共查询到19条相似文献,搜索用时 171 毫秒
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采用差示扫描量热仪(DSC),分析了X60管线钢在加热与冷却过程中的相变温度.结果表明:在冷却时DSC曲线上出现三个峰值,除先共析铁素体析出和珠光体转变外,还有铌或钒的碳化物析出;相变温度随冷却速度的增大而降低;在加热至950℃时,DSC曲线上出现二个峰值,除先共析铁素体溶解和奥氏体转变外,没有明显的铌或钒的碳化物峰溶入奥氏体峰. 相似文献
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采用差示扫描量热仪研究了Ti50Ni35Cu15以及Ti50Ni45Cu5(摩尔分数,%)形状记忆合金的温度记忆效应.结果表明:温度记忆效应仅在Ti-Ni-Cu合金的逆转变加热过程出现,在单斜结构马氏体与母相逆相变(B19'→B2)及正交结构马氏体与母相逆相变(B19→B2)过程中均能发生温度记忆效应;在随后的完全循环过程中,温度记忆记忆效应不再出现,DSC相变曲线又"恢复"到其原始形态;而在马氏体相变冷却过程中未发现温度记忆效应.分析表明,不完全相变过程中的弹性能再分布是可能的温度记忆效应机制. 相似文献
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Ti-Ni形状记忆合金多阶段可逆相变的类型及其演化过程 总被引:5,自引:0,他引:5
用示差扫描量热仪(DSC)和部分热循环分析法研究了350-800℃退火态和300-500℃时效态Ti-(50.2-50.8)Ni(原子分数,%)形状记忆合金多阶段可逆相变的类型及其演化过程.结果表明,这些合金发生R和马氏体两种可逆相变,相变可以一阶段完成,也可以多阶段完成.时效态合金的相变比退火态复杂,时效温度越低相变越复杂.若用DSC曲线上冷却相变峰数/加热相变峰数表示相变类型,则退火态和时效态合金冷却/加热时可以发生1/1,2/1,2/2,3/2和3/3等类型的相变.给出了各类相变发生的热处理工艺.多阶段可逆相变是一个渐变过程,在冷却相变峰的温度区间进行部分热循环时,随冷却停止(加热开始)温度降低,逆相变峰温度降低. 相似文献
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TiNi合金不完全相变的温度记忆效应 总被引:3,自引:0,他引:3
通过示差扫描量热分析(DSC)研究了预应变及约束条件下TiNi形状记忆合金的温度记忆效应.结果表明,通过变形约束手段,可以大大拓宽TiNi合金的相变温度区间,使得TiNi合金的温度记忆效应能够在一个非常大的温度范围内发挥作用;同时,变形并约束后TiNi合金的温度记忆效应比自由态TiNi合金的温度记忆效应更加准确.分析表明,马氏体与母相界面处的位错以及界面处的弹性自适应过程是可能的温度记忆效应机制。 相似文献
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采用示差扫描量热仪(DSC)、拉伸试验及透射电镜研究了不同矫直温度对Ti-50.8Ni超弹性合金丝材相变特性、超弹性及微观结构的影响。结果表明,冷矫态合金丝材冷却/加热时的相变类型为A→M/M→A,而温矫态及热矫态合金丝材冷却/加热时发生A→R→M/M→A(A―母相,R―R相,M―马氏体)型相变;冷矫态合金丝材组织择优取向性强,位错密度高,亚晶界弯曲模糊;而热矫态合金丝材缺陷密度最低,亚晶界平直清晰,超弹性最好。分析认为,应力、位错密度对Ti-50.8Ni超弹性合金丝材的相变特性及超弹性有重要的影响。 相似文献
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WANGZhiguo ZUXiaotao 《稀有金属(英文版)》2004,23(3):250-254
Two-way shape memory effect (TWSME) was induced into the TiNi shape memory alloys (SMAs) spring by thermomechanical training after annealing treatment, which has promising application in micro-actuating fields. The TWSME spring can contract upon heating and extend upon cooling. The results show that there is an increase of the recovery ratio up to a maximum TWSME of 45%. During the training procedure, transformation temperatures and hysteresis were measured by different scanning calorimetry (DSC). The results show that As (reverse transformation start temperature) and Af (reverse transformation fmish temperature) shift to lower temperature after training. The intervals of ArAs and Ms-Mf (Ms and Mf are the martensite start and finish temperatures, respectively) increase and the heat of transformation decreases after training. The electrothermal driving characteristics of the TWSME springs were also investigated with alternating current density of 3.2-14.7A/mm^2. It is found that the time response and the maximum contraction ratio greatly depend on the magnitude of the electrical current density. 相似文献
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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. 相似文献
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The two-way shape memory effect(TWSME) in a Ti36 Ni49 Hf15 high temperature shape memory alloy (SMA) was systematically studied by bending tests. In the TiNiHf alloy, the martensite deformation is an effective method to get two-way shape memory effect even with a small deformation strain. The results indicate that the internal stress field formed by the bending deformation is in the direction of the preferentially oriented martensite variants formed during the bending deformation. Upon cooling the preferentially oriented martensite variants form under such an oriented stress field, which should be responsible for the generation of the two-way shape memory effect.Proper training process benefits the formation of the oriented stress field, resulting in the improvement of the twoway shape memory effect. A maximum TWSME of 0.88% is obtained in the present alloy. 相似文献
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TiNiCu形状记忆合金薄带凭借其窄相变滞后、优异的形状记忆效应与超弹性、良好的热循环稳定性成为一种很有前途的微驱动器材料。本文全面阐述了国内外在TiNiCu薄带研究方面的最新进展,主要包括晶化行为、显微组织、马氏体相变行为、形状记忆效应与超弹性,重点介绍了热处理工艺-显微组织-性能之间的内在联系,探讨了TiNiCu薄带今后的研究重点 相似文献
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Ti49.4Ni50.6超弹性弹簧的相变和形变特性 总被引:13,自引:2,他引:13
用示差扫描量热仪、拉伸实验和应力-应变循环实验系统研究了退火温度、变形温度以及热循环和室温应力-应变循环对Ti49.4Ni50.6超弹性(SE)弹簧的相变和形变特性的影响。冷加工加中温退火态Ti49.4Ni50.6合金冷却→←加热时的相变类型为母相B2→←R相→←马氏体B19′。随退火温度升高,马氏体转变温度升高,R相转变温度降低。623-773K退火态Ti49.4Ni50.6弹簧室温下可获得SE特性,随变形温度升高,SE弹簧剐度增加;当退火温度超过823K后,SE持性变差。热循环时SE弹簧的切变量取值越小,其应变恢复率越高。预循环训练可增强SE的稳定性。 相似文献
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TiNiCu films were deposited on a (100) type Si substrates by co-sputtering of TiNi and Cu targets at room temperature, and then post-annealed at 450 °C for crystallization. Significant surface relief due to martensitic transformation occurred on the film surface after cooling, and variations in surface relief morphology (the size and density of martensite crystals) have been quantified with atomic force microscopy. Energy dispersive X-ray analysis showed that the surface relief morphological difference in the TiNiCu films is due to the change in composition. It was proposed that the crystallization of the amorphous thin film during annealing behaved differently with chemical composition, which in turn induced fluctuations in phase transformation temperatures at various regions, as confirmed by differential scanning calorimeter measurements. 相似文献
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Cu-11.19Al-6.43Mn合金的形状记忆效应 总被引:3,自引:0,他引:3
测试了Cu-11.19Al-6.43Mn合金的形状记忆效应,研究了预变形程度、恢复温度和训练次数对该合金的单向和双向形状记忆效应的影响。结果表明:该合金有一个能完全恢复的最大预变形程度εm,它随恢复温度的提高而增大,其最大值约为4.5%;合金的双向记忆效应随训练次数增加而增大。在适当的训练次数和训练温度下,其最大的冷却和加热时的开头恢复量之比值约为30%。 相似文献