Ti50＋xPd30Ni20—x高温形状记忆合金的弹性行为

制备了三种Ti50 xPd30Ni20-x高温形状记忆合金,使用热分析测试了合金的相变温度,发现当Ti原子分数偏离50％时,合金的相变温度随Ti成分的升高而降低,并对这种合金的力学性能进行了测试,合金在奥氏体转变结束温度以上变形仍具有形状记忆效应,应力诱发的马氏体在应力去除后不能恢复到奥氏体,研究了这种合金在不同的重复加载条件下的弹性行为,实验表明,弹性回线的形状特征与加载历程有关,在奥氏体转变结束温度附近加载可以获得完全的线性伪弹性;而对于处于稳定单相的试样,在重复加载的条件下也可以获得弹性滞后回线。     

Ti50.6Ni合金弹簧超弹性行为研究

研究了试验温度、退火温度（ Ｔｈ） 及应力—应变循环对Ｔｉ５０ ．６Ｎｉ 合金弹簧超弹性（ＳＥ） 行为的影响。结果表明，冷拔态Ｔｉ５０ ．６Ｎｉ 合金中温退火后，热循环相变类型为Ａ→Ｒ→Ｍ←——— ，组织呈纤维状。该合金弹簧经６２３ ～７７３Ｋ 退火后，室温下可获得ＳＥ。随试验温度升高，弹簧刚度增加。Ｔｈ≥８２３Ｋ时，ＳＥ特性变坏。应力—应变循环初期，弹簧的切应力、切应变恢复率急剧衰减，随循环次数增加，衰减变慢。预循环训练可增强ＴｉＮｉ 合金弹簧超弹性的稳定性。     

Ti—50.6ni合金弹簧超弹性行为研究

研究了试验温度、退火温度（Ｔｈ）及应力一应变循环对Ｔｉ－５０．６Ｎｉ合金弹簧超弹性（ＳＥ）行为的影响。结果表明，冷技态Ｔｉ－５０．６Ｎｉ合金中退火后，热循环相变类型为Ａ→Ｒ→Ｍ，组织吾纤维状。该合金弹簧经６２３～７７３Ｋ退火后，室温下可获得ＳＥ。随试验温度升高，弹簧刚度增加。Ｔｈ≥８２３Ｋ时，ＳＥ特性变坏。应力一应变循环初期，弹簧的切应力、切应变恢复率急剧衰减，随循环次数增加，衰减变慢。预循环训练     

超弹性NiTi合金相变棘轮行为的实验研究

超弹性NiTi合金在应力控制循环载荷下会产生峰值应变和谷值应变的循环累积--相变棘轮行为.室温实验表明,峰值应变和谷值应变的演化规律与加载应力水平和加载波形密切相关;同时,在循环加载过程中,随着循环周次的增加,奥氏体名义弹性模量减小,马氏体名义弹性模量增大,奥氏体向马氏体转变的名义开始应力下降,耗散能降低,并在一定的循环次数下趋于一个稳定值.研究得到了一些有助于后续建立超弹性循环本构模型的结论.     

应变速率对TiNi形状记忆合金压缩力学行为的影响

考察了中温时效处理后的Ti-50.9%Ni(摩尔分数)合金在实验温度为20℃,不同应变速率下的轴向压缩应力-应变力学行为.实验结果表明:随着应变速率的增加,合金的应力诱发马氏体相变临界应力逐渐增加,相变平台逐步消失,卸载后的残余应变减小,加载-卸载变形曲线的应力(应变)滞后也减小;在较高加载速率下,合金表现出类线性超弹性变形行为,可获得高达4.5%的类线性超弹性.     

NiTi(Fe)合金的预相变和伪弹性

研究了NiTi(Fe)合金在不同温度下的伪弹性行为,并在加应力的条件下作了相应的x光衍射和电子衍射研究,获得如下结果:(1)在N-I相变点T_I以上,应力应变曲线已出现回线面积较小的超弹型回线,这是由于应力感生无公度相引起的.(2)在R_s≤T相似文献   

EXPERMENTAL STUDY ON TRANSFORMATION RATCHETING OF SUPERELASTIC NITI ALLOY

超弹性NiTi合金在应力控制循环载荷下会产生峰值应变和谷值应变的循环 累积-相变棘轮行为. 室温实验表明, 峰值应变和谷值应变的演化规 律与加载应力水平和加载波形密切相关; 同时, 在循环加载过程中, 随着 循环周次的增加, 奥氏体名义弹性模量减小, 马氏体名义弹性模量增大, 奥 氏体向马氏体转变的名义开始应力下降, 耗散能降低, 并在一定的循环次数 下趋于一个稳定值. 研究得到了一些有助于后续建立超弹性循环本构模型 的结论.     

Ti-Ni-Co(Cr,V)超弹性合金的相变和形变特性

用示差扫描量热仪和拉伸试验对比研究了Ti-50.8Ni、Ti-49.8Ni-1.0Co、Ti-50.8Ni-0.5V和Ti-50.8Ni-0.3Cr(原子分数%)超弹性合金的相变和形变特性.结果表明,冷却加热时,400 ℃退火态Ti-50.8Ni-0.3Cr合金发生AR(A-母相,R-R相)一阶段可逆相变,其余3合金发生ARM(M-马氏体)两阶段可逆相变.以Co取代Ni,以Cr、V取代Ti后,Ti-Ni合金的R、M相变温度和相变热降低,M相变热滞增加,R相变热滞变化不大.4种合金室温下皆显示超弹性,加入1.0%Co和0.5%V后,合金的超弹性应力分别减小了130MPa和85MPa,超弹性应变分别减小了1.8和2.4;加入0.3%Cr后,合金的超弹性应力增加了147MPa,超弹性应变减小了2.9;Co、Cr、V的加入使合金的应力-应变回线面积减小.     

哈斯勒合金Ni_(46)Cu_4Mn_(38)Sn_(12)的相变应变与磁感生应变

通过结构、磁性以及应变测量,研究哈斯勒合金Ni46Cu4Mn38Sn12在马氏体相变过程中的相变应变与磁感生应变。结果表明:样品在马氏体相变过程中表现出一个接近0.12%的相变应变,几乎是目前研究所报道的三元哈斯勒合金Ni-Mn-Sn相变应变的3倍;此外,在等温条件下,通过外加磁场的诱导,获得了该样品在反马氏体相变起始温度点(284 K)的一个大的磁感生应变,这种行为可归结为马氏体与奥氏体相之间界面的磁弹耦合。     

Ni—Ti—Nb宽滞后形状记忆合金的形变诱发马氏体相变及其可逆性

用透射电镜、高分辨电镜、不同温度下的拉伸试验以及电阻率－温度曲线测试研究了Ｎｉ－Ｔｉ－Ｎｂ合金形变诱发马氏体相变及其可逆性，分析了形变诱发马氏体的稳定性和可逆性与其变体界面结构之间的关系。结果表明，Ｎｉ－Ｔｉ－Ｎｂ合金在Ｍｓ－Ｍｓ＾σ温度区间加应力时发生应力诱发马氏体相变，而在Ｍｓ＾σ以上温度加应力时，发生应变诱发马氏体相变。形变对Ｎｉ－Ｔｉ－Ｎｂ合金的应力诱发马氏体界面结构有明显影响，随着拉伸变     

MICROSTRUCTURE AND COMPRESSIVE PROPERTIES OFTi_(50)Al_(48)Mn_2 AND Ti_(50)Al_(48)Cr_2

The microstructure and compressive properties of Ti_(500Al_(48)Mn_2and Ti_(50)Al_(48)Cr_2 alloys are studied in this paper Existence of αx y transforntation in TiAl alloys is confirnted by metallographic examincttion,the transformation temperatuses of Ti_(50)Al_(48)Mn_2 and Ti_(500Al_(48)Cr_2,are 1375and 1373C respeclively,After treating withic x y phase field,themicrostructure of alloys consists of lamellar zones(L)and bulk y_p.,The vohme ratio of L/y_p inctrases with increasing solution treatnient temperature.The third alloying ele-ments of Mn and Cr distribute perfentially over αphase at solution treatment tempera-tures and result in that α_2 and γ lamellae become thicker.The yield strength of Ti_(50)Al_(48)Mn_2 and Ti_(500Al_(48)Cr_2 alloys decreases and the compressibllity increases with in-creasing γ_p volume fraction.     

Ti50＋x Pd30Ni20—x合金的相变温度

使用热分析和高温X射线研究了Ti50-xPd30Ni20-x合金相变温度的变化情况,发现当Ti的原子分数偏离50%时,合金的相变温度随Ti成分的升高而降低,处于固溶处理的合金的相变温度最高,合金经过轧制及回复处理后,相变温度会降低。分析认为,这与合金内的缺陷、内应力和析出物密切相关。     

固溶态Ti（50＋x）Pd30Ni（20—x）合金中的相变特征

Ti(50 x)Pd30Ni(20-x)合金在固溶处理之后存在2次相变，使用DSC，XRD，DMTA以及TEM等手段研究了这种相变，结果表明，低温马氏体为单斜的B19'相，而高温母相则为体心立方的B2相，在相变过程中点阵的切变以正交的B19马氏体相作为过渡。低温马氏体的弹性模量比高温奥氏体的弹性模量高10GPa。随着频率减小，阻尼增大。在较高的频率下，弹性模量曲线和阻尼曲线对于过渡相的存在反映不明显，室温下马氏体为细狭的板条状，当温度达773K时，合金中有明显的析出物产生。     

时效处理对TiNiCr形状记忆合金相变的影响

利用差示扫描量热仪(DSC)、扫描电镜(SEM)和D/max2500PC全自动X射线衍射仪研究了不同时效处理制度下TiNiCr合金相变温度的变化规律.结果表明,该合金随着时效温度增加,逆马氏体相变点As、Af上升,但当时效温度高于700℃时,相变点As、Af降低.该合金在冷却过程中经历了B2→R→B19′两阶段一级相变.通过SEM和XRD衍射研究表明,该合金经时效处理产生了Ti3Ni4析出相诱发了R相变.     

Transformation behavior and shape memory effect of Ti50-xNi48Fe2Nbx alloys by aging treatment

The influence of aging treatment on transformation behavior and shape memory of the Ti50-xNi48Fe2Nbx(x=0,0.6,0.8,1.0,and 1.2)alloys was investigated using differential scanning calorimeter(DSC),mechanical drawing machine,and microhardness tester in this paper.It is indicated that the aging treatment has a significant effect on the phase transformation temperatures(Ms,Mf,Mp,As,Af,and Ap)and microhardness of the samples.The phase transformation temperatures are found to decrease initially with the increasing aging temperature from 300 to 500 ℃ and increase with further increase of the aging temperature.The aging treatment at intermediate temperature between 400 and 500 ℃ results in an improved shape memory effect.In addition,the highest microhardness value is also obtained.     

P-phase precipitation and its effect on martensitic transformation in (Ni,Pt)Ti shape memory alloys

A new precipitate phase named P-phase has recently been identified in (Ni,Pt)Ti high temperature shape memory alloys. In order to understand the roles played by the fine coherent P-phase precipitates in determining the martensitic transformation temperature (M_s), strength of the B2 matrix phase, dimensional stability and shape memory effect of the alloys, a phase field model of P-phase precipitation is developed. Model inputs, including lattice parameters, precipitate-matrix orientation relationship, elastic constants and free energy data, are obtained from experimental characterization, ab initio calculations and thermodynamic databases. Through computer simulations, the shape and spatial distribution of the P-phase precipitates, as well as the compositional and stress fields around them, are quantitatively determined. On this basis, the elastic interaction energy between the P-phase precipitates and a martenstic nucleus is calculated. It is found that both the chemical non-uniformity and stress field associated with the P-phase precipitates are in favor of the martensitic transformation. Their relative contributions to the increase in M_s temperature are quantified as a function of aging time and the result seems to agree with the experimental measurements. The shape and spatial distribution of the P-phase precipitates predicted by the simulations also agree well with experimental observations.     

Estimation of Transformation Temperatures in Ti–Ni–Pd Shape Memory Alloys

The present study focused on estimating the complex nonlinear relationship between the composition and phase transformation temperatures of Ti–Ni–Pd shape memory alloys by artificial neural networks (ANN). The ANN models were developed by using the experimental data of Ti–Ni–Pd alloys. It was found that the predictions are in good agreement with the trained and unseen test data of existing alloys. The developed model was able to simulate new virtual alloys to quantitatively estimate the effect of Ti, Ni, and Pd on transformation temperatures. The transformation temperature behavior of these virtual alloys is validated by conducting new experiments on the Ti–rich thin film that was deposited using multi target sputtering equipment. The transformation behavior of the film was measured by varying the composition with the help of aging treatment. The predicted trend of transformational temperatures was explained with the help of experimental results.     

Thermodynamics of martensite transformation hysteresis in Ni-Ti shape memory alloys

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Microstructures and Properties of W-Ti Alloys Prepared Under Different Cooling Conditions

W-(10 to 15) wt.% Ti alloys were sintered at 1400 or 1500 °C and cooled under different cooling conditions. The microstructures and properties of W-Ti alloys were affected by the cooling conditions. XRD, SEM, EBSD, and TEM were carried out to investigate the effects of cooling conditions and sintering temperature on the microstructures of W-Ti alloys. The nanohardness and elastic modulus of the alloys were also investigated. The results showed that when the temperature was 1500 °C, the content of Ti-rich phase in W-(10 to 15) wt.% Ti alloys decreased obviously with the increase of cooling rate (the average cooling rate of furnace cooling, air cooling and water cooling was 0.2, 10, and 280 °C/s, respectively). For the W-10 wt.% Ti alloy, the content decreased from 20.5 to 9.7%, and the grain size decreased from 2.33 to 0.67 μm. When the temperature decreased to 1400 °C, the grain size was also decreased sharply with the increase of cooling rate, but there was a little change in the microstructure. Meanwhile, the grain sizes were smaller than those of the alloys sintered at 1500 °C. The nanohardness and elastic modulus increased with the increase of cooling rate, and the alloys sintered at different temperatures had different nanohardness and elastic modulus which depended on the cooling conditions. Sintering at a proper temperature and then cooling at a certain cooling condition was a useful method to fabricate alloy with less Ti-rich phase and high properties.     

铝合金搅拌摩擦焊管液压胀形性能及变形规律

采用热模拟实验研究了Ni50Ti46-xAl4Hfx (x=0～6,at％)合金的微观组织特点和高温变形行为.合金由基体相NiTi和第二相Ti2Ni组成.Hf全部溶解在基体相和第二相中,并且促进了第二相的析出,显著提高了合金的高温强度.Ni-Ti-Al-Hf合金在700～800℃下变形行为的研究表明:合金具有良好的高温压缩性能,流变应力随着应变速率的减小或变形温度的增加而降低,其高温变形行为符合温度补偿幂规律描述.Hf的添加使合金的应力指数(n)和变形激活能(Q)上升,这主要是由于Hf的固溶强化、促进Ti2Ni相析出强化和高温稳定性造成的.