Fe—Mn—Ge合金γ→ε马氏体相变的研究

利用金相组织观察,透射电子显微镜（TEM）分析和点阵参数测定方法研究了Ge含量对Fe-24Mn合金马氏体相变和显微组织结构的影响。结果表明,Fe-24Mn合金在冷却过程中产生大量的ε马氏体,在较低Ge含量合金中的后形成马氏体可以穿越或终止在另一取向的先形成马氏体片中,宽大的马氏体片是由大量相互平行的层错构成,随Ge含量的增加,马氏体片之间以交截或平行为主,这一结果表明：Ge的加入使Fe-24Mn合金中奥氏体层错能增加,合金中的ε马氏体数量减少,马氏体转变开始点Ms降低,Ge增大Fe-24Mn合金奥氏体的点阵常数,但对Fe-24Mn合金形状记忆效应的影响并不显著。     

Fe—Mn基合金减振性能研究

本文研究了Fe-27Mn-3.5Si合金的ε马氏体和堆垛层错在其减振能力上所起的作用;同时通过热处理或冷轧的方法改变合金的显微组织,研究了Fe-Mn基合金中ε马氏体、霍朵层错及γ／ε相界等显微组织对减振性能的作用和影响。     

板条状马氏体的亚结构及形成机制

研究马氏体亚结构及形成机制具有重要理论意义和应用价值.应用35CrMo等材料,淬火为马氏体组织,采用JEM-2100电镜观察马氏体形貌和亚结构,发现35CrMo钢马氏体为板条状,亚结构除了高密度缠结位错外,还有高密度层错.结合2Cr13、Fe-15 Ni-0.6C合金试样的浮凸试验,应用隧道扫描显微镜观察表面马氏体浮雕形貌,测定浮凸的微细尺寸.综合上述试验结果,分析位错、层错形成机制.发现浮凸效应中没有出现位错滑移迹象,认为切变模型不能解释高密度位错和层错的形成.最后应用马氏体相变新机制分析了高密度缠结位错、精细层错的形成.     

Fe—Ni—Co—Ti合金马氏体的组织形态惯习面及晶界析出物对马氏体转变的影响

对经不同预处理的Fe－30.01Ni－8,97Co－2．96Ti铁基合金的马氏体的表面浮凸、组织形态、惯习面以及原奥氏体晶界析出物对马氏体转变的影响进行了分析研究。结果表明,经1200℃×30h奥氏体均匀化、700℃×9h时效的合金,其马氏体为透镜状,惯习面为｛225｝γ;经1200℃×30h奥氏体均匀化、室温时效1．7×104h的合金,其马氏体为透镜状＋薄片状,薄片状马氏体的惯习面为｛31015｝γ;原奥氏体晶界处的析出物抑制马氏体转变。     

马氏体相变研究的最新进展(四)

正3.2.4有色金属合金中的马氏体孪晶图47是Cu-11.42Al-0.35Be-0.18B合金的马氏体组织中的孪晶形貌,可见呈现竹节状,竹节长短不等。图48是Cu-11Al合金的马氏体组织的电镜照片,可见马氏体片中存在贯穿的层错,层错微细而分布较为均匀。由于这类马氏体的亚结构以微细层错为主,甚至为全层错亚结构,故可称为层错型马氏体。层错亚结构也不能用切变机制解释。     

Ti—8Al—1Mo—1V合金中的相变

应用透射电子显微术研究了不同热处理之后的Ti-8Al-1Mo-1V合金的显微结构。在合金的α相中出现有序反应,其临介温度是～525℃。电子衍射指出有序相为DO_(19)型超点阵。在870℃以上淬火β相发生马氏体转变,发现了二种类型的马氏体:低温形成的具有严重层错六角或面心立方的α′相和高温形成的六角结构的α″相。过饱和的β相、马氏体结构α′和α″相时效时形成α和β相的混合物,其反应机理决定初始结构。上述转变与某些机械性能有很大关系。文中说明了合金在双重退火和工业退火状态下的机械性能。     

形状记忆不锈钢

新近开发成功的ＦｅＭｎＳｉＣｒＮｉ形状记忆不锈钢具有良好的形状记忆效应 ,同时还具有很好的力学性能、机加工性、焊接性和耐蚀性 ,而且是这类功能材料之中最廉价的合金。形状记忆不锈钢具有低的堆垛层错能 ,其形状记忆效应涉及到应力诱发的面心立方奥氏体 (γ)向密排六方ε 马氏体的相转变及其在加热时的逆转变。其形状记忆效应的先决条件就在于能直接引起ε 马氏体形成的宽的堆垛层错。因此 ,可以通过以下措施来改善这种形状记忆不锈钢的形状记忆效应 ;降低堆垛层错能 ;提高奥氏体基体的屈服应力 ;减低马氏体相变的临界应力 ;避免不同…     

淬火温度对Fe-Mn-Si-Cr-Ni记忆合金形状记忆效应的影响

本文研究淬火温度对Fe-Mn-Si-Cr-Ni记忆合金形状记忆效应的影响，并从合金层错能和显徽组织两方面讨论了对其产生影响的原因。结果表明：合金的回复率随着淬火加热温度的升高而升高，700℃时达到最大值，随后又随温度的进一步升高而降低；淬火温度越高，热诱发ε马氏体数量越多，热诱发ε马氏体对形状记忆具有双重作用，适量的热诱发ε马氏体有利于提高形状回复率；随着淬火温度的升高，合金的层错几率有着和回复率相似的变化规律；层错几率越大，层错能越低，合金的回复率也就越高。     

钢轨踏面马氏体白层组织分析

用扫描电镜(SEM)对长期运行后的U71Mn钢轨踏面马氏体白层组织进行了分析。结果得出,曲线段钢轨踏面白层较直线段白层厚度深,硬度更高。随距表面距离增加,曲线段钢轨踏面白层内原奥氏体晶粒分别呈等轴状、长条状和非常细小的等轴状,原奥氏体晶粒内的马氏体形态随深度的增加,由以片状马氏体为主逐渐转变为以板条状为主的混合马氏体;而直线段钢轨踏面白层内原奥氏体晶粒均为长条状,且长轴方向平行于踏面,原奥氏体晶粒内为以板条状马氏体为主的混合马氏体。结合分析结果和可能的运行情况,作者认为,出现上述结果的主要原因是在钢轨使用过程中,由于蠕滑等原因造成表面温度急剧升高,超过了奥氏体的形成温度,使得组织中的碳化物发生不同程度的溶解,形成的奥氏体晶粒形状和大小,以及随后的快速冷却过程中得到的马氏体形态也与这种快速冷热循环有关。     

马氏体转变(十七)

正6有色金属中的马氏体相变通常,有色金属和代位型有色合金中发生的马氏体相变同样是具有表面浮突的无扩散位移型转变,但具有比较小的应变和小的热滞。马氏体的形态有片状和板条两种。马氏体的亚结构有堆垛层错、孪晶和位错。在相变中沿切变面发生孪生或滑移进行调整,以符合晶体结构的相变和形状上的改变,马氏体中亚结构的出现和相应数量取决于合金     

A QUENCHING INDUCED PLANAR DEFECT OF MARTENSITE IN Cu-Zn-Al ALLOY

A new kind of planar defect named non-basal plane stacking faults has been studied by usingtrace analysis and lattice image techniques.It has been found that they are located in(125)_M plane of martensite lattice.By lattice image observation,the non-basal plane stack-ing faults are argued to be induced by two incomplete basal plane stacking faults and may bethe results of rapid quenching.The defects are regarded as anomalous structures ofmartensite.     

N对TWIP钢马氏体相变及力学性能的影响

以传统TWIP钢为对比,测试了含N TWIP钢的力学性能,并利用XRD进行物相分析和TEM进行做观结构表征.结果表明,在由fcc或hcp结构向bcc结构马氏体进行相变时,晶体结构中的最大间隙由0.1047 nm降低至0.0725 nm.间隙原子N的存在显著增大bcc结构的晶格畸变能,提高α马氏体切变的阻力,因而强烈抑制α马氏体相变,导致组织中hcp结构ε相含量大幅度增加,提高了TWIP钢的强度,但也降低了钢的塑性.另外,奥氏体平均和区域层错几率的计算及微观组织分析结果表明,形变增加层错的数量,而马氏体相变消耗层错,从而减少层错数量.     

钢中马氏体的层错亚结构

研究发现淬火钢马氏体中存在层错亚结构具有重要理论意义。应用JEM-2100高分辩透射电镜观察35CrMo、2Cr13、W6Mo5Cr4V2等钢的马氏体时,发现存在层错亚结构。层错亚结构条纹微细,间距约为数纳米,且往往与位错伴生。层错的成因是在晶格重构过程中,因新旧相错配度等因素造成晶格错排时形成的。认为切变机制不能解释马氏体层错亚结构的成因。     

H_2S-H_2O系统中奥氏体不锈钢破裂机理的研究

用X-射线结构分析、扫描电镜和透射电镜等方法,研究了在H_2S—H_2O系统中使用的奥氏体不锈钢的破裂机理。结果指出,化学反应所产生的氢是造成破裂的主要原因。薄膜试样直接观察指出,在氢引起马氏体相变之前,氢使位错和层错大量形成。氢减弱铁的结合键是引起一系列变化的根本原因。     

FINE STRUCTURE VARIATION OF 18R MARTENSITE UNDER DEFORMATION IN POLYCRYSTALLINE CuZnAl AI JOY

The transmission electron microscopy has been used to investigate the fine structure variationof 18R martensite under deformation in a polycrvstalline CuZnAl shape memory alloys.Ithas been found that the strain is gabined by the reorientation of martensite variants in the ini-tial deformation stage.In addition to the result of optical microscopy studies,however,thereorientation is often incomplete and the interfaces among the prior variants still remain.A lotof twins will appear in martensite under enormous deformation,and the twin plane is(001)phane of martensite lattice.The dislocations has also been observed in some regions.In thiscase,the martensite will lose its thermoelasticitv and the shape memory effect will bedamaged.     

SUBSTRUCTURE AND CRYSTAL MORPHOLOGY OF MARTENSITE IN MEDIUM CARBON IRON ALLOYS

The morphologic,substructural and crystallographic characteristics of martensite in steels 60and 60Si2Mn have been investigated by means of optical and transmission electronmicroscopy combined with B-M phenomenological crystallographic theory.The average hab-it plane of martensite in medium carbon iron alloys is{225}_f.Experimental data on the habitplane and the orientation relationship between the austenite and martensite are in agreementwith the B-M theoretical calculation of using the Bain strain and lattice invariant shear on(100)[011]_f.     

MIDRIB AND LEDGE OF BAINITE IN A Cu-Zn-Al-Mn ALLOY

The bainitic transformation in a Cu-Zn-Al-Mn alloy has been examined with TEM.The re-sults show that the stacking faults and also the bainitic midrib are found at the beginning ofbainite formation in the alloy.The stacking fault planes can pass continuously through themidrib in bainite.The growth ledges occur at the broad faces and rims of bainite.The broadand narrow faces of th ledges are parallel to the fault plane and habit plane respectively.Boththeir Miller indices are {110}_(B2).The moving direction of ledges is parallel to the fault plane.It may be deduced that the bainite in alloy are initially formed by shear and the process ofgrowth are go verned by propagation o f fault planes.     

中碳铁合金马氏体的一些特征

应用光学显微术及透射电子显微术和B-M表象晶体学理论对60和60Si2Mn钢中马氏体的形态、亚结构与晶体学特征进行了研究。中碳铁基马氏体的平均惯习面为{225}_f。铁基马氏体的微观惯习面为{111}_f。实测惯习面、取向关系及切变方向等与利用Bain应变及(100)[011]_f点阵不变切变系按B-M理论计算的结果一致。     

REVERSIBLE TRANSFORMATION BETWEEN MATRIX AND MARTENSITE IN Ni-Ti SHAPE MEMORY ALLOYS

The reversible transformation between matrix and martensite in Ni-Ti shape memory alloyshas been dynamically observed under TEM.The orientation relation between martensite andaustenite as well as the structural change near the transition temperature has been also studiedwith the help of HREM SADP.The results show that the orientation relation betweenmartensite and austenite is[(?)11]_A//[(?)10]_M,[110]_A//[001]_M,(110)_A//(001)_M and theangle between((?)110)_A and(010)_M is about 6.5°.The crystal defects of martensite are foundto be twin and stacking fault,and the twin plane as(100).     

EFFECT OF MARTENSITE ORDERING ON SME IN A Cu-Zn-Al ALLOY

The correlation between the shape memory effect(SME)and the ordering degree inmartensite formed through various heat-treatment processes,e.g.ice water quenching,step-quenching and aging etc.,has been studied in a Cu-26Zn-4Al alloy.The martensite or-dering degree is estimated by △d,the spacing difference of some pairs of diffracting planeswith indices satisfying a relation of(h_1~2-h_2~2)/3=(k_2~2-k_1~2)/n(n=1 for 9R martensite,n=4for 18R martensite).M 18R martensite is obtained from step-quenching,in which the valueof △d increases with the holding duration of step-quenching,and the shape recoveryrate η increases synchronouslly.9R martensite is obtained from direct water-quenching,thevalue of △d is quite large and SME is also good at just quenching state.But both △dand η decrease continuously with aging time at room temperature.This stabilization phe-nomenon of martensite is explained by the observation of TEM lattice fringe image,and itmay be attributed to the clustering of quenched-in supersaturated vacancies at(001)_M close-packed plane in martensite and decreasing the ordering degree.A reduction in△d and η occuring in the specimens on step-quenching or aging at higher temperature,which may be related to the precipitation of the α-phase and the enrichment of solute atoms,decreases the ordering degree.