FeMnSi基合金中层错几率的X衍射线形分析法测定

堆垛层错是一种对金属、合金的相变某些性质有重要影响的晶体缺陷。用Ｘ射线衍射线形分析法可以测定金属合金中的层错几率。本文采用近似函数和付立叶分析法测定了ＦｅＭｎＳｉ基形状记忆合金中的层错几率，得到了有规律地结果；同时，将两种方法所得的数据进行了比较，并讨论了近似函数的选择和工具线宽以错几率计算结果的影响。     

多晶Fe—28Mn—4Si合金组织和形状记忆效应

以光学显微镜和透射电镜观察了Ｆｅ－２８Ｍｎ－４Ｓｉ合金的组织结构，并以弯曲法测定合金的形状记忆效应（ＳＭＥ）的大小，分析了多晶Ｆｅ－２８Ｍｎ－４Ｓｉ合金的组织结构及其与ＳＭＥ的关系，合金在室温下存在大量的层错和ε马氏体，ε马氏体这间及其与层错间呈现严重的交叉，以弯曲法测定了合金在Ｍｓ点以下和以上的ＳＭＥ，Ｍｓ以上无预存ε马氏体状态时所测得的ＳＭＥ远大于Ｍｓ以下有预存ε马氏体状态的ＳＭＥ，表明预存ε     

Fe—Mn和Fe—Mn—Si粉末混合物的机械合金化

对Ｆｅ－２４Ｍｎ，Ｆｅ－２４Ｍｎ－６Ｓｉ成分的粉末混合物进行了机械球磨，并对不同时间的球磨样品进行了Ｘ射线衍射（ＸＲＤ）和Ｍｏ¨ｓｂａｕｅｒ谱测量。结果表明，球磨使得Ｆｅ、Ｍｎ、Ｓｉ在原子尺度上发生了混合，形成了顺磁性、面心立方结构的Ｆｅ－２４Ｍｎ或Ｆｅ－２４Ｍｎ－６Ｓｉ纳米晶合金，这是Ｆｅ、Ｍｎ或Ｓｉ原子由颗粒表面到体内扩散的结果。球磨６７ｈ以后结构未发生变化，表明形成的是一种热力学亚稳结构，这个结果与Ｆｅ－Ｍｎ和Ｆｅ－Ｍｎ－Ｓｉ合金在室温下的相图结构明显不同。     

FeMnSi形状记忆合金成形加工性分析

ＦｅＭｎＳｉ系形状记忆合金由于层错能低难以实现交滑移,因此,其成形加工性很差,成材率低,这是阻碍ＦｅＭｎＳｉ系形状记忆合金实现产业化的关键问题之一。本文通过测试Ｆｅ－１７Ｍｎ－５Ｓｉ－１０Ｃｒ－５Ｎｉ形状记忆全金不同温度、不同应变速率和变温下的应力应变曲线,分析了合金的成形加工性。结果表明,升高温度并控制应变速率可显著改善合金的成形加工性;在实际生产中,合金可在９５０￣７００℃之间进行变温成形加工     

Fe－Mn－Si－Ni－Co合金中形变应力诱发ε马氏体的稳定化及其对记忆效应的影响

Ｆｅ－２５．６Ｍｎ－５．１Ｓｉ－４．１Ｎｉ－１．８Ｃｏ（ｗｔ％）合金在一８０℃变形时，可逆应变量ε＿ｒ随预应变量ε＿ｔ增大而迅速增大；当ε＿ｔ＞２．５％，增大速度减慢；当４．２％＜ε＿ｔ＜１０．８％，ε＿ｒ基本保持恒定值。逆相变温度Ａ＿ｆ随ε＿ｔ增大而连续升高，但Ａ＿ｓ不随ε＿ｔ变化。应力诱发ε马氏体及其逆相变后的残留显微组织分析表明，应力诱发ε马氏体片在形成过程中因相互交叉产生塑性变形，引起稳定化，是引起多晶Ｆｅ－Ｍｎ－Ｓｉ系合金可逆应变量低的一个重要原因。文中还讨论了应力诱发ε马氏体稳定化的特点及可能的改善途径。     

Fe—17Mn—10Cr—5Si—4Ni合金低温应力诱发相变特点及其形状记？…

用Ｘ射线衍射分析、显微组织观察等研究了Ｆｅ－１７Ｍｎ－１０Ｃｒ－５Ｓｉ－４Ｎｉ合金在低温（低于室温）下应力诱发相变的特点及其形状记忆效应。合金在室温拉伸变形时,当应变量超过５％由于应力诱发ε马氏体的相变作用而形成的α′马氏体;当变形温度低于室温时应力优先诱发γ－α′马氏体转变。正是这种应力诱发相应特征的转变使合金的形状记忆效应在室温以下出现奇特低谷。     

Fe—Mn—Si形状记忆合金中元素对材料耐蚀性的影响

研究了Ｆｅ－Ｍｎ－Ｓｉ形状记忆合金中元素对材料耐腐蚀性能及形状记忆性能的影响。结果表明：在Ｆｅ－Ｍｎ－Ｓｉ合金中，随着Ｍｎ，Ｓｉ含量的增加，其耐腐蚀性能略有提高，但Ｍｎ含量过高会导致合金形状记忆性能下降。而在Ｆｅ－Ｍｎ－Ｓｉ合金中加入适量的Ｃｒ，可明显提高该合金的耐腐蚀性能，并使之具有良好的形状记忆性能。     

Fe－Mn－Si形状记忆合金中元素对材料耐蚀性的影响

研究了Ｆｅ－Ｍｎ－Ｓｉ形状记忆合金中元素对材料耐腐蚀性能及形状记忆性能的影响。结果表明：在Ｆｅ－Ｍｎ－Ｓｉ合金中，随着Ｍｎ、Ｓｉ含量的增加，其耐腐蚀性能略有提高，但Ｍｎ含量过高会导致合金形状记忆性能下降。而在Ｆｅ－Ｍｎ－Ｓｉ合金中加入适量的Ｃｒ，可明显提高该合金的耐腐蚀性能，并使之具有良好的形状记忆性能。     

铋基中间合金显微组织研究

介绍了Ｂｉ－Ｍｎ（及Ｂｉ－Ｍｎ－Ｆｅ）系和Ｂｉ－Ｎｉ（Ｂｉ－Ｎｉ－Ｆｅ）系高熔点铋中间合金的相及显微组织特征,以进一步建立含铋相的性质、数量与合金熔点间的定量关系。本文为Ｂｉ－Ｍｎ系、Ｂｉ－Ｎｉ系中间合金成份的优化提供了依据。     

明效Fe—Mn—Si—Co—Mo合金中应力诱发马氏体的逆相变与形状记忆效应

研究了时效对Ｆｅ－Ｍｎ－Ｓｉ－Ｃｏ－Ｍｏ合金的临界屈服应力,应力诱发马氏体逆转变以及形状记忆效应的影响,结果表明,随着时效温度的升高,室温下的母相屈服应力与应力诱发马氏体相变临界应力之差增大,应力诱发马氏体逆转变温度Ａｃ和Ａｆ升高,而形状忘儿应在６００℃时效时出现峰值。     

Martensitic Transformation in Fe-Mn-Si Based Shape Memory Alloys

1.IntroductionFe-Mn-Sibasedalloysbecomeonekindofim-portantshapememorymaterialssincethecompleteshapememoryeffect(SME)waJsfoundinFe-3OMn-1Sialloyresultedfromfcc(7)-+hcp(E)martensitictransformationin1982bySatoet.1.[i].WorksonfCc(7)-+hcp(E)havebeenextensivelypublishedinlasttenyears.Thepresentauthorhaspointedoutsomenewaspectsoffcc(7)-hcp(E)transformationinalloyswithlowstackingfau1tenergyandhasanalyzedtheSMEassociatedwithfcc(7)-hcp(E)transformationinFe-Mn-Sibasedalloys[2~4].Thispaperattempt…     

铁基形状记忆合金马氏体相变研究进展

铁基形状记忆合金的形状记忆效应和超弹性取决于合金的马氏体相变特征,掌握铁基合金的马氏体相变规律是开发和优化铁基形状记忆合金的前提。根据马氏体相变类型将目前发现的铁基形状记忆合金分成3类：Fe-Mn-Si系,Fe-Ni-Co系和Fe-Pt／Fe-Pd系,分别阐述了3类铁基形状记忆合金马氏体相变的研究进展,总结了铁基合金形状记忆效应的不同机理和影响马氏体相变特征的各种因素,探讨了开发新型铁基形状记忆合金的需要关注的方向。     

Training effect in Fe-Mn-Si shape-memory alloys

The training effect in Fe-Mn-Si shape-memory alloys has been examined by length change and electrical resistivity measurements. After 13 deformation-heating cycles, it was found that the major recovery took place at a temperature lower by 30 K than the first cycle. Simple thermal cycling also lowered the starting temperature of the reverse transformation and increased the finishing temperature. At the same time, the martensitic transformation temperature was found to increase significantly, for example by 35 K, at the 14th thermal cycle. The characteristics of shape-memory effect affected by development of the homogeneous and fine deformation structure by the thermal cycling are discussed in the light of the training effect.     

Néel transition and γ⇌ɛ transformation in polycrystalline Fe-Mn-Si shape memory alloys

Silicon lowers the Néel temperature,T _N, and enhances the paramagnetic characteristic of γ-Fe-Mn alloy, which results in a reduction of the stability of austenite and in the anomalous increase of electrical resistivity, ?, belowT _N becoming stronger, i.e. the anomalous ? belowT _N increases rapidly with increasing silicon content. The γ?? transformation occurs during cooling and heating, but γ→? martensitic transformation is suppressed below about 240 K, probably due to the ? phase transfer from paramagnetic to antiferromagnetic state. The ? (T) changes steeply, accompanying the Néel transition and the γ?ε transformation. Silicon increases the electrical resistivity and the magnetic susceptibility, χ, of γ-Fe-Mn alloy, and the ? phase obviously increases the electrical resistivity of Fe-Mn-Si alloys. The relation between the Néel transition, γ→? martensitic transformation and shape memory effect (SME), are discussed.     

预应变对铝基体中复合的TiNi合金丝马氏体逆相变的影响

采用示差扫描热分析(DSC)、X射线衍射(XRD)和扫描电子显微分析(SEM)等方法,研究了预应变对铝基体中复合的TiNi形状记忆合金丝的马氏体逆相变的影响.结果表明,预应变的TiNi丝发生两种逆相变,一种是热致马氏体(TIM)的逆相变,另一种是应力诱发马氏体(SIM)的逆相变.预应变样品的TIM逆相变的起始温度与未预应变样品的基本相同.SIM逆相变的起始温度随预应变的增大而升高.TIM和SIM逆相变的分数随预应变的增大而减少.     

Ni含量对激冷贫镍TiNi形状记忆合金薄带相变行为的影

用激冷甩带法制备了Til-xNix(x=45％～49.8％)(原子分数)形状记忆合金(SMA)薄带,用示差扫描量热仪研究了Ni含量对铸态及450℃、500℃退火态TiNi SMA薄带相变行为的影响.结果表明,冷却/加热时,铸态和退火态Ti1-xNix(x=45％～49％)SMA薄带发生A→M/M→A一阶马氏体相变;当Ni含量为49.8％时,铸态和退火态TiNi SMA薄带冷却时发生A→ R→M两阶段相变,加热时发生M→A一阶段相变.随Ni含量增加,TiNi SMA薄带马氏体正、逆相变温度范围先增大后减小,Ni含量为48％时相变温度范围最宽.退火态比铸态TiNi SMA薄带相变温度范围窄.随Ni含量增加,TiNi SMA薄带马氏体正、逆相变温度升高,相变热滞增大.当Ni含量为49％时,SMA薄带的马氏体相变温度达最大值,当Ni含量为49.8％时马氏体相变温度迅速下降.     

Perspective in Development of Shape Memory Materials Associated with Martensitic Transformation

By consideration of the characteristics of martensitic transformation and the derivation from the application of the group theory to martensitic transformation, it may be concluded that the shape memory effect (SME) can be attained in materials through a martensitic transformation and its reverse transformation. only when there forms single or nearly single variant of martensite, with an absence of the factors causing the generation of the resistance against SME. on this principle, various shape memory materials including nonferrous alloys. iron-based alloys and ceramics containjng zirconia are expected to be further developed. A criterion for thermoelastic martensitic transformation is presented, Factors which may act as the resistance against SME in various materials are briefly described     

稀土元素对富Ni的Ti-Ni形状记忆合金马氏体相变的影响

在本文中,向Ti-50.7at.%Ni合金分别加入1at.%的稀土元素Ce、Dy、Gd和Y,并利用X射线和示差扫描热分析研究了稀土掺杂对富Ni的Ti-Ni合金马氏体相变行为的影响.结果表明:向富Ni的Ti-Ni合金中添加稀土元素能使合金的马氏体相变温度显著增加,且添加稀土Ce使合金相变温度的增幅最大.此外,Ti-50.2Ni-1Gd和Ti-50.2Ni-1Y合金中发生两步马氏体相变,而添加Ce和Dy的Ti-Ni合金中仍只发生一步马氏体相变.     

Hydrostatic pressure effect on the structural phase transitions in Ni-Mn-Ga alloy

In this paper dependences of characteristic temperatures on hydrostatic pressure for intermartensitic and martensitic transformations in Ni-Mn-Ga alloy are presented. In particular, intermartensitic transformation from martensitic phase with seven-layers periodicity to nonmodulated martensitic phase was studied by measurements of electrical resistivity under pressure. On the basis of these data an estimate of the transformation volume effect was made. It was found that transformation volume effect of intermartensitic transformation is an order of magnitude lower than that of martensitic transformation in this alloy.     

Time–dependent nature and origin of displacive transformation

We have investigated athermal and isothermal martensitic transformations (typical displacive transformations) in Fe–Ni and Fe–Ni–Cr alloys under pulsed and static magnetic fields and hydrostatic pressures in order to understand the time-dependent nature of martensitic transformation, that is, the kinetics of martensitic transformation. Also, we have calculated electronic structures of B₂ and ζ′₂ phases in AuCd by FLAPW and/or LAPW methods in order to understand the origin of B₂–ζ′₂ transformation. The following results were obtained. (i) The two transformation processes are closely related to each other, that is, the athermal process changes to the isothermal process under a hydrostatic pressure and the isothermal process changes to the athermal one under a magnetic field. (ii) These findings of (i) can be explained by the phenomenological theory, which gives a unified explanation for the two transformation processes previously proposed by our group. (iii) The calculation of the generalized susceptibility, x(q), for the B2 phase of AuCd shows that there exists a nesting vector of near 1/3<110>2Π/a as in the B2 phase of TiNi calculated previously. The density of states at the Fermi energy of the ζ′₂ phase is lower than that of the B2 phase, which is similar to the case of B2–R transformation in TiNi previously calculated.