【作者】 李周龙；

【导师】 黎沃光；

【作者基本信息】 广东工业大学 ， 材料加工工程， 2008， 硕士

【摘要】 超弹性Cu-Al-Be形状记忆合金具有优良的超弹性性能,在商业应用中有着广阔的应用前景。本文对具有柱状晶组织的Cu-Al-Be形状记忆合金丝经过热变性后的性能作了系统的研究,以确定Cu-Al-Be形状记忆合金在工业化生产中实际应用的可能性。现在对Cu-Al-Be形状记忆合金的制备在国内还处于实验室研究阶段,对其热变形工艺的研究国内尚未见到。本课题对新型Cu-Al-Be合金的热变形能力进行了研究,并使用热型连铸法定向凝固以得到粗大的柱状晶组织,通过强化织构来提高Cu基合金的力学性能和疲劳性能。同时采用等温变形的方法使合金丝变形后的性能可以和铸态组织相媲美;同时对Cu-Al-Be合金在热变形状态下组织的变化和温度变化的关系作了系统的研究,分为大变形和小变形量两种状态加以总结;最后对于不同的变形量要求找出最为合理热变形工艺。采用水平式热型连铸装置在拉铸速度为350mm/min时制得Cu-Al-Be超弹性合金丝。热变形试验拟在400℃、450℃、500℃、550℃、600℃对Cu-Al-Be超弹性合金进行热变形试验,以测定Cu-Al-Be合金丝的抗拉强度和延伸率;用自制的弯曲疲劳试验机,测定了Cu-Al-Be合金的弯曲疲劳寿命;用X-射线衍射仪分析变形后Cu-Al-Be合金生成新相变化;并用金相显微镜观察合金在铸态、热处理后的组织形态;最后用扫描电镜观察不同温度下变形后合金丝的疲劳断口。研究结果表明:用热型连铸法拉铸的Cu-Al-Be合金可以获得柱状晶粒。在400℃和450℃变形后的试样保持了柱状晶结构和母相组织,机械性能较好。但是在此温度下,变形不仅比较困难,而且变形后的试样会出现了内裂纹,大大影响了变形后合金丝的机械性能,进行拉伸和弯曲时,裂纹从已产生的内裂纹处开始生长然后直至断裂。在500℃时,变形后的试样可以保持母相组织和柱状晶结构,且随着变形温度的升高,内裂纹已很少出现,且变形比较容易。在500℃变形后的试样具有优良的机械性能,延伸率可以达到40%,弯曲疲劳寿命较长,无论是进行大变形还是小变形均可以达到80000次以上,可以和铸态合金丝相媲美。在550℃和600℃变形,较500℃变形更为容易,可以做到一次锻打成型。但在此温度下进行后的试样组织已发生了变化,产生了新相γ₂,柱状晶结构也遭到破坏,所以在此温度下变形后的试样的机械性能最差,延伸率最大也不超过20%,弯曲疲劳寿命大大降低为30000次以下。更多还原

【Abstract】 Superelastic Cu-Al-Be SMA Wires with excellent properities of superelastic is very useful in the application of commerce.In this paper,the properties of a columnar crystal Cu-Al-Be shape memory alloy wire with thermal deformation have been studied to establiash the possibility of practical application in the industrialized production. However,in practical application,Cu-Al-Be shape memory alloy is difficult to ensure that,as long as the emergence of some small deformation,it will be disappear with super-elastic properties.Now the Cu-Al-Be shape memory alloys in the country is still in the laboratory research stage,its heat distortion of the domestic research has yet to see.The subject of a new Cu-Al-Be alloy thermal deformation capacity is studied and obtained a longitudinal columnar structure by heated mold continuous casting process,improving mechanical properties and super elasticity of this two alloy by strengthening texture.At the same time,the properities of alloy wires deformed by using methods such as temperature was comparables with organizations cast.The Cu-Al-Be in the thermal deformation state organizations and the changes in temperature changes the relationship between structure changes of Cu-Al-Be alloy wires in thermal deformation state was studied.Summing up by divided into small and large deformation.At last,the most reasonable thermal deformation process was found to different requirements.Cu-Al-Be SE alloy wires are cast by heated mold continuous casting process at 350mm/min casting speeds.The tensile strength and elongation rate of Cu-Al-Be alloy wire be measured by hest deformation at 400℃,450℃,500℃,550℃,600℃;The repeat bending fatigue life of Cu-Al-Be alloy wires is determined by a self-designed equipment;The phase changes of Cu-Al-Be alloy wires deformed were analyzed with X-ray Diffraction(XRD);Finally,the fatigue fracture of deformed alloy wire be observed at different temperatures by scanning electron microscopy.The result shows that:the Cu-Al-Be alloy wires cast by heated mold continuous casting process can get columnar grain structure.The cylindrical grain structure and mother phase be maintained in deforming at 400℃and 450℃,better mechanical properties.However,not only deformation be more difficult,but also the crack will be appear in the specimen after the deformation at this temperature,the properties of deformed alloy wire be affected greatly.The cracks have been generated from within the cracks and then until the beginning of growth Fault when be drawing and bending. In 500℃,The mother phase and columnar crystal structure of the specimen defomed can be maintained,and with the increase of deformation temperature,cracks have been rare,and more easily deformed.In 500℃,the sample deformed has excellent mechanical properties,the elongation rate up to 40%,bending fatigue life longer, whether it is a large deformation or small deformation can reach more than 80,000 times,with comprarable with casting alloy wire.The deformation at 550℃and 600℃be more easy at 500℃,forging needs one times.However,the sample organization has changed,generating a new phase,cylindrical grain organizations were also damaged at this temperature,so at this temperature,the mechanical properties of the sample deformed be worst,the elongation rate not up to 20 percent,Bending greatly reduce fatigue life of 30,000 times.更多还原