Influence of Texture on Mechanical Behavior of Friction-Stir-Processed Magnesium Alloy

Friction stir processing (FSP) improves the mechanical properties of metallic materials. In this study, a magnesium alloy AZ31B was friction stir processed by using single and multiple pass. The friction-stir-processed magnesium alloy exhibits higher tensile strength and ductility in the transverse direction (TD) compared to the longitudinal direction (LD). Both single pass and multiple (two) pass friction-stir-processed material show similar anisotropy in tensile properties, but the multiple pass friction-stir-processed material shows fine-grained microstructure with higher tensile strength and ductility. The tensile anisotropy in the friction-stir-processed AZ31B originated from the textured microstructure that evolved during FSP.     

Effect of Ratcheting on Tensile Behavior of Zircaloy-2 at Room Temperature

Asymmetric cyclic loading, known as ratcheting fatigue, causes accumulation of cyclic plastic strain and reduces fatigue life of components. This investigation was undertaken to examine the effect of pre-ratcheting on tensile properties of the Zircaloy-2. Stress controlled fatigue tests were performed at room temperature (RT) for 200 cycles with different combinations of the parameters: mean stress (σ_m), stress amplitude (σ_a) and stress rate (\(\dot{\sigma }\)). Tensile properties of these samples were evaluated at room temperature. There was marked increase in the yield strength but there was far less effect on the tensile strength. The ductility was reduced due to prior ratcheting. The results have been discussed in terms of work hardening under different combinations of the ratcheting parameters.     

Texture and stress state dependent creep in Zircaloy-2

An experimental program was conducted to characterize creep strength differential (CSD) effects in Zircaloy-2 by the determination of differences in the magnitude of creep deformation in specimens under uniaxial tension and compression. The texture dependence of creep in these specimens was also characterized. Uniaxial thermal creep tests were conducted in tension and compression at 325 to 400 °C and 69 to 172 MPa on specimens taken from the three principal directions of textured Zircaloy-2 plate fabricated in both the recrystallized and the cold-worked, stress relieved condition. Stress relaxation tests were conducted at 400 °C on similar specimens to substantiate results of the thermal creep tests. Creep strength-differential effects were found in all three principal directions of both types of plate, and it appeared that the CSD was larger in the longitudinal than the normal direction. Creep strains in tension were as much as three times larger than those in compression. In addition, the relative magnitude of creep strains indicated that the tensile creep strength at 400 °C was proportional to the resolved fraction of basal poles in the test direction. Cold work attenuated this anisotropy, and “transitions’in some creep tests on recrystallized material reversed this anisotropy. Finally, the thermal creep data were used to construct creep loci which graphically illustrate these characteristics.     

Effect of Brazing on the Mechanical Anisotropy of Zircaloy-4 Nuclear Fuel Cladding

Abstract

The anisotropy of mechanical properties as measured by Knoop microhardness in Zircaloy-4 nuclear fuel cladding containing a range of oxygen and nitrogen impurity contents is related to the heat treatment schedule experienced in simulated brazing treatments. With increasing (0 + N) contents there was an increase in the overall Knoop hardness value but no significant effects on the degree of mechanical anisotropy. The effect of the brazing cycle (short times at temperatures ≥1050°C) is to lower the overall micro hardness value and to reduce the degree of anisotropy. However, no simulated brazing cycle entirely eliminated the anisotropy and the general orientations of the “hard” and “soft” directions remained the same. An annealing treatment of 1h at 850°C produced the highest degree of mechanical isotropy.

Résumé

L'anisotropie des propriétés mécaniques d'un cladding de Zircalloy-4 destiné à combustible nucléaire contenant diverses teneurs d'oxygène et d'azote a été mesurée par microdureté Knoop et a été reliée à des cycles thermiques simulés de brasage. Des teneurs croissantes d'impuretés (O + N) font augmenter la microdureté sans avoir d'effet sur le degré d'anisotropie. Le cycle de bras age (court séjour à T ≥ 1050°C) a pour sa part comme effet de diminuer la microdureté et de réduire le degré d'anisotropie. Cependant, aucun cycle de brasage simulé n'élimine entièrement l'anisotropie et l'orientation générale des directions principales d'anisotropie (directions des dureté minimales et maximales) demeurent les mêmes. Un recuit d'une heure à 850°C produit le plus haut degré d'isotropie mécanique.     

Microstructure,Texture, and Mechanical Behavior of As-cast Ni-Fe-W Matrix Alloy

This article describes the tensile properties, flow, and work-hardening behavior of an experimental alloy 53Ni-29Fe-18W in as-cast condition. The microstructure of the alloy 53Ni-29Fe-18W displays single phase (fcc) in as-cast condition along with typical dendritic features. The bulk texture of the as-cast alloy reveals the triclinic sample symmetry and characteristic nature of coarse-grained materials. The alloy exhibits maximum strength (σ_YS and σ_UTS) values along the transverse direction. The elongation values are maximum and minimum along the transverse and longitudinal directions, respectively. Tensile fracture surfaces of both the longitudinal and transverse samples display complete ductile fracture features. Two types of slip lines, namely, planar and intersecting, are observed in deformed specimens and the density of slip lines increases with increasing the amount of deformation. The alloy displays moderate in-plane anisotropy (A_IP) and reasonably low anisotropic index (δ) values, respectively. The instantaneous or work-hardening rate curves portray three typical stages (I through III) along both the longitudinal and transverse directions. The alloy exhibits dislocation-controlled strain hardening during tensile testing, and slip is the predominant deformation mechanism.     

Controlling Mechanical Behavior of TWIP Steels by Tuning Texture and Stacking Faults

Metallurgical and Materials Transactions A - We developed an Fe–22Mn–0.6C–1.5Al TWIP steel and investigated how thermo-mechanical processes affect the mechanical properties. In...     

Effect of Solidification Texture on the Magnetostrictive Behavior of Galfenol

This study investigates the magnetostrictive functionality of crystallographic textures developed by directional solidification of a vacuum-melted galfenol cast button. A polycrystalline Fe_82.4Ga_17.6 alloy was melted using vacuum arc melting and solidified in a water-cooled copper mold. Optical metallography confirmed the development of large columnar grains in the solidification microstructure. Phase constitution and magnetic domain structures of sample were studied by X-ray diffraction (XRD) and magnetic force microscopy (MFM). The results showed that the cast button has a disordered body-centered cubic (bcc) (A2) single-phase structure that consisted of a combination of well-aligned stripe-like and maze-like magnetic domains. To investigate the magnetostriction behavior, a couple of pins were cut along columnar grains as well as in the transverse direction. Magnetostriction was measured in the presence of an externally applied magnetic field. It was found that pins cut along the columnar grains comprised very high magnetostriction, whereas transverse pins had lower magnetostriction against the applied field.     

Effect of Lanthanum on Mechanical Properties of ZL702 Alloy at Room and High Temperature Condition

Effect of Lanthanum on Mechanical Properties of ZL702 Alloy at Room and High Temperature Condition     

TC4钛合金轧板的织构对动态力学性能影响

利用分离式Hopkinson压杆试验装置,对具有不同织构特征的TC4合金试样进行动态压缩试验,分析织构特征对钛合金轧板各方向动态力学性能的影响。结果表明,900℃轧制板材的主织构为{1219}<12391>±30°RD,织构强度为10.557,在φ1=15°时出现峰值,有一定的织构分散,其中晶面{1219}平行板材的轧面,与基面{0001}夹角26.6°,晶向由〈1010〉向〈6 331〉方向漫散;950℃轧板的主织构为{1219}〈5321〉±20°RD,织构类型与900℃轧板相似,但织构强度为6.387,相对900℃轧板较弱,晶向由〈7341〉向〈4311〉方向漫散,在φ1=35°出现峰值;1050℃轧制板材的主织构为{12 19}〈1010〉,织构比较集中,织构强度为15.333,晶向〈101-0〉平行板材的轧向,与c轴为90°夹角。950℃轧制的TC4板材,织构强度较弱,其轧向(RD)、横向(TD)、法向(ND)的动态流变应力和动态均匀塑性应变差别不明显。900℃和1050℃轧制的TC4板材,由于织构强度较高,轧板存在明显的各向异性:TD方向的动态流变应力最高,ND次之,RD最低;RD方向的动态均匀塑性应变最大,ND次之,TD最小。     

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.     

Deformation Behavior of Duplex Zircaloy-4-Oxygen Alloys

The mechanical properties of two-phase Zircaloy-4-oxygen alloys at thermal equilibrium have been determined. The strength of these alloys depends to a large extent on their microstructure. The strengthening behavior for alloys having isolateda grains in the softer β matrix is similar to the dispersed particle strengthening. The yield strength of these alloys is found to obey the Petch relationship, (MPa), whereλ _β is the mean free path of β phase inμm. As the volume fraction ofa phase increases, its aspect ratio also increases. This allows more effective load transfer from the matrix to the hardera phase. It has been shown that the strength of these alloys obeys a modified rule of mixtures. The alloys having equiaxeda grains in the β matrix show large strain rate sensitivities at low strain rate. The deformation behavior is interpreted in terms of dislocation slip in the β matrix and diffusion assisted climb near the interphase boundary.     

The Effect of Twins on the Mechanical Behavior of Boron Carbide

The microstructure and mechanical properties of boron carbide (B₄C) samples processed by slip casting were compared with those processed by the conventional hot-pressing technique. Although the quasi-static and dynamic mechanical experiments showed comparable results between the slip-cast and hot-pressed B₄C, scanning electron microscopy and electron backscattered diffraction of the B₄C samples revealed significant differences in the microstructure. A notable difference was the numerous growth twins in the slip-cast samples. The twin planes were determined to be { 10[`1] 1 } left{ { 10bar{1} 1} right} and consisted of 35 pct of the boundary population in the slip-cast B₄C but only 1 pct of the boundary population in the hot-pressed B₄C. It was hypothesized that the presence of twins will cause a different failure mechanism. The effect of the twins on the stress state was examined by finite-element simulations and will also be discussed.     

Effect of Annealing on the Microstructure,Texture and Mechanical Properties of a Dual-Phase Ultrahigh-strength TWIP Steel

Metallurgical and Materials Transactions A - The present study investigates the effect of annealing time and temperature on the microstructural restoration (by recovery and recrystallization),...     

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…     

Effect of Multi-Axial Loading on Residual Strain Tensor for 12L14 Steel Alloy

Evaluating the state of residual strain or stress is critically important for structural materials and for reliable design of complex shape components that need to function in extreme environment subjected to large thermo-mechanical loading. When residual stress state is superposed to external loads, it can lead to reduction or increase in failure strength. Past diffraction studies for evaluating the residual strain state involved measuring lattice spacings in three orthogonal directions and do not often correspond to principal directions. To completely resolve the state of strain at a given location, a full strain tensor must be determined. This is especially important when characterizing materials or metallic components exposed to biaxial or complex loading. Neutron diffraction at the second Generation Neutron Residual Stress Facility (NRSF2) at Oak Ridge National Laboratory is used in this study to measure strain tensors associated with different modes of stress path. Hollow cylinder steel samples with 2 mm wall thickness are subjected to either pure axial extension or pure torsion to simulate multi-axial loading conditions. A virgin sample that is not subjected to any deformation, but subjected to identical manufacturing conditions and machining steps involved to obtain hollow cylinder geometry is used for obtaining reference d-spacing for given hkl planes at target spatial location(s). The two samples which are subjected to either pure tension or torsion are loaded to a deformation state that corresponded to equal amount of octahedral shear strain which is an invariant. This procedure is used so that a basis for comparison between the two samples can be made to isolate the stress path effects. A 2-circle Huber orienteer is used to obtain strain measurements on identical gauge volume at a series of φ and ψ values. The residual state of stress tensor corresponding to ex situ (upon unloading) conditions is presented for three lattice planes (211, 110, 200) for a bcc ferritic system exposed to tension and pure torsion.     

晶粒细化对Zr-4合金均匀腐蚀性能的影响

通过超声喷丸处理在Zr-4合金表面获得细晶组织,400 ℃高压釜实验表明其耐蚀性能优于原始组织.采用场发射扫描电镜和X射线衍射,观察并计算了细晶组织的晶粒形貌与尺寸分布.采用金相显微镜、原子力显微镜和X射线衍射,分析了不同腐蚀时间的氧化膜形貌和结构的演变.结果表明,喷丸处理在细化晶粒的同时会增加样品表面微观缺陷,从而促进保护性氧化膜的形成,提高Zr-4均匀的耐腐蚀性能.     

Steel Microstructure Effect on Mechanical Properties and Corrosion Behavior of High Strength Low Carbon Steel

Different thermomechanical treatments were applied to a high strength low carbon steel with a novel chemical composition. As a result, three different microstructures were produced with dissimilar mechanical and corrosion properties. Subsequently, a tempering heat treatment was applied to redistribute the phases in the steel. Microstructure A with 56 pct martensite and 32 pct bainite presented high strength but medium ductility; microstructure C with 95 pct ferrite and 3 pct martensite/austenite resulted in low strength and high ductility, and finally microstructure B with 98 pct bainite and 2 pct martensite/austenite resulted in high strength and ductility. Alternatively the corrosion behavior obtained by polarization curves was characterized in 0.1 M H₂SO₄, 3 M H₂SO₄, 3.5 wt pct NaCl, and NS4 solutions resulting in similar magnitudes, while the corrosion behavior acquired by electrochemical impedance spectroscopy had slightly differences in 3 M H₂SO₄.     

加工方法对钽板力学性能以及织构的影响

研究了加工方法对钽板力学性能的影响，通过金相显微镜观察了钽板的微观组织，并通过X射线测定了不同状态下钽板的织构。结果表明：一次交叉轧制可以更有效地减小钽板力学性能的各向异性和获得细晶粒，并且可以获得强烈的{111}〈uvw〉织构。通过研究，最终确定了生产钽电解电容器外壳用钽板的生产工艺。     

Effect of Microfabric on Mechanical Behavior of Kaolin Clay Using Cubical True Triaxial Testing

Various aspects of the mechanical behavior of kaolin clay are discussed in light of experimental observations from a series of strain controlled true triaxial undrained tests performed on cubical kaolin clay specimens with flocculated and dispersed microfabric, using a fully automated flexible boundary experimental setup with real-time feedback control system. The laboratory procedures used to prepare flocculated and dispersed microfabric specimens are presented. Mercury intrusion porosimetry is used to evaluate the pore structure of these specimens. The influence of microfabric on the consolidation behavior of kaolin clay is evaluated based on the data obtained from K0 consolidation during constant rate of strain tests and the isotropic consolidation during true triaxial tests. Undrained tests on kaolin clay show that the following vary with microfabric of specimen: The shear stiffness, excess pore pressure generated during shear, and strength and strain to failure. For both microfabrics, the observed strength behavior using cubical triaxial testing shows a similar pattern of variation with applied stress anisotropy; hence, only a marginal influence of fabric-induced anisotropy.     

Effect of Thermomechanical Processing on Microstructure,Texture Evolution,and Mechanical Properties of Al-Mg-Si-Cu Alloys with Different Zn Contents

The effect of thermomechanical processing on microstructure, texture evolution, and mechanical properties of Al-Mg-Si-Cu alloys with different Zn contents was studied by mechanical properties, microstructure, and texture characterization in the present study. The results show that thermomechanical processing has a significant influence on the evolution of microstructure and texture and on the final mechanical properties, independently of Zn contents. Compared with the T4P-treated (first preaged at 353 K (80 °C) for 12 hours and then naturally aged for 14 days) sheets with high final cold rolling reduction, the T4P-treated sheets with low final cold rolling reduction possess almost identical strength and elongation and higher average r values. Compared with the intermediate annealed sheets with high final cold rolling reduction, the intermediate annealed sheets with low final cold rolling reduction contain a higher number of particles with a smaller size. After solution treatment, in contrast to the sheets with high final cold rolling reduction, the sheets with low final cold rolling reduction possess finer grain structure and tend to form a weaker recrystallization texture. The recrystallization texture may be affected by particle distribution, grain size, and final cold rolling texture. Finally, the visco-plastic self-consistent (VPSC) model was used to predict r values.