Cu—Zn—Al合金中温相变产物的组织和结构

测定了Cu-27.27 Zn-3.73 Al Wt-%合金直接从高温母相淬火至中温的等温转变曲线.用金相、X-射线和电镜对直接淬火和从DO_3有序母相上淬至中温的转变产物做了形貌与结构的观察和分析.实验表明,依照转变产物,可将两个分离相接的c曲线分为三个区间:棒状α相,α相与片状贝氏体的混合组织,片状贝氏体.上淬所形成的贝氏体与直接淬火的贝氏体形貌相同.随时效时间的延长,贝氏体逐渐变成α相,它与从母相平衡析出的α相的点阵常数没有差别,由B2和DO_3母相所形成的贝氏体为接近正交的长周期结构,而且DO_3母相所形成的马氏体为单斜结构,它们分别对应(1210)与(2010)衍射峰的重叠和分离,表示前者的有序度较低.     

贝氏体碳化物的形成机理—贝氏体相变新机制

研究贝氏体碳化物的形成规律具有重要理论意义。实验观察表明,在有碳化物贝氏体中只有θ-渗碳体和ε-Fe_(2.4)C,没有特殊合金碳化物。贝氏体碳化物呈短棒状,沿着BF的长轴方向分布(上贝氏体)或与贝氏体铁素体片呈角度分布(下贝氏体),分布于贝氏体铁素体片条内部,即贝氏体碳化物(BC)被贝氏体铁素体包围。贝氏体碳化物来源于贝氏体铁素体片条之间的富碳奥氏体或贝氏体亚单元间的富碳奥氏体。碳化物在BF/γ相界面上形核,并且向奥氏体内部长大。贝氏体碳化物的形核-长大是依靠界面原子非协同热激活迁移实现位移,铁原子和替换原子在BC/BF相界面和Bc/γ相界面上热激活跃迁,BC向奥氏体内长大,也可以向铁素体内长大。     

扫描隧道显微镜研究Cu－Zn－Al合金中贝氏体及其浮突

用扫描隧道显微镜（ＳＴＭ）在大气中研究了Ｃｕ－２７．２Ｚｎ－４．７Ａｌ合金中贝氏体的精细结构及浮突形态。在浮突和腐蚀后的组织上都发现，Ｃｕ－Ｚｎ－Ａｌ合金中的贝氏体确是由亚片条和亚单元所组成，进而为贝氏体相变机制的深入研究提供了重要实验基础。在此基础上给出了Ｃｕ－Ｚｎ－Ａｌ合金中贝氏体的结构模型。     

Fe—C—Si—Mn合金中贝氏体表面浮突的精细结构

用扫描隧道显微镜对Ｆｅ－Ｃ－Ｓｉ－Ｍｎ合金中的下贝氏体浮突进行了观察研究。发现用透射显微镜观察到的最小结构单元－－亚单元是由更小的超亚单元组成的。超亚单元的浮突为“帐篷”型,而非不变平观应变型,表明它不是切变形成;超亚单元的浮突高度为６０－１４０ｎｍ,最大形状变型量约为０．２３,贝氏体的多层次结构以及合金元素Ｃ和Ｓｉ对它的影响可用激发形核－台阶生长机制来解释。     

扫描隧道显微镜研究Cu—Zn—Al合金中贝氏体及其浮突

用扫描隧道显微镜（ＳＴＭ）在大气中研究了Ｃｕ－２７．２Ｚｎ－４．７Ａｌ合金中贝氏体的精细结构及浮突形态。在浮突和腐蚀后的组织上都发现，Ｃｕ－Ｚｎ－Ａｌ合金中的贝氏体确是由亚片条和亚单元所组成。进而为贝氏体相变机制的深入研究提供了重要实验基础，在此基础上给出了Ｃｕ－Ｚｎ－Ａｌ合金中贝氏体的结构模型。     

贝氏体钢中贝氏体铁素体精细孪晶

用高分辨透射电子显微镜观察分析了贝氏体钢贝氏体铁素体的精细结构及其尺寸。观测指出，贝氏体铁素体的组织结构可分为三个层次：贝氏体条束或贝氏体片、亚片条和最小基本单元，或者分为四个层次：贝氏体条束或贝氏体片、亚片条、亚单元和最小基本单元。贝氏体铁素体条束由细小亚片条组成，这些亚片条多数是精细孪晶片条，它们宽度 为5．0－40nm。细小亚片条间存在孪晶取向关系。多数细小亚片条由大约5．0－25nm尺寸的基本单元组成。     

贝氏体铁素体精细结构孪晶及纳米结构

用高分辨电子显微镜观察分析贝氏体钢贝氏体铁素体精细结构及其尺寸的结果表明 ,上贝氏体铁素体亚片条间存在孪晶取向关系 ;下贝氏体铁素体内有孪晶 ;贝氏体铁素体条束由细小的亚片条组成 ,这些亚片条多数是精细孪晶细小片条。高分辨电镜 (HREM)准确地确定细小孪晶片条宽度在 2～ 30nm范围内。文中讨论了贝氏体铁素体精细孪晶形成机制     

钢中贝氏体组织形态和亚结构(二)

正3贝氏体组织中的亚结构由于贝氏体相变的过渡性特征,使得贝氏体的亚结构非常复杂。精细亚结构是指在电镜下所能分辨的贝氏体铁素体条片内部的细节,如亚片条、亚单元的形态、尺寸、界面结构以及贝氏体铁素体片条内部的位错、精细孪晶等。     

贝氏体和马氏体相变及应用的研究

系统总结了清华大学相变及复相新材料研究组近年来在贝氏体相变领域关键性的最新研究成果，包括三维巨型及纳米台阶存在的客观性和普遍性、台阶阶面的可动性、贝氏体片条的内部超精细结构、贝氏体浮突的特征及本质、贝氏体碳化物的来源及形成模型、马氏体浮突的扫描隧道显微镜（ＳＴＭ）及原子力显微镜（ＡＦＭ）研究；进一步论述贝氏体相变的激发形核－台阶长大（ＳＮＬＧ）机制，并用ＳＮＬＧ机制解释了贝氏体的多层次复杂亚结构；同时，还论述了空冷贝氏体／马氏体复相钢的工业应用。     

改善Mn—Ni—Mo钢大锻件机械性能的热处理方法

<正> 为了保证大锻件所必需的淬透性和达到要求的综合机械性能,通常采用含Cr、Ni、Mn、Mo和其他元素的合金钢,并且在淬火时采用快速冷却(水淬或油淬),力求保证沿锻件截面完全淬透到贝氏体。这时不希望钢内有铁索体和珠光体存在,因为这会使锻件机械性能降低。然而,据文献[1～3]报     

MICROSTRUCTURE AND REVERSE SHAPE MEMORY EFFECT IN A Cu-Zn-Al ALLOY

The bainite structure in a Cu-Zn-A1 alloy related to the reverse shape memory effect hasbeen observed by means of TEM.The reverse memory effect may be improved by up to oneorder of magnitude under applied constraint stress.The widespread propagation of bainite wasconfirmed to be the diffusion controlled shear process by the parabolic configuration of sideinterface of bainite plate and the twisting of intersected bainite plates.     

THE FAILURE MECHANISM OF REVERSE SHAPE MEMORYEFFECT IN A Cu-BASE ALLOY

1.IntroductionItiswellknownthatthereverseshapememoryeffect(RSME)isrelatedtobainitictransf0rmati0ninCu-baseshapememoryalloys(SMA)['l'].Thusthestructure0fbainite(a1)playsanimportantroleinthiseffect.Ref.I3]indicatesfurtherthatthereverseshapememoryeffectmaybeimprovedupt00neorder0fmagnitudeunderappliedconstraintstress-ThismeansthatRSMEunderanexternalstresshaJsabroadengineeringprospect.Inordertoelucidatethemechanism0fb0threverseshapememoryeffectandbainitictransformationinCu-basealloys,thispap…     

Twice reverse shape memory effect in CuZnAl shape memory alloy

The variations of the shape memory effects in the Cu-13Zn-15Al(mole fraction, %) alloy upon successive heating (the rate of heating is 5℃/min) have been studied by means of ρ-T curve , shape memory effect measurement, optical metallographical observation and X-ray diffraction. The first abnormal reverse shape memory effect occurs when the tested alloy is heated to the temperature below 320℃ ; when it is heated to the temperature between 320℃ and 450℃, the forward shape memory effect occurs; in the two stages, the shape of the sample remains the same as that in the furnace when it is taken out from the furnace and air-cooled; when the tested alloy is heated to the temperature above 450℃, the shape of the sample remains unchanged during heating, but the second reverse shape memory effect occurs after it is air-quenched.     

HIGH TEMPERATURE SHAPE MEMORY EFFECT AND PRE-DEFORMATION FOR Ti_(50) Ni_(13) Pd_(37) ALLOY

The dependence of high temperature shape memory effect on the pre-deformation tempera-ture of the Ti_(50)Ni_3Pd_(37) alloy has been studied.This alloy,of which the reverse transformationstart temperature on heating is 620 K,has both one-way and two-way shape memory effects.The maximum shape memory strain of the ahoy may be obtained under pre-deformation inthe range of 620 to 640 K.This seems to be related to the minimum recoverable strain energyemerged from the above mentioned temperature range.     

Ti-13at.-％Ni-37at.-％Pd记忆合金预形变与高温形状记忆效应SCIEI

本文着重地研究了Ti-13at.-％Ni-37at.-％Pd合金的高温形状记忆效应与预形变温度的关系.该合金A_s温度是620K,具有单程形状记忆效应和双程形状记忆效应。在620—640K温度预形变,可以得到最大的形状记忆应变,这与在此温区产生的最小可逆应变能有关。     

Temperature memory effect of Ni47Ti44Nb9 wide hysteresis shape memory alloy

The temperature memory effect (TME) phenomenon of Ni₄₇Ti₄₄Nb₉ wide hysteresis shape memory alloy was studied. It was found that TME occurred during the reverse transformation for the thermally-induced martensite (TIM) but not for the stress-induced martensite after incomplete transformation cycling. The reverse transformation temperature interval of TIM can be doubly broadened after 10 incomplete transformation cycles.     

Temperature memory effect of Ti50Ni30Cu20 (at.%) alloy

After the reverse thermal induced martensitic transformation process of shape memory alloy is arrested at a temperature between the reverse transformation start and finish temperatures (A_s and A_f), and then cooled to a temperature below M_f, a kinetic stop will occur in the next heat flow curve during the heating process. The kinetic stop is closely related to the arrested temperature. This phenomenon is called temperature memory effect (TME). TME of Ti₅₀Ni₃₀Cu₂₀ (at.%) shape memory alloy with phase transformation between B2 austenite and B19 martensite has been investigated by differential scanning calorimeter in this paper. The results indicate that TME of Ti₅₀Ni₃₀Cu₂₀ alloy only exists in the heating process.     

Effect of heat treatment on the transformation behavior and temperature memory effect in TiNiCu wires

The effect of heat treatment on the phase transformation behavior of TiNiCu shape memory alloy wires and the temperature memory effect in this alloy were investigated by the resistance method. These results showed that with increasing annealing temperature and annealing time, the phase transformation temperatures of TiNiCu wires were shifted to higher temperatures in the heating and cooling process. It was also found that incomplete thermal cycles, upon heating the TiNiCu wires, which were arrested at a temperature between the start and finish tem-peratures of the reverse martensite transformation, could induce a kinetic stop in the next complete thermal cycle. The kinetic stop tempera-ture was closely related to the previous arrested temperature. This phenomenon was defined as the temperature memory effect. The result of this study was consistent with the previous report on the phenomenon obtained using the differential scanning calorimetry method, indicating that temperature memory effect was a common phenomenon in shape memory alloys.     

时效对Ti─51％Ni形状记忆合金组织和相变行为的影响

用示差扫描热分析仪（ＤＳＣ）和光学显微镜研究了时效对Ｔｉ－５１ａｔ％Ｎｉ形状记忆合金组织和相变行为的影响。加热冷却时，该合金发生了Ｂ_２　Ｒ　Ｍ转变。给出了Ｒ、Ｍ相变温度、热滞、相变热与时效温度、时效时间的关系。Ｒ相的形态类似于上贝氏体或魏氏组织。析出物的形态呈针状交叉分布。