Thermally induced martensite properties in Fe-29%Ni-2%Mn alloy

Thermally induced martensite properties in Fe-29%Ni-2%Mn alloy were investigated according to martensitic transformation kinetics, morphology, magnetism of both austenite and martensite phases and also in terms of martensitic transformation start temperatures (M_s) for different austenite grain sizes of alloy. Kinetics of the transformation was found to be athermal. Also only lenticular martensite morphology was observed during investigations. On the other hand, Mössbauer spectra revealed a paramagnetic character for austenite phases and a ferromagnetic character for thermally induced martensitic phases. Determined M_s temperatures were found to be at − 128 °C for large grained samples and − 135 °C for small grained samples.     

Damping performance and martensitic transformation of rapidly solidified Fe-17%Mn alloy

The rapid solidification of Fe-17%Mn alloy was performed to investigate the influence of cooling rate on its damping performance and martensitic transformation mechanism. A proper heat treatment was also carried out to clarify its coupled effects with rapid solidification. The stacking fault probability and martensitic transformation temperature were determined to demonstrate their relationship with the cooling rate and the heat treatment process. With the increase of cooling rate, the volume fr...     

Electrical resistance behaviour of Fe-24 wt.%Mn alloy under high pressure

Electrical resistance behaviour of Fe-24 wt.%Mn SMA was studied up to a pressure of ∼6 GPa by using an opposed anvil high pressure device. The system shows a steep rise in resistance up to ∼1 GPa and thereafter a monotonic decrease up to ∼6 GPa during the forward cycle, whereas it shows a monotonic increase during the return cycle. XRD studies of the as-prepared and pressure quenched samples show a mixed α, γ and ε phase in the former and a predominantly ε phase in the latter, indicative of a possible structural transition at ∼1 GPa, as evidenced from the resistance maximum. The decrease in the transition pressure, when compared with alloys of lower Mn concentration, provides a clue that it should be possible to further reduce the transition pressure to the predominantly ε phase by alloying with suitable elements, which may have positive effect on the shape memory of the alloy.     

Unusual stress-corrosion cracks observed in glassy Fe-40Ni-14P-6B alloy

The tendency of glassy Fe-40Ni-14P-6B to stress corrosion cracking (SCC and hydrogen embrittlement (HE) in aqueous acidic media was investigated. Cathodically polarized, elastically stressed specimens failed in 1 M MCl by HE, as did those immersed in aqueous polythionic acid at the free corrosion potential. Similar specimens immersed in aqueous FeCl₃ at the free corrosion potential failed by SCC, as did those anodically polarized in 1 M HCl. The FeCl₃ specimens were covered with an iron oxide film, and selective leaching of nickel from pits and cracks was observed. The remarkable cracking patterns observed in aqueous FeCl₃ reflect the isotropic, grain -free nature of the glassy alloy surface, and are thought to throw some light upon the internal stress profile of this interesting material.     

Tensile properties of a Fe-32Mn-6Si shape memory alloy

The tensile properties of a Fe-32Mn-6Si shape memory alloy were investigated. It was found that tensile properties depend on temperature, heat treatment and material structure. The relationships of martensitic transformation, tensile properties, and shape memory effect are discussed. Finally, we propose a macroscopic one-dimensional constitutive law describing the thermomechanical behavior in tensile loading. Numerically obtained results are close to the experimental ones. __________ Translated from Problemy Prochnosti, No. 2, pp. 55–65, March–April, 2008.     

Transport properties of antiferromagnetic superconductors

Transport properties of antiferromagnetic superconductors with T _N<T _chave been investigated. Detailed numerical results are given for SmRh₄B₄ by using the following model. The paramagnetic phase (T _NT _c)is described by using Abrikosov-Gorkov theory of magnetic ions in an ordinary superconductor. In the AF phase (TT _N)the effects of the molecular field H _Q (T) and the elastic scattering of conduction electrons from spin fluctuations are included. Expressions for H _Q (T) and the scattering rate from spin fluctuations have been derived. The aim has been to see if properties are enhanced or depressed by the AF ordering occurring below T _N.It is found that whereas the electronic thermal conductivity K _s,nuclear spin relaxation rate R _s,and the longitudinal ultrasonic attenuation _s,are depressed by the AF ordering, the inverse of the magnetic penetration depth, [(T)]^–1 is enhanced below T _N.The effect of all types of impurities is included in the study. Theoretical results for K _sand [(T)]^–1 agree with the experimental values for SmRh₄B₄ (experimental data for other properties are not available in literature). In the above, T _Nis the Néel temperature and T _cis superconducting transition temperature.     

颗粒形貌对Fe-35%Co合金吸收剂磁性能的影响

采用高能球磨的方法处理水雾化Fe-35%(质量分数)Co软磁合金粉末,运用SEM、VSM和矢量网络分析仪分析测试不同球磨时间下合金粉末的微观形貌和静磁参数及其1~18 GHz频率范围的复磁导率(μ=μ'-jμ″)。结果表明,球磨处理可以使合金粉末颗粒扁平化,使得其复磁导率实部和虚部均明显提高;随着球磨时间增加,合金粉末的饱和磁化强度逐渐减小、矫顽力逐渐增大、扁平率以及复磁导率实部和虚部均先增大后减小,过度球磨会使合金粉末软磁性能恶化,不利于其微波磁导率的提高。     

Fe-1.44%C-1.52%Cr-0.32%Si-0.62%Mn超高碳钢中温相变特征研究

为揭示超高碳钢中温相变特征,采用XRD物相分析、光学显微组织形态观察、硬度及冲击韧性测试等研究了Fe-1.44%C-1.52%Cr-0.32%Si-0.62%Mn超高碳钢在150、200℃等温条件下相变产物的组织结构及力学性能特点.实验结果表明:无论在150℃等温还是200℃等温,均发生贝氏体转变及碳化物的析出;贝氏体具有不同于直接淬火形成的针状马氏体的短棒状形貌,且在不同等温条件下形成的贝氏体组织具有不同的形貌特征;相比150℃等温,200℃等温时形成的贝氏体棒的长/宽比较大,且随着等温时间的延长,贝氏体棒呈现平行形成的状态,贝氏体组织的硬度水平随之降低.     

Fe-36Ni因瓦合金研究进展

概述Fe-36Ni单相奥氏体合金的强化机理和方法,介绍了这一领域近年来的研究进展,简述了Fe-36Ni因瓦合金焊接性能改善方面的研究成果.     

Magnetic properties and thermomagnetic analysis of a Fe-20Mo-5Ni-0.075C alloy

A Fe-20Mo-5Ni-0.075C (wt%) alloy for magnets was prepared by induction melting under vacuum. The material was hot rolled, solution treated and aged at 610°C for different periods of time. The magnetic properties (H_c, B_r, B_s and (BH)_max) were measured and compared with some commercial alloys containing cobalt. The precipitation of Mo-rich phases and the decrease of the ferrite lattice parameter during ageing were detected by X-ray diffraction. The thermomagnetic analysis (TMA) was carried out in the solution treated samples and aged samples. The behaviour of TMA curves was explained with the help of X-ray analysis.     

Effect of Cu content on microstructure and properties of Fe-16Cr-2.5Mo damping alloy

Five Fe-16 Cr-2.5 Mo damping alloys with different Cu contents(0%,0.25%,0.5%,1.0% and 2.0%) were prepared.The microstructure was observed by scanning transmission electron microscopy(STEM) and the damping behavior was measured by using a dynamic mechanical analyzer(DMA).The results show that the grain size of experimental alloy with(0.25–1.0%) Cu was refined compared with the 0 Cu alloy.The Cu element is fully dissolved in the matrix and there are no Cu precipitates and carbides observed.Although the internal stress increases because of Cu addition,the damping capacity of the 0.5 Cu and1.0 Cu alloys has been significantly improved.The reason of damping improvement is that the magnetic domain structure is strongly modified.Meanwhile,the strength was improved gradually due to the Cu solid solution strengthening and grain refining.In the 2.0 Cu alloy,lots of Cu-riched particles appeared in the matrix.These Cu precipitates with 10–15 nm in size are spherical and homogeneously distributed,which strongly induce strength improvement through precipitation strengthening.On the contrary,the elongation and impact energy of the 2.0 Cu alloy decrease sharply.In addition,lots of Cu precipitates will significantly decrease the damping capacity by hindering the mobility of domain walls.     

W、Mo添加对Fe-21Cr合金连接板高温性能的影响

Fe-Cr合金是固体氧化物燃料电池(SOF-Cs)连接板材料的最佳候选之一,但仍存在氧化速率较快以及热膨胀系数(TEC)较大等问题。采用热胀系数小的W和Mo元素,研究了W或Mo对Fe-21Cr合金热膨胀系数、面电阻及抗氧化特性的影响。研究结果表明,适量W或Mo的添加可以降低Fe-21Cr合金的热膨胀系数,并提高其750℃高温抗氧化性能。     

Ion-nitriding of an Fe-19 wt % Cr alloy

The ion-nitriding behaviour of an Fe-18.75wt% Cr alloy was investigated at 803 K under constant plasma conditions. Both a thin surface layer of-Fe₄N and an internal-nitriding layer were observed. The nitride formed in the internal-nitriding layer was found to be CrN, rather than Cr₂N. The hardness of the nitriding layer rises to Hv=1200 due to small CrN precipitates. The growth rate of the internal nitriding layer, in the present alloy is controlled by a nitrogen diffusion process in the matrix metal,-iron. Because such ion-nitriding behaviour is analogous to that of internal-oxidation, the growth rate of nitriding was discussed according to the rate equation to that of internal-oxidation. The nitrogen diffusion in the present alloy is scarcely affected by the CrN precipitates.     

Cu clusters evolvement in Fe-1.18%Cu binary alloy

Microstructure evolution of Fe-1.18%Cu binary alloy during solution and aging at 550°C was investigated under a high-resolution electron microscope (HREM). In addition, the aging strengthening mechanism was investigated based on the precipitation strengthening theory. Results show that there were lots of Cu atom clusters in the ferrite matrix during solid solution and initial aging stage, and Cu-rich metastable Fe-Cu particles precipitate subsequently at the aging hardness peak. It is found that there were high-density dislocations and stacking fault substructure in the Cu clusters that forms the obstacle of the dislocation motion, which should be the dominant reason of strengthening in the Fe-Cu alloy.     

Fe-40Ni合金的动态力学性能研究

利用金相观察、热模拟技术及扫描电子显微术(SEM)研究了Fe-40％ Ni合金在含Ti及无Ti条件下的高温应力-应变行为及变形后的应力弛豫行为,并观察了锻造样品中TiN颗粒的形态.实验结果显示:含Ni 40％的Fe-Ni合金在室温下保持了奥氏体组织,并有孪晶出现.在800～950℃范围内变形时只发生动态回复,1000℃以上变形时发生了动态再结晶.在Ti存在的情况下,变形温度达到1150℃时才发生动态再结晶.IF钢的模拟结果与不含Ti的Fe-40Ni合金呈现类似的趋势.由于TiN的应变诱导析出,明显延缓了变形后等温过程中的应力松弛速率.     

Fe-3%Si合金热变形过程中的组织演变

利用Gleeble-1500热模拟实验机对Fe-3%Si合金进行1173K、0.01s-1条件下的压缩变形,借助EBSD分析了不同应变量下晶界与热变形组织特征演变。发现晶体旋转动态再结晶机制与几何动态再结晶机制共同控制了动态再结晶过程:在小应变量阶段,晶体旋转的不均匀性使晶界附近区域优先形成完善亚晶,而晶粒内部呈现不完善的亚晶;随应变量增大,晶界附近区域取向差增加,小角晶界逐渐演变为大角晶界;在大应变量阶段,原始晶界附近区域形成的大角晶界相互接触,最终通过几何动态再结晶机制实现通体动态再结晶。