【作者】 张毅；

【导师】 井晓天；

【作者基本信息】 西安理工大学 ， 材料学， 2007， 硕士

【摘要】 形状记忆合金被誉为热驱动的功能材料,同时兼具传感功能,受到广泛重视。本文采用动态记忆效应测试、金相组织观察、X射线分析等方法,对Cu-Zn-Al合金的马氏体形貌和结构进行了研究,并探讨了不同的热处理工艺对微观组织和形状记忆效应的影响。结果表明:淬火保温温度对合金形状回复的影响非常明显,随着保温温度的升高,合金晶粒长大,Ms点不断升高。实验合金在600℃～750℃范围内淬火得到的组织中存在相当数量的α相,合金的形状回复率在800℃后趋于稳定并达到最大值。淬火生成的马氏体片界平直清晰,晶界无任何新相析出。800℃～900℃形状回复率趋于稳定没有明显下降。合金的形状记忆效应对淬火保温时间也较为敏感。800℃淬火保温随着时间的增加,合金的形状记忆效应是一个先增加再减小的过程。当淬火保温时间过短或过长都会损害合金的记忆性能,只有在适当的保温时间才具有较高形状记忆效应。合金在800℃淬火保温15min时得到最佳的形状记忆效果。在同一种处理工艺下,在马氏体状态所加预应变量,对形状记忆效应有明显影响。对于试验合金而言,存在一个临界的预变形量εL(ε=3.3%),当ε<ε_L时,形状记忆回复率随着预变形量的增大而增大;而当ε>ε_L时,形状记忆回复率又随着预变形量的增大而减小。淬火冷却介质不同,合金的记忆效应也有所不同。相变驱动力较大时,马氏体明显粗大,形状记忆效应明显提高。实验合金在室温下长期时效其记忆性能有小幅下降。在较低温区较短时间时效(100℃～150℃)合金的单向回复率有所提高。随着时效温度的提高(200℃～300℃),合金发生贝氏体相变,从而逐渐失去记忆性能。对于双向记忆性能而言,在低温时效(100℃～150℃)的过程中随着时效时间的延长记忆性能不断的衰减,随着时效温度的提高(200℃～300℃)同样发生贝氏体相变失去记忆性能。形状记忆训练可以使合金获得择优取向的马氏体,从而获得较高的、稳定的双程记忆效应,但同时使合金的单程记忆性能下降。随着热循环的进行,合金的单双向记忆性能都呈明显的下降趋势。更多还原

【Abstract】 As a functional material of heat-driven, the shape memory alloy which sensor function has been attached, received its extensive recognition. In this paper, morphology and structure of martensite are studied by means of optical microscope, XRD and so on, and the influence of different heat treatment on microstructure and shape memory effect has also been studied. The result is as follows:The quenching temperature has a notable influence on shape memory of alloy. The alloy grain growth increases and Ms is also continually increasing as well when the quenching temperature is higher and higher. This kind of alloy has a lot ofαphase in its microstructure when it be quenched at 600℃～750℃, while the shape memory effects reaches the peak value at 800℃.The martensite produced by quenching has a clear interface and there is no precipitation on the grain boundary. The Shape memory effect of alloy has not clear weakening when it is soaked at 800℃～900℃.Shape memory effect is very sensitive to quenching soaking time. Different soaking time has been continued at 800℃, the shape memory effect increases rapidly and then it has a mini-devaluation. The shape memory effect will decline if the soaking time is too long or too short. In order to obtain an excellent shape memory effect, the quenching soaking time should be appropriate. The alloy obtains the satisfied shape memory effect when it was soaked for 15 minutes at 800℃.The prestrain of alloy with same heat treatment technology has a notable influence on shape memory effect. Experimental alloy have a critical prestrain(ε=3.3%),the shape memory effect increases with the increase of prestrain whenε<ε_L, however, it would be weaken with the increase of prestrain whenε<ε_L.Shape memory effect is not same when quenching medium is different. A big phasetransformation driving force can gain coarse martensite and the shape memory effect has improved significantly.The shape memory effect shows a little downtrend when aging at room-temperature lasts for a long time. One-way recovery ratio of alloy shows an increase within 100℃～150℃in a short aging time. Bainite phase transformation will happen when the aging temperature(200～300℃) is high and then the alloy will lost the shape memory effect. The two-way shape memory recovery ratio of alloy shows a downtrend at 100℃～150℃. Bainite phase transformation will happen when the aging temperature(200～300℃) raises, thus the shape memory effect lost.This kind of alloy can obtain preferred orientation martensite by SEM so a stable two-way can be obtained, while one-way shape memory effect decline little by little. As the thermal cycling goes on, both one-way shape memory effects and two-way memory effects substantively show a downward trend.更多还原