PHASE TRANSFORMATIONS IN RAPIDLY SOLIDIFIED TiNi SHAPE MEMORY ALLOYS

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Zr对Cu—Zn—Al形状记忆合金相变的影响

采用示差扫描热分析(DSC)、X射线衍射及透射电镜,研究了Zr对Cu-Zn-Al合金高温相变、马氏体正逆转变以及形状记忆效应的影响。结果表明,添加Zr0.35wt-％时,能有效地抑制α,γ相析出,促进β_2→DO_3→18RM转变。(M_s-M_f)及(A_s-A_f)温度区间较窄,马氏体相变激活能最低,马氏体变体间界面的可动性好,形状记忆效应最佳。     

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.     

Cu—Zn—Al合金逆形状记忆组织的电镜观察

用透射电镜观察了Cu-Zn-Al合金中逆形状记忆的贝氏体组织。在外加约束应力作用下,逆记忆量可以提高一个数量级,贝氏体片侧相界面的抛物线轮廓和贝氏体片交叉曲折的现象说明了贝氏体展宽是扩散控制的切变过程。     

QUANTITATIVE CHARACTERIZATION OF STRESS-STRAIN HYSTERESIS LOOPS OF Cu-Zn-Al SHAPE MEMORY ALLOY

1. IntroductionAs a smart material, shape memory alloys (SMAs) have found many applications dueto their special shape memory characteristics[1--5]. Typical such alloys are TiNt, TiNibased and Cu-based alloys. It is often importallt to know their st ress- st r al n- t e mp erat urerelations before suitable designs can be made for particular applicationsI6---'2]. However, thest ress- strain- t emperat ure relations of S M As are nonli near and have bys teresis [ 1 o -- 15]. Andthe shape of…     

镍钛形状记忆合金获得优良记忆的工艺研究

采用正交试验法，研究了等原子比Ti-Ni形状记忆合金获得优良记忆效应的工艺措施，并分析了获得优良记忆效应的可能原因。     

多晶Cu-Zn-Al合金变形过程中马氏体的精细结构变化SCIEI

本文利用透射电子显微镜研究了多晶Cu-Zn-Al形状记忆合金在马氏体状态的变形过程中,其精细结构的变化。结果表明:在变形的初期阶段,变形通过变体的再取向实现,但再取向常有不完全性,而且再取向后,原先变体间的界面依然存在。变形量较大时,马氏体中出现大量的孪晶,孪晶面为(001)。在局部区域出现位错。这时马氏体失去热弹性,记忆效应被破坏。     

INFLUENCE OF PROCESSING ON SHAPE MEMORY EFFECT OF Fe-Mn-Si-Ni-C-RE SHAPE MEMORY ALLOY

Effect of carbon, compound RE, quenching temperature, pre-strain and recovery temperature on shape memory effect (SME) of Fe-Mn-Si-Ni-C-RE shape memory alloy was studied by bent measurement, thermal cycle training, SEM etc. It was shown that the grains of alloys addition with compound RE became finer and SME increased evidently. SME of the alloy was weakening gradually as carbon content increased under small strain (3%). But in the condition of large strain (more than 6%), SME of the alloy whose carbon content range from 0.1% to 0.12% showed small decreasing range, especially of alloy with the addition of compound RE. Results were also indicated that SME was improved by increasing quenching temperature (>1000℃). The amount of thermal induced martensite increased and the relative shape recovery ratio could be increased to more than 40% after 3-4 times thermal training. The relative shape recovery ratio decreased evidently depending on rising of pre-strain. Furthermore, because speed of martensite transi     

IN SITU METALLOGRAPHIC OBSERVAION OF THERMAL CYCLING EFFECTS ON PHASE TRANSFORMATION IN Cu-Zn-Al SHAPE MEMORY ALLOY

1.IntroductionTheproperties0fshapememoryalloys(SMA)aredegradedt0differentdegreesbyage-ing,thermalcycling,stresscycling0rprestrain.Thedegradation0fshapememoryeffecthasbeenstudied[1-6]ands0mepr0blemsaren0wunderstoodandthishasallowedsomedevel0pmentsinthepracticalusage0fCu-Zn-AlSMA.H0wever,theunstabletransf0rma-tiontemperaturesandthestabilization0fthermalmartensitesduringthermalcyclinghaveseriouslyrestraineditsprogressinusageandithasbec0meurgenttos0lvetheremainingproblems-Frommanyrecentstudies…     

STABILITIY OF MARTENSITE IN Cu-Zn-Al SHAPE MEMORY ALLOY AFTER DIRECT OR STEPPED QUENCHING

The stability of thermoelastic martensite in a Cu-14.84 wt-％Zn-7.75 wt-％Al shape mem-ory alloy with M_s=106°C after direct quenching or stepped quenching has been investigatedby using TEM,X-ray diffroctometer and double electric bridge instrument.The martensiteaged for about 3 h at room temperature after either direct quenching or stepped quenching(150°C,2 rain)is the M18R structure.The martensite just directly quenched is not so stable,both its certain diffraction peaks and specific electric resistivity,change with aging at roomtemperature;whereas it is stable after stepped quenching(150°C.2 min),and its diffractionpeaks and specific electric resistivity change no more with aging at room temperature.Theabove mentioned results seem to be explained by the martensite reordering.     

形状记忆合金的应用现状

形状记忆合金是二十年代发展起来的一种新型工程材料，目前已得到广泛的应用。本文介绍了它在航天航空、能源、建筑、汽车、机器人等领域中的应用现状。     

不锈钢型形状记忆合金记忆性能的影响因素

通过对不同Co含量不锈钢型形状记忆合金材料经不同热处理后的记忆性能变化及“训练”对合金形状回复率影响的研究发现,随淬火温度的升高,合金记忆回复率η随之提高,但温度过高,导致基体软化产生永久变形,使记忆回复率η又下降,降低Co元素含量并未对合金记忆回复率η产生明显不利的影响,提高训练次数,合金的记忆回复率η也随之提高。     

SUPERPLASTICITY OF A RAPIDLY SOLIDIFIED AI-Li ALLOY

A rapidly solidified microcrystalline Al-Li-Cu-Mg-Zr alloy and its superplasicity have beeninvestigated.An optimum tensile elongation of 585% was obtained at 540℃ and strain rate1.67×10~(-2)s~(-1).The superplastic Al-Li alloy is manufaetured using thermomechanical pro-cessing:solution,overaging,warm rolling and recrystallization.Microstructural changes inthermomechanical processing and cavitation occurred during superplastic deformation havebeen observed.The superplastic failure of alloy may be caused mainly by nucleation andgrowth of cavities as well as the linkage around grains.     

MICROSTRUCTURE OF A RAPIDLY SOLIDIFIED Fe-C-Sn ALLOY

The microstructure of a laser-melted Fe-4% C-10% Sn alloy has been studied.Anon-crystalline phase was found in the upper part of the laser-melted zone:At the bottom ofthe melted zone,however,the microcrystalline zone which consists of α-Fe and a bet phasewas observed.Fine twinning martensite exists in the other area of the melted zone.     

Cu-Zn-Al形状记忆合金直接淬火和分级淬火后马氏体稳定性的研究SCIEI

用透射电镜,X射线衍射仪和电阻法研究了Cu-14.84wt-％Zn-7.75wt-％Al形状记忆合金在直接淬火和分级淬火后马氏体的稳定性。试验结果表明,直接淬火和分级淬火(150℃,2min)后于室温时效约3h的马氏体均为M18R结构,但刚直接淬火后马氏体并不稳定,其某些衍射峰位置和电阻率均随室温时效而变化;而分级淬火(150℃,2min)后马氏体是稳定的,其所有衍射峰位置和电阻率几乎不随室温时效而变化。上述结果可用“马氏体再有序化机制”解释。     

OXIDE FILM ON EQUIATOMIC TiNi SHAPE MEMORY ALLOY

１ＩＮＴＲＯＤＵＣＴＩＯＮＥｑｕｉａｔｏｍｉｃＴｉＮｉｓｈａｐｅｍｅｍｏｒｙａｌｏｙ（ＳＭＡ）ｉｓａｎｏｖｅｌａｎｄｐｒｏｍｉｓｉｎｇｂｉｏｍａｔｅｒｉａｌｄｕｅｔｏｉｔｓｕｎｉｑｕｅａｎｄｅｘｃｅｌｅｎｔｓｈａｐｅｍｅｍｏｒｙｅｆｅｃｔａｎｄｓｕｐ...     

PHASE TRANSFORMATION IN RAPIDLY SOLIDIFIED AI-Cu-Fe ALLOY

By means of rapid solidification, two Al_(65)Cu_(20)Fe_(15) powders were prepared with water and liquid N_2 as the respective cooling agent. Both powders are composed of a qnasicrystalline icosahedral phase and a crystalline hexagonal phase, with the water-cooled alloy having a higher crystalline phase content. In the isothermal an nealing process, the crystalline phase in the water-quenched alloy begins to decrease at 500℃ and then disap pears at 600～700℃. At about 800℃, new crystalline phases form, and at 900℃, the quasicrystalline phase disappears. Conversely, in the liquid N_2 quenched alloy, the quasicrystalline phase starts to decrease at about 500℃. and the hexagonal phase decomposes into new crystalline phases. At 700～800℃, the quasicrystalline phase disappears. For the water-cooled sample, the quenching at 100～200C makes the crystalline to quasicrystalline phase transformation start at a lower temperature and the crystallization of the quasicrystal occur at a higher temperature. For the liquid N_2 quenched alloy, the quenching at 100～400℃, did not affect its phase transformation at high temperature.     

快速凝固Fe—C—Sn合金的显微组织

研究了经激光表面熔化处理的Fe-4％C-10％Sn合金的显微组织,发现在激光熔化区上部存在一种非晶相,而在其底部存在由α-Fe和一种bct相组成的显微组织,在熔化区其它区域存在含细小孪晶的马氏体。     

MICROSTRUCTURE OF RAPIDLY SOLIDIFIED TiAl ALLOY POWDER

The rapidly solidified powder of Ti-34Al-2Mn alloy was obtained by means of ultrasonicgas atomisation (USGA) technique.The tupical size of the powder is 27 μm.X-ray diffractionresults show that the powder consists of major α_2-phase and minor γ-phase.Under opticalmicroscope both equiaxed and dendritical microstructure features were observed on RS pow-der sections.After annealing at 900 ℃/for 2 h in vacuum,most of α_2-phase transforms intoγ-phase,resulting in refinement of structure.     

快速凝固TiAl基合金微晶的显微组织

用气体雾化方法制备了Ti-34Al-2Mn合金的微晶粉末,粉末典型粒度为27μm。X射线衍射结果表明,快冷态的粉末主要由α_2相和少量γ相组成。金相组织显示出等轴块状晶粒和树枝状结晶两种形态。经900℃,2h真空退火后,大部分α_2相转变成γ相,使原来的组织更加细化。