南京航空航天大学硕士学位论文原位自生碳化物颗粒增强Fe-Mn-Si基形状记忆合金及性能研究姓名：王河廷申请学位级别：硕士专业：材料加工工程指导教师：沈以赴20080301南京航空航天大学硕士学位论文摘要形状记忆合金是最具实用价值金属功能材料之一，Fe-Mn-Si基合金具有价格低廉、工艺简单等一系列优点。
但该系合金的形状回复率不高，耐蚀性能较差限制了其应用范围的进一步扩大。
本文通过优化合金成分设计，对原位自生碳化物颗粒增强Fe-Mn-Si基合金形状记忆效应及其相关性能进行了研究。
通过添加适量Nb，V，Ti，RE(Ce)等合金元素，设计了八种典型成分的Fe-Mn-Si基形状记忆合金，并用原位自生法制备出了碳化物颗粒弥散分布增强的Fe-Mn-Si基合金。
采用金相显微镜、扫描电镜、X射线衍射仪等研究了合金的显微组织及物相成分。
固溶态合金基体主要为奥氏体及少量热诱发ε马氏体，生成适量的热诱发马氏体对合金形状记忆效应有利。
随着预变形量增大，合金组织中应力诱发ε马氏体开始增多，由原来的单一方向ε马氏体变成交叉方向马氏体。
采用拉伸变形法，研究了不同工艺参数、不同成分合金的形状记忆效应。
结果表明，固溶态合金在变形前于一定的温度（750℃）进行时效处理（250min）能有效提高合金的形状记忆效应。
随时效处理温度的升高，合金形状回复率缓慢提高，在750℃下达到最大，之后开始下降。
合金的形状回复率随着预变形量的增大而减小，在预变形为2％时达到最大值，其中成分为Fe-14.0Mn-6.0Si-9.0Cr-5.0Ni-0.83Nb-0.045Ce合金的回复率达到96.9％。
热机械训练能有效提高合金形状回复率，特别是第一次训练提高最为显著。
Fe-Mn-Si基合金中加入适量的Cr，Ni，Nb等元素可以显著提高合金耐腐蚀性能，在碱性NaOH溶液中其耐蚀性是304，316不锈钢的3倍。
关键词：Fe-Mn-Si基合金，形状记忆效应，原位自生颗粒，预变形，时效温度，热机械训练，马氏体相变i原位自生碳化物颗粒增强Fe-Mn-Si基形状记忆合金及性能研究iiABSTRACTShape memory alloys are one kind of functional materials possessing a greatpractical use. The Fe-Mn-Si based alloys have a series of advantages such as low cost and processing easiness. However, the low shape memory recovery ratio and the limited anti-corrosion ability restrict their usage. In the present paper, the in-situ carbide particulate reinforced Fe-Mn-Si based shape memory alloys (SMA) were prepared by optimizing the compositions. The mechanical properties of the prepared alloys were also studied.Eight kinds of Fe-Mn-Si based SMA were designed by adding a suitable amountof Nb, V, Ti, and RE (Ce) elements. The Fe-Mn-Si based SMA reinforced with a uniformly dispersed in-situ carbide particulates were prepared.Optical microscope (OM), scanning electron microscope (SEM) and X-ray diffraction (XRD) were used to study the microstructures and phases of Fe-Mn-Si based alloys. The solid solution stated alloy matrix mainly consisted of the austenite and a small amount of heat reduced εmartensite. The presence of a suitable amountof heat reduced ε martensite favored the enhancement of the shape recovery ratio. With increasing the pre-deformation degree, the amount of the stress induced martensite increased, and its orientation changed from a single direction to a crossed from.Tensile tests were used to study the shape memory effect of the alloys by changing the processing parameters and the chemical compositions. It showed that the shape memory ratio of the solid solution stated alloys increased significantly after an ageing treatment (250 min) at a proper temperature (750℃) before deformation. The shape memory ratio of the alloys enhanced with increasing the ageing temperature. A maximum value was obtained at 750℃, above which the shape memory ratio showed a decrease. The shape recovery ratio of the prepared alloys decreased with increasing the pre-deformation degree. A best shape memory ratio was obtainable at 2% pre-deformation. The recovery ratio of Fe-14.0Mn-6.0Si-9.0Cr-5.0Ni-0.83Nb- 0.045Ce alloy reached a high value of 96.9%. The shape recovery ratio of the alloys could be effectively improved through suitable南京航空航天大学硕士学位论文thermo-mechanical training, especially the first cycle training.The anti-corrosion ability of the Fe-Mn-Si based alloys was improved by adding a suitable amount of Nb, V, Ti, and RE (Ce) elements. The experimental results showed that the anti-corrosion ability of alloys in NaOH solution was three times higher than that of 304 and 316 stainless steels.Key words: Fe-Mn-Si based alloy, Shape memory effect, In-situ autogeny particles, Pre-deformation, Aging temperature, Thermo-mechanical training, Martensite transformationiii原位自生碳化物颗粒增强Fe-Mn-Si基形状记忆合金及性能研究vi 图表清单图清单图1.1 普通金属与形状记忆合金的应力应变示意图 (1)图1.2 形状记忆合金晶体转变的示意图 (6)图1.3 半热弹性相变合金中形状记忆效应示意图 (8)图1.4 应力诱发马氏体相变示意图 (9)图1.5Fe-30Mn-6Si合金晶粒尺寸对形状记忆效应的影响 (12)图2.1 形状记忆效应关系图 (18)图2.2Si对Fe-30Mn-Si合金ε马氏体相变体积变化率的影响 (19)图2.3试样材料加工工序示意图 (21)图2.4 板材拉伸试样图 (21)图2.5试样拉伸示意图 (22)图2.6电解抛光示意图 (23)图3.1 时效温度对形状回复率的影响 (25)图3.2 不同合金试样的最佳时效温度变化 (26)图3.34#合金试样不同时效处理温度下750℃回复退火后的金相组织 (27)图3.44#合金试样750℃时效处理下高倍显微组织 (28)图3.5 图3.4中A点颗粒成分 (28)图3.6 不同成分合金在750℃时效处理时的金相组织 (30)图3.7 实验工序图 (31)图3.8 试样经750℃回复退火时预变形量对形状回复率的影响 (32)图3.9 预变形量对合金的影响 (33)图3.10 训练次数和回复率之间的关系 (36)图3.11 热机械训练后合金金相组织 (37)图3.124#合金试样X射线衍射图样 (39)图4.1 时效温度对合金硬度的影响 (42)图4.2时效温度对试样屈服强度的影响 (44)图4.3回弹高度测量示意图 (45)图4.4 不同载荷下时效温度对回弹性的影响 (49)承诺书本人郑重声明：所呈交的学位论文，是本人在导师指导下，独立进行研究工作所取得的成果。
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