【作者】 邱日盛；

【导师】 栾佰峰；

【作者基本信息】 重庆大学 ， 材料科学与工程， 2014， 博士

【摘要】 本论文以8种不同成分的锆合金(N1、N2、N3、N4、N5、N18、T1和T7)为主要研究对象，采用电子背散射衍射(EBSD)、电子通道衬度像(ECC)、透射电子显微镜(TEM)、定量金相、差示扫描量热法(DSC)等分析技术，系统定量的研究了锆合金板材及管材加工过程中显微组织演变规律，合金成分(Cu、Cr和Sn元素)对锆合金中第二相及相变行为的影响，初步探讨了第二相析出动力学机制。主要研究结论如下：(1) T1和T7锆合金板材及管材在冷轧过程中形成了c轴平行于法向的难变形晶粒，第二相随着冷轧变形量的增大分布由流线型逐渐向弥散型转变，且轧制变形对第二相平均尺寸没有明显影响。在冷轧后的退火过程中，第二相发生Ostwald熟化，此过程符合Kahlweit的二阶长大动力学，而晶粒长大过程符合齐纳钉扎模型。(2) T1管材含有尺寸较小的BCC结构的βNb和尺寸较大的HCP结构的Zr-Nb-Fe第二相。处于晶界处的第二相多为Zr-Nb-Fe相，且部分Zr-Nb-Fe相中含有层错结构。在加工过程中T1管材中的第二相由流线型逐渐分解，形成包含有两个或多个βNb和Zr-Nb-Fe粒子的团簇，最终形成弥散分布。(3) N1、N3、N4、N5和N18合金系中均含有细小的HCP或FCC结构的Zr(Fe,Cr, Nb)2Laves相，且Laves相中存在层错结构。在锆合金中添加Cu、Cr和Sn元素后，添加元素对合金中的第二相产生影响。Cu元素的添加主导了Zr2Fe和Zr3Fe颗粒的形成，减小了第二相平均尺寸。Cr元素促进小的Laves相的形成，抑制Zr2Fe和Zr3Fe大颗粒的析出，显著减小第二相平均尺寸。Sn元素含量变化对合金中第二相种类没有影响，但随着元素含量的降低，第二相有明显减小趋势。(4)采用DSC、淬火实验及热力学外推模型对N1-N5和N18合金的α→β相变温度进行测定。对比实验数据及模型计算结果得出，淬火实验所得Tα→α+β最接近相变平衡区域的温度。DSC所测相变温度点整体高于淬火实验结果，为非平衡状态的温度点，但整体偏离幅度较小，可作为α→β相变温度的参考依据。Zhu和Devletian的热力学模型及方法计算的Tα→α+β与淬火数据相吻合，证明此模型可以较好的应用于锆合金的Tα→α+β外推计算。(5)合金元素在升温和降温过程中对α→β和β→α相变温度有较大影响。在升温过程中，Cu元素的添加使Tα→α+β降低，Tα+β→β升高，扩大了β相区；Cr元素的添加使Tα→α+β降低，Tα+β→β升高，扩大了β相区；Sn元素含量的升高导致Tα→α+β升高，Tα+β→β降低，扩大了α相区。在降温过程中，Cu元素使Tβ→α+β和Tα+β→α均升高，但Tα+β→α升高幅度更大，扩大了β相区；Cr元素使Tβ→α+β升高，针对不同合金对其Tα+β→α影响有所差异，但总体上扩大β相区；Sn元素含量的增加会使得Tβ→α+β降低，Tα+β→α升高，扩大了α相区。综上可知：Cu元素和Cr元素是β相稳定元素，Sn元素是α相稳定元素。(6)6种合金在不同升温速率下β相体积分数与温度呈S型曲线关系。不同合金第二相析出活化能与析出温度之间的关系曲线变化趋势相似，析出初期活化能较大，在10%-90%析出量范围内，活化能变化较小，临近结束时，活化能继续下降。更多还原

【Abstract】 The thesis studied several kinds of Zirconium alloys with different componentswhich were N1, N2, N3, N4, N5, N18, T1and T7alloys by SEM-SE, SEM-ECC,EBSD, TEM and DSC. The microstructural evolution of Zr alloy sheets and tubesduring processes and the effects of alloy elements (Cu, Cr and Sn) on the second phasesand phases transformation of Zr alloys were researched. At the same time, the dynamicmechanism of second phases precipitation were discussed simply. Some conclusionswere obtained below:(1) The undeformed microstructure of T1and T7Zr alloy sheets and tubes withc//ND (normal direction) was formed during cooled rolling. The distribution of secondphases was transformed from streamline distribution to diffusion distribution duringcooled rolling and the changes of second phases sizes cannot be observed obviously.The process of second phase growth fits for the Ostwald during annealing after cooledrolling, which is in good agreement with the curve calculated for second order kinetics.(2) T1tube contains βNbwith BCC structure and small size and Zr-Nb-Fe withFCC and bigger sizes. Most of second particles distributed in grain boundaries areZr-Nb-Fe phase which have stacking faults. The second particles of T1tube decomposeduring process and formed cluster contained two or more second particles.(3) Zr(Fe, Cr, Nb)2Laves with HCP or FCC and tiny sizes were observed in N1,N3, N4, N5and N18alloys and stacking faults were found in these Laves phases. TheCu, Cr and Sn elements have significant effects on the second phases of Zr alloys. theZr2Fe and Zr3Fe were formed by adding Cu and the formation of Laves phases werepromoted by adding Cr. The types of second phases were not changed by adding Sn.Meanwhile, the alloys elements have important effects on the second particle sizes.(4) The α→β transformed temperatures were measured by DSC, quenching andcalculated used equilibrium phase transformation model built by Zhu and Devletian.Compared the measuring dates and calculative results, the result measured byquenching is more agree with the temperature of equilibrium phase transformation. Thedate measured by DSC is slightly higher than that of quenching, which can refer toactual temperature of α→β phase transformation. The equilibrium phase transformationmodel by Zhu and Devletian were used to calculate the temperature of phasetransformation of Zr alloys. The calculative results were accorded with the date of quenching, proving that the model can be used in calculation of phase transformationtemperature of Zr alloys successfully.(5) Alloy elements have significant effects on the temperatures of α→β和β→αtransformations. During the heating process, the Tα→α+βdecreases and Tα+β→βincreaseswith Cu of Cr addition, which increase the region of the β phase. The Tα→α+βincreasesand Tα+β→βdecreases with the increase of content of Sn, which increase the region of αphase. During the cooling process, the Tβ→α+βand Tα+β→αare increased by Cu addition,while Tα+β→αincrease more than that of Tβ→α+β, which increase the region of β. TheTβ→α+βincreases by Cr addition, while Tα+β→αis affected differently for different alloysby Cr element. However, the region of β is enlarged. The Tβ→α+βand Tα+β→αaredecreased and increase respectively, which enlarge the region of α. Above all, the Cuand Cr elements can steady the region of β and Sn can steady the region of α.(6) The ship of volume fraction of β phase and temperature relational grahp is ‘S’.The relationship of energy (E) and precipitation temperature is similar in differentalloys that the E is highest in starting precipitation temperature and the change of E isnot apparent when the precipitation contents is about10%-90%, while the E is decreasenear the finishing precipitation temperature.更多还原