锆合金变形机理及其板材织构演化规律

锆是核工业的重要结构材料,又是优秀的化工耐蚀结构材料。锆合金的织构会对它的屈服强度、蠕变和疲劳强度、应力腐蚀开裂行为以及辐照尺寸变化等产生很大影响,因此变形机理的研究和织构控制在锆合金的开发利用中有十分重要的地位。综述了锆合金的变形机理,介绍了锆合金板材在不同轧制温度下的织构演化规律,以及退火温度对锆合金板材织构的影响,并总结了织构对锆合金板材力学性能的影响。最后指出,目前对锆合金板材加工后的织构进行精确预测还十分困难,需进行详细深入的研究,同时在加工中产生的织构对加_丁过程的影响以及与温度、应力分布、合金成分和组织的关系还需进一步认识。     

锆合金变形机理及其板材织构演化规律

锆是核工业的重要结构材料,又是优秀的化工耐蚀结构材料.锆合金的织构会对它的屈服强度、蠕变和疲劳强度、应力腐蚀开裂行为以及辐照尺寸变化等产生很大影响,因此变形机理的研究和织构控制在锆合金的开发利用中有十分重要的地位.综述了锆合金的变形机理,介绍了锆合金板材在不同轧制温度下的织构演化规律,以及退火温度对锆合金板材织构的影响,并总结了织构对锆合金板材力学性能的影响.最后指出,目前对锆合金板材加工后的织构进行精确预测还十分困难,需进行详细深入的研究,同时在加工中产生的织构对加工过程的影响以及与温度、应力分布、合金成分和组织的关系还需进一步认识.     

连续退火对再加工锆合金腐蚀性能的影响

对在780℃下沿原板材横向热轧、冷轧及退火处理后的再加工锆合金进行金相织构、均匀腐蚀和疖状腐蚀测试和分析。结果表明:锆合金板材在再加工后及连续退火后,晶粒组织的粒度分布未发生明显变化,连续退火后的锆合金腐蚀性能未出现明显下降。     

连续退火对再加工锆合金腐蚀性能的影响

对在780℃下沿原板材横向热轧、冷轧及退火处理后的再加工锆合金进行金相织构、均匀腐蚀和疖状腐蚀测试和分析。结果表明:锆合金板材在再加工后及连续退火后,晶粒组织的粒度分布未发生明显变化,连续退火后的锆合金腐蚀性能未出现明显下降。     

织构对先进锆合金蠕变性能各向异性的影响

研究了两种组织形貌相似的先进锆合金M5TM和N36锆合金核燃料包壳管材的单轴拉伸和内压蠕变性能.利用x射线衍射仪分析了它们的织构.试验发现两种先进锆合金包壳材料的蠕变性能表现出明显的各向异性.根据试验条件下的蠕变机理,结合弹性粘塑性自洽模型定性地分析了织构对锆合金管材蠕变各向异性的影响,解释了先进锫合金各向异性随应力指数变化的共性规律.揭示了织构与先进锆合金管材蠕变各向异性的定性关系.由于成分和织构因素的共同作用,在研究的试验条件下,N36合金的初始蠕变应变、稳态蠕变速率低于M5合金.织构是合金蠕变行为产生各向异性的主要原因,对于再结晶状态的先进锆合金包壳管,具有(0002)织构特征时,应力指数越高(即施加的应力水平越高),其蠕变的各向异性值越大.     

TYM钼合金轧制工艺与组织结构及再结晶温度的关系

文中用X射线和金相技术研究了TYM钼合金板轧制工艺与组织结构及再结晶退火温度的关系。结果表明，多次交叉轧制态板材织构为聚集很强的{001}<110>，其组织纤维较粗，弥散相粒子分布不均匀，再结晶退火温度约在1300℃以下；一次交叉轧制态板材织构为{001}<110>，但聚集程度较低，同时存在极弱的{001}<100>立方织构，其组织纤维细、长，弥散相粒子分布均匀，再结晶退火温度可达1500℃以上。有关组织结构对合金高温性能的强化机制进行了详细分析。     

TiNiZr形状记忆合金的性能研究

系统地研究了锆对TiNiZr形状记忆合金性能的影响，对Ti49.4-xNi50.6Zrx(x=0,1,2,3)三元合金的相变温度进行了研究，表明合金相变温度随锆含量的增加先降后升；对合金系进行了机械性能及记忆性能研究，发现加锆后合金的机械性能和记忆性能都获得提高；此外还对Ti46.4Ni50.6Zr3的脆性根源进行了初步探讨。     

高强度织构对2524铝合金疲劳性能的影响

对分别含有高强度高斯织构和高强度立方织构状态的2种2524-T4铝合金板材的疲劳裂纹扩展速率和短裂纹扩展行为进行研究,用扫描电镜(SEM)观察疲劳试样断口形貌和疲劳短裂纹的扩展路径,研究织构类型对合金疲劳性能的影响。结果表明:高斯取向晶粒能够提高材料疲劳裂纹扩展的门槛值及增强疲劳裂纹的扩展抗力,使材料在更高的应力强度因子下发生失稳扩展;而高强度立方织构对疲劳性能的影响相对较小。在近门槛区,高斯晶粒通过裂纹偏转的形式有效阻碍短裂纹扩展,在稳态扩展区,高斯晶粒能明显降低疲劳裂纹的扩展速率,高斯织构还能延长合金疲劳裂纹稳态的扩展区,提高合金的疲劳损伤容限。因此,高强度高斯织构的2524-T4铝合金板材比立方织构的合金具有更好的疲劳性能。     

Zr-4合金板材微观组织异常条线现象的研究

采用金相显微镜、扫描电镜等检测手段对Zr-4合金板材微观组织中出现的异常条线现象进行研究,分析了Zr-4合金板材条线现象的本质、成因以及对其使用性能的影响。研究表明,Zr-4合金板材微观组织中出现的异常条线现象并不是裂纹、夹杂、氢化物、织构等缺陷的反映,而是由沿轧向成带状分布的粗大Zr(Fe,Cr)2第二相更容易遭受腐蚀造成的。此外,Zr-4合金板材微观组织中出现的条线现象对均匀腐蚀性能无明显影响,但带状分布的粗大第二相不利于板材的抗疖状腐蚀,并且会对板材的弯曲性能产生影响。     

异步轧制对Mg-Gd-Y-Zn-Zr板材组织、织构和性能的影响

以Mg-Gd-Y-Zn-Zr挤压态合金为材料，采用同步轧制（SR）和异步轧制（DSR）工艺，通过光学显微镜（OM）、电子背散射衍射（EBSD）、 X射线衍射（XRD）宏观织构检测以及室温拉伸等手段研究了两种轧制方式下板材微观组织的演变、织构组态及力学性能。结果表明：经SR和DSR轧制后，大尺寸的变形组织由于剪切破碎作用被细小的再结晶组织取代，两种轧板表层组织都比中心层组织更加细小均匀；与SR轧板相比，DSR轧板残留的变形区组织很少，动态再结晶程度更高，组织更加均匀；由EBSD分析结果可知，SR和DSR板材的再结晶机制均为连续动态再结晶；SR板材内部存在大量的低角度晶界（67.8%），仍然存在15μm以上的大晶粒，动态再结晶程度不高；DSR板材低角度晶界比例大大降低（25.8%），晶粒尺寸分布均匀，动态再结晶程度较高；SR板材呈现基底织构的特征，织构强度达到13.9; DSR板材基极向横向（TD）和轧向（RD）呈现均匀发散状态，织构强度降低到4.8；相同轧制条件下，DSR板材的抗拉强度和屈服强度分别比SR板材高30.1 MPa和38.2 MPa, DSR板材的延伸率（8.7%）比SR板材...     

SPD技术对锆及锆合金力学行为影响研究现状

综述了锆及锆合金剧烈塑性变形(SPD)后性能变化的研究进展,系统阐述了锆及锆合金经剧烈塑性变形后显微硬度、拉伸/压缩性能、高低周疲劳性能,重点介绍了SPD技术在纯锆、Zr-Nb系合金中的应用.经过剧烈塑性变形后,锆及锆合金的抗拉强度及屈服强度均显著提升,但依据剧烈塑性成形轨迹、合金成分、第二相分布、热处理制度不同,其提...     

Microstructural control of toughness in aluminium-lithium alloys

Investigation of the deformation behaviour of AlLi based alloys containing zirconium as a grain-refining addition shows that the poor toughness properties are attributed to the intense coplanar slip associated with δ' (Al₃Li) precipitation being unimpeded by the grain structure as a result of the pronounced deformation texture present in the sheet product; fracture proceeds via a transgranular shear failure mode which limits toughness. Changes in composition and thermomechanical treatment have been utilised in order to encourage the formation of additional precipitate phases, and, whilst δ' confers the major increment of strength to all AlLi based alloys, widespread precipitation of S phase (Al₂CuMg) within AlLiMgCuZr alloys is shown to influence strongly the deformation behaviour; in particular the propensity towards slip coplanarity is reduced, and significant improvements in toughness are obtained. Additionally, by promoting homogeneous deformation within the grain structure, the presence of S phase causes the material to display isotropic properties even though a strong texture remains in the zirconium-refined sheet product.     

Effects of Cerium on Texture and Mechanical Property of 2090 Aluminium-Lithium Alloys

Conventional processing of Al-Li alloys asstructural materials used in aerospace industries such as rolling, prestretching, solutioningand aging will produce various textures such asrolling texture, recrystallization texture whichcan lead to mechanical anisotropy. Adding Ceto Al-Li alloys by means of rare earth microalloying and purification, the mechanical properties will be improved[' ~3). It is significant tostudy the actions of Ce on Al-Li alloys from theviewpoint of texture, hilt resea…     

Delayed hydride cracking of zirconium alloys: Appearance conditions and basic laws

The data on and concepts of delayed hydride cracking (DHC) in zirconium alloys are generalized. DHC appearance conditions and the general laws of DHC are considered. The DHC parameters (threshold stress intensity factor K _1H, crack growth rate) are shown to depend on both external (temperature, irradiation, loading scheme) and internal (strength, texture, microstructure) factors.     

Hardening mechanism in melt-quenched Al-Zn-Mg-(Cu) alloys

The effect of various hardening factors on the mechanical properties of melt-quenched high-strength Al-Zn-Mg and Al-Zn-Mg-Cu alloys is considered. Alloys with zirconium and Group VIIIA metals are shown to have high mechanical properties. The high strength of these materials is achieved due to the precipitation of Al₃Zr (Ll₂) metastable phase particles and to a pronounced aging effect in materials alloyed with cobalt and nickel. High-strength melt-quenched 01949 (Al-Zn-Mg), 01959, and 01979 (Al-Zn-Mg-Cu) alloys containing zirconium, cobalt, and nickel are developed using these phenomena.     

Relationship between contractile strain ratioR and texture in zirconium alloy tubing

The crystallographic textures of zirconium alloy tubing used as cladding in nuclear reactor fuel are commonly characterized by the quantitative texture numbersF (Källström) and f_r (Kearns) which are derived from the direct and inverse pole figures. The texture numbers of zircaloy 2 and 4 tubes have been correlated experimentally with the value of the contractile strain ratioR which is a measure of the plastic anisotropy of the tube. The correlations were based on the results of 20 different tubing lots. Thef _r-R correlation shows much less data scatter than theF-R correlation. By assuming a simple plastic deformation model for zirconium alloys the following relations between texture and anisotropy are obtained:F=R- 1/R+1 and f_r = R/R+1 The theoretically derived relations are in good agreement with the experimental data. The procedure of correlating texture with plastic anisotropy is not limited to zirconium alloy tubing, but should be equally applicable to textured sheet and plate materials and other alloys with a limited number of slip systems.     

Methodological aspects of the quantitative texture analysis of HCP Alloy (Ti,Zr) sheet semiproducts

The specific features of the existing methods of quantitative texture analysis of semiproducts and products made of titanium and zirconium alloys are analyzed. A technique is proposed to determine the Kearns coefficients (f parameters) for sheets made of hcp-metal-based alloys with allowance for the weighting factor of each reflection in the standard stereographic triangle. The f parameters calculated for sheets made of a zirconium alloy and various titanium alloys using different techniques are compared. The accuracy of measuring the Kearns coefficients by the inverse pole figure method is estimated.     

Effect of Icosahedral Quasicrystalline Fraction and Extrusion Ratio on Microstructure, Mechanical Properties, and Anisotropy of Mg-Zn-Gd-Based Alloys

We have fabricated three types of Mg-Zn-Gd-based alloys containing the icosahedral quasicrystalline phase (I-phase) to investigate how volume fraction of the I-phase and extrusion ratio can have an impact on the microstructure, mechanical properties, and anisotropy of the as-extruded alloys. We find that grains are refined and that the ultimate tensile strength and elongation are improved as either the volume fraction of I-phase or the extrusion ratio is increased, which can be attributed to the secondary phase particle stimulate recrystallization nucleation and restrained grain boundary motion. Moreover, anisotropy is mitigated in all of the alloys as either the I-phase fraction or the extrusion ratio is increased owing to the coeffect of texture weakening and grain refinement as well as to the effect of I-phase on twinning. We also find that with the increase in the amount of the I-phase, the yield strength (YS) is decreased for the alloys extruded at a low ratio owing to the texture weakening, yet it is increased for the alloys extruded at high ratio owing to the strengthening originating from the I-phase and refined grains. The mechanical properties are improved for the alloys extruded at high ratio, which is due to their fine grains and uniform microstructure.