace at 1 873 K. It is found that the 1# AlMnCa alloy has the best ability of deoxidization and modification of Al2O3 inclusions than 2# AlMnCa and AlMnFe alloys. Steel A deoxidized by 1# AlMnCa alloy has the lowest total oxygen content in the terminal steel, which is 37×10-6. Most of the inclusions in the steel deoxidized by 1# AlMnCa alloy are spherical CaO containing compound inclusions, and 891% of them are smaller than 10 μm. The diameter of the inclusion bigger than 50 μm is not found in the final steels deoxidized by AlMnCa alloys. Whereas, for the steels deoxidized by AlMnFe alloys, most inclusions in the terminal steel are Al2O3 or Al2O3 MnO inclusions, and a few of them are spherical, and only 768% of them are smaller than 10 μm. Some inclusions bigger than 50 μm are found in the steel D deoxidized by AlMnFe alloy.     

Multiscale Characterization of the Work Hardening Mechanisms in Fe–Mn Based TWIP Steels

When strained in tension, high‐manganese austenitic twinning induced plasticity (TWIP) steels achieve very high strength and elongation before necking. The main hypotheses available in the literature about the origin of their excellent work hardening include deformation twinning and dynamic strain ageing. In order to provide some answers, various experiments at different scales were conducted on Fe–Mn–C steels and the Fe–28 wt%Mn–3.5 wt%Al–2.8 wt%Si alloy. At a macroscopic scale, tensile tests were performed on all the studied grades. It was shown that, though the Fe–Mn–Al–Si based alloy retains very high elongation, the Fe–Mn–C steels properties are even more extraordinary. Tensile tests at different strain rates with the help of digital image correlation were also performed on the Fe–20 wt%Mn–1.2 wt%C steel to study the PLC effect occurring in this type of steel. It is suggested that supplementary hardening could come from reorientation of Mn–C pairs in the cores of the dislocations. At a microscopic scale, the Fe–20 wt%Mn–1.2 wt%C TWIP steel and the Fe–Mn–Al–Si grade were thoroughly investigated by means of in situ TEM analysis. In the Fe–Mn–C steel, the formed twins could also lead to a composite effect, since they contain plenty of sessile dislocations. In the Fe–Mn–Al–Si alloy, mechanical twins are thicker and contain fewer defects, leading to a lower work hardening than the other grade.     

微量稀土元素Tb、La掺杂对Fe-Al合金结构和磁致伸缩性能的影响

为了研究微量稀土元素Tb和La掺杂对Fe81Al19合金结构和磁致伸缩性能的影响及影响机制,采用真空电弧熔炼法制备了Fe81Al19、Fe81Al19La0.1和Fe81Al19Tb0.1三种铸态合金。用X射线衍射仪(XRD)和扫描电镜联合能谱仪(SEM/EDS)分析了合金的微结构。用振动样品磁强计(VSM)和磁致伸缩测量仪测试了合金的磁性能和磁致伸缩系数。结果表明,Fe81Al19合金由单一的bcc结构A2相组成,而掺杂稀土后的Fe81Al19Tb0.1和Fe81Al19La0.1合金均由bcc结构的A2主相和少量富稀土相组成。稀土Tb和La的掺杂使Fe81Al19合金沿<100>晶向择优取向,且Fe81Al19Tb0.1合金择优取向更加明显。此外,三种合金的磁化功大小排序为:Fe81Al19Tb0.1> Fe81Al19La0.1> Fe81Al19。表明稀土元素掺杂导致Fe-Al合金具有更大的磁晶各向异性,且Tb的掺杂效果更加明显。磁致伸缩系数测试表明,与Fe81Al19合金相比,稀土掺杂合金的磁致伸缩系数明显增大,而且Fe81Al19Tb0.1合金的磁致伸缩系数增大的更加明显,大约是Fe81Al19合金的3.2倍,为86×10^-6。稀土掺杂合金磁致伸缩系数增大的原因主要源于掺杂稀土使Fe-Al合金沿<100>晶向择优取向和稀土导致合金具有高磁晶各向异性。