【作者】 周丽花；

【导师】 戴品强；

【作者基本信息】 福州大学 ， 材料学， 2004， 硕士

【摘要】 本文研究了Fe-Mn-Si、Fe-Mn-Si-Cr-Ni及Fe-Mn-Si-C形状记忆合金化学成分、热处理工艺、显微组织结构、层错能和形状记忆效应的关系；研制Fe-Mn-Si-C形状记忆合金管接头，并分析管接头扩孔率、连接长度、管壁厚度对连接强度及其耐压性能的影响。结果表明：在Fe-Mn-Si合金中加入碳、铬、镍元素可以显著提高合金的形状记忆效应。适当的热处理工艺可以使合金获得最好的形状记忆效应。淬火温度对合金形状记忆效应有显著影响：合金700℃淬火后可得到最大的形状回复率；采用快速冷却能提高合金的形状回复率；实验合金预变形后加热到50℃，开始发生形状回复；50~150℃形状回复速度最快， 150℃以后合金回复率基本不发生变化。合金的形状回复率随着预变形量的增加而减小。用X射线衍射峰位移法测量合金在锻造态及不同淬火温度后的层错几率，发现Fe-Mn-Si-Cr-Ni、Fe-Mn-Si-C合金的层错几率随淬火温度的升高而升高，在600~700℃时达到最大，然后又随淬火温度的进一步升高而降低；Fe-Mn-Si合金的变化规律与之相反，且变化幅度很小。淬火温度对Fe-Mn-Si基合金层错几率的影响主要是由于铬、镍、碳等原子及淬火空位的偏聚而引起的。采用光学显微镜和透射电子显微镜观察合金经不同淬火温度及不同预变形量后的显微组织。研究表明，热诱发ε马氏体对合金的形状记忆效应具有双重作用，适量的热诱发ε马氏体有利于合金的形状记忆效应。淬火后合金中层错和马氏体形态对合金的形状记忆效应有一定的影响。低应力水平诱发的薄片状ε马氏体很容易发生ε→γ逆相变而消失，较高应力水平诱发的厚片状且相互交叉的ε马氏体，加热时不易回复。Fe-Mn-Si-C记忆合金制成的管接头具有很高的连接强度和良好的耐压性能；管接头的连接强度随着扩孔率、管壁厚度的增加而升高，但随着连接长度的增大而降低；加入碳元素并不降低合金的耐腐蚀性能。更多还原

【Abstract】 The influence of chemical component, heat treatment process, microstructure and stacking fault energy on shape memory effect of Fe-Mn-Si, Fe-Mn-Si-Cr-Ni and Fe-Mn-Si-C alloys was investigated. The coupler of Fe-Mn-Si-C alloys was developed and the influence of bearizing rate of coupler, connection length and thickness of pipe wall on the connection strength and pressure resistance was analyzed. The results show that the addition of carbon, chrome and nickel elements into Fe-Mn-Si alloys improves the shape memory effect of the alloys greatly; proper heat treatment process helps to achieve the best shape memory effect of alloys; quenching temperature affects shape memory effect of alloys significantly; the maximum shape recovery ratio is achieved in alloys quenched from 700℃.Rapid cooling process can improve the shape recovery ratio. When heated to 50℃, shape recovery takes place in alloys subjected to predeformation. The velocity of shape recovery reaches a maximum at the range of 50-150℃ and nearly remains stable with further increasing of quenching temperature. The shape recovery decreases with the increasing of predeformation amount. The stacking fault probability of alloys at forged state and quenched state was measured by X-ray diffraction peak displacement method. It is found that the stacking fault probability of Fe-Mn-Si-Cr-Ni and Fe-Mn-Si-C alloys firstly increases with the increasing of quenching temperature, reaches a maximum at the range of 600-700℃, and then decreases with further increasing of quenching temperature; the stacking fault probability of Fe-Mn-Si alloys varies contrarily and slightly compared with that of above both alloys. The aggregation of Cr, Ni, C atoms and quenched-in vacancies is responsible for the influence of quenching temperature on the stacking fault probability of alloys.The optical microscope and transmission electron microscope were used to observe the microstructure of alloys subjected to different predeformation and quenched from different temperature. It is found that heat inducedε-martensite has double effect on shape memory effect of alloys. Porper quantities of heat inducedε-martensite benefit shape memory effect of alloys. The morphologies of stacking fault and martensite in<WP=4>quenched alloys may affect shape memory effect of alloys. Low stress induced ε-martensite laminar plates are liable to disappear due to the inverse phase transformation of ε→γ. When heated, high stress induced ε-martensite plates that are larger and intersected are difficult to be recovered.The coupler maded of Fe-Mn-Si-C shape memory alloys has very high connection strength and good pressure resistance. The connection strength increases with the increasing of bearizing rate of coupler and thickness of pipe wall, but decreases with the increasing of connection length. The addition of carbon atom doesn’t reduce the corrosion resistance of alloys.更多还原