Sputtering targets made of an Si-Ti-Co alloy

The effect of the cooling rate on the microstructure and the micromechanical properties of a resistance air-cast Si-23% Ti-10% Co alloy and on the residual stresses in magnetron sputtering targets made of it is studied. The choice of a proper temperature schedule of melting the alloy and the optimum cooling rate of the alloy melt are shown to result in a homogeneous fine-grained structure of the alloy, high strength characteristics of the targets, and a low level of residual thermal stresses in them.     

Magnetron sputtering targets made of a resistance alloy

The effect of the cooling rate on the microstructure and residual stresses of targets made of an Si-37% Cr-10% Ni resistance alloy has been studied. It is found that, at cooling rates below 30 K/s, the residual stresses in the targets made of this alloy are minimal. High-quality targets are shown to be produced from the Si-37% Cr-10% Ni resistance alloy by casting in air.     

Sputtering Si-Co alloy targets

The effect of the cooling rate on the microstructure, micromechanical characteristics, and residual thermal stresses of targets from a Si-30% Co alloy is studied. The required quality of the targets from this alloy can be obtained at a cooling rate in the range 5–50°C/s. The alloy structure is homogeneous and fine-grained and is characterized by high strength properties. The level of residual stresses in the target is minimal, and their distribution is uniform.     

Resistance Si–Ti–Ce alloy for sputtering targets

The effect of the cooling rate of an Si–20% Ti–5% Ce alloy on the microstructure, the micromechanical characteristics, and the residual thermal stresses in targets prepared from the alloy is studied. The required amount of targets prepared from this alloy can be obtained when it is cooled at a rate from 20 to 70°C/s. In this case, the alloy has a homogeneous structure and exhibits high strength characteristics; the residual stresses in a target are minimal and their distribution is the most uniform.     

Si-Ni-Fe alloys for magnetron sputtering targets

The effect of the cooling rate on the microstructure, micromechanical properties, and thermal residual stresses of magnetron sputtering targets made of cast resistance alloys Si-10% Ni-4% Fe and Si-15% Ni-6% Fe is studied. The optimum cooling rates of castings that provide a homogeneous fine-grained structure, high strength characteristics, and the minimum level of residual stresses in the targets are found.     

沸水淬火对铝合金锻件组织与机械性能的影响

铝合金锻件在冷水中淬火时由于冷却速度快，残余应力集中，机械加工成　成品后应力释放，往往发生不良　　　　变　形，造成零件尺寸超差。作者研究分析了铝合金锻件在沸水中淬火后的残余应力、机械性能、抗腐蚀性及金相组织，认为在生产条件下铝合金锻件沸水淬火在技术上是合理的，可以明显减少残余应力。     

Experience of Application of EBW in Producing Welded VT41 Alloy Drums in the Design of an HPC in an Advanced Engine

The conditions of electron-beam welding (EBW) of ring samples made of a VT41 alloy are adjusted to produce large welded joints of this alloy for a high-pressure compressor (HPC) of an advanced engine. The problems of quality control of a welded joint, the level of residual stresses in the near-weld zone, the microstructure of the welded joint, and its properties are considered.     

As-Cast Residual Stresses in an Aluminum Alloy AA6063 Billet: Neutron Diffraction Measurements and Finite Element Modeling

The presence of thermally induced residual stresses, created during the industrial direct chill (DC) casting process of aluminum alloys, can cause both significant safety concerns and the formation of defects during downstream processing. Although numerical models have been previously developed to compute these residual stresses, most of the computations have been validated only against measured surface distortions. Recently, the variation in residual elastic strains in the steady-state regime of casting has been measured as a function of radial position using neutron diffraction (ND) in an AA6063 grain-refined cylindrical billet. In the present study, these measurements are used to show that a well-designed thermomechanical finite element (FE) process model can reproduce relatively well the experimental results. A sensitivity analysis is then carried out to determine the relative effect of the various mechanical parameters when computing the as-cast residual stresses in a cylindrical billet. Two model parameters have been investigated: the temperature when the alloy starts to thermally contract and the plasticity behavior. It is shown that the mechanical properties at low temperatures have a much larger influence on the residual stresses than those at high temperatures.     

A Comparison of Residual Stress Development in Inertia Friction Welded Fine Grain and Coarse Grain Nickel-Base Superalloy

The effect of the base material microstructure on the development of residual stresses across the weld line in inertia friction welds (IFWs) of high-strength nickel-base superalloy RR1000 was studied using neutron diffraction. A comparison was carried out between tubular IFW specimens generated from RR1000 heat treated below (fine grain (FG) structure) and above (coarse grain (CG) structure) the γ′-solvus. Residual stresses were mapped in the as-welded (AW) condition and, after a postweld heat treatment (PWHT), optimized for maximum alloy strength. The highest tensile stresses were generally found in the hoop direction at the weld line near the inner diameter of the tubular-shaped specimens. A comparison between the residual stresses generated in FG and CG RR1000 suggests that the starting microstructure has little influence on the maximum residual stresses generated in the weld even though different levels of energy must be input to achieve a successful weld in each case. The residual stresses in the postweld heat treated samples were about 35 pct less than for the AW condition. Despite the fact that the high-temperature properties of the two parent microstructures are different, no significant differences in terms of stress relief were found between the FG and CG RR1000 IFWs. Since the actual weld microstructures of FG and CG RR1000 inertia welds are very similar, the results suggest that it is the weld microstructure and its associated high-temperature properties rather than the parent material that affects the overall weld stress distribution and its subsequent stress relief.     

深冷处理消除铝合金残余应力的研究

本文介绍了铝合金消除残余应力的深冷处理技术,分析了深冷处理过程的应力状态,给出了残余应力消除的机理是应力反转、晶粒细化和原子间的动能转移。     

The contribution of machine-induced residual stress to the pitting susceptibility of an Iron-1 Wt Pct nickel binary alloy

The pitting susceptibility of a variously machined binary iron-1 wt pct nickel alloy in 5 M sodium hydroxide solution at 373 K has been measured and correlated with the surface residual macrostress introduced by the machining process. Stresses were measured using the X-ray diffractometer technique. Tensile surface residual macrostresses increase the corrosion pitting susceptibility whereas compressive stresses decrease susceptibility.     

The influence of the nanosized reinforcing phase on the behavioral features of the 1953T1 aluminum alloy under cyclic load

The results of an investigation into the interrelation between the fatigue behavior (number N of cycles to failure) and the level of surface residual stresses (σ) of the cyclic deformation of the samples of high-tensile aluminum alloy with the nanosized reinforcing phase, which is used for the production of drill pipes, are presented. The tests were performed at the zero-to-tension stress cycle with a maximum tensile load of 160 MPa. To determine the level of σ, a DRP-RIKOR X-ray diffractometer was used. As a result, a substantial increase in fatigue strength (an increase in the number of cycles to failure) is found in the presence of the starting compressional surface residual stresses of about −120...−200 MPa (0.25–0.4 of the yield strength of the alloy). The dependence σ(N) has a nonmonotonic character that can be attributed to the nonuniformity of the local plastic deformation near the dispersed intermetallic inclusions. However, the indicated dependence with the locally cyclic character tends to an increase, which is expressed by a linear function, allowing us to evaluate and forecast the failure according to the level of the surface residual stresses.     

X-ray technique for the estimation of residual stresses after shot-blasting metal forming

A technique is developed for the correction of the depth distribution of residual stresses measured by an X-ray method with allowance for their relaxation upon the removal of surface layers. This technique is applied to the study of a D16 aluminum alloy strip subjected to shot-blasting metal forming. This technique can be used to estimate the distribution of residual stresses across massive parts after various types of treatment.     

Neutron diffraction and finite element analysis of quenching residual stress of GH4169 super alloy

The quenching process is indispensable for manufacturing the superalloys. However, high residual stress is inevitably induced by the large heat gradient, which influences the mechanical properties of the alloys. Therefore, it is of great significance to accurately characterize the internal residual stress of the super alloy and establish an effective finite element modeling. The quench- induced residual stresses of GH4169 super alloy were measured using neutron diffraction stress instrument. The results show that the center of the workpiece is subjected to tensile stress in three directions (hoop, radial and axial), which is about 400MPa. The rims of workpiece are subjected to compressive stress in one or two directions (hoop or axial), which is from -300MPa to -400MPa. The temperature and strain/stress fields of the GH4169 super alloy workpiece during quenching process were simulated by a 3D finite element model. The calculated residual strain/stress at the center and rim of the workpiece are compared to those by neutron diffraction, which shows good correspondence. These data provide reliable evidences to the formation of the residual stress during quenching.     

Determination of Bulk Residual Stresses in Electron Beam Additive-Manufactured Aluminum

Additive-manufactured aluminum alloy deposits were analyzed using neutron diffraction to characterize the effect of intermediate stress relief anneal heat treatment on bulk residual stresses in the final part. Based on measured interplanar spacing, stresses were calculated at various locations along a single bead, stacked wall deposit. A comparison between an uninterrupted deposited wall and an interrupted, stress-relieved, and annealed deposited wall showed a measureable reduction in residual stress magnitude at the interface with a corresponding shift in stress character into the deposit. This shift changes the interface stresses from purely compressive to partially tensile. The residual stress profile varied along the length of the deposit, and the heat-treatment procedure reduced the overall magnitude of the stress at the interface by 10 through 25 MPa. These results are interpreted in terms of thermal gradients inherent to the process and compared with prior residual stress-characterization studies in additive-manufactured metallic structures.     

Phase Composition,Texture, and Residual Stresses in Al–Cu–Li Friction Stir Welds

The formation of the phase composition, the texture, and the residual stresses in the V-1469 alloy joint (Al–Cu–Li system) fabricated by friction stir welding is studied. A numerical correlation between the phase composition, the hardness, and the residual stresses in various zones and sections of the welded joint is found     

Modeling of anisotropic behavior of weakly bonded fiber reinforced MMC's

The anisotropic mechanical behavior of a continuous fiber reinforced Ti alloy matrix composite which possesses a weak fiber matrix interface is modeled numerically. Effects of interface properties and residual stresses incurred during the fabrication are addressed in detail. The computational modeling is guided by comparison with experimental data. The study provides an understanding which will be used to model the multiaxial behavior of weakly bonded composites and to provide a tool for predicting the failure of composite structures.     

Control of residual stresses affecting fatigue life of pulsed current gas-metal-arc weld of high-strength aluminum alloy

The influence of pulse parameters on residual stresses of the gas-metal-arc (GMA) weld of a 10-mm-thick extruded section of high-strength Al-Zn-Mg alloy has been analyzed. The role of pulse parameters affecting the residual stresses of the weld joint has been studied by considering a summarized influence of pulse parameters defined by a dimensionless factor ϕ=[(I _b /I _p ) ft _b ]. The reason for the variation in residual stresses of the weld joint with a change in ϕ under different mean currents (I _m ) has been studied by correlating the extent of weld metal deposition and weld size with the ϕ. It is observed that the increase of ϕ reduces the longitudinal and transverse stresses of the weld joint. The nature of variation in residual stresses of the weld joint with ϕ shows an agreement to the trend of variation in its size with ϕ. In conformation of an earlier work, it is proposed that the use of a pulsed current gas-metal-arc welding (GMAW) at proper pulse parameters giving desired ϕ may produce a weld joint having comparatively lower residual stresses with improved fatigue life than that of the weld joint produced by conventional GMAW process through its influence on weld size.     

Use of neutron and synchrotron X-ray diffraction for evaluation of residual stresses in a 2024-T351 aluminum alloy variable-polarity plasma-arc weld

The residual stress fields associated with variable-polarity plasma-arc (VPPA) welds in 2024-T351 aluminum alloy plates have been measured nondestructively using neutron and synchrotron X-ray diffraction. Neutron diffraction allows in-depth measurements of the full strain tensor to be made in thick components; synchrotron X-rays allow for rapid measurements of strains inside components, although their penetration is less than that of the neutrons and constraints arising from the diffraction geometry generally lead to only two strain components being easily measurable. Hence, a combination of the two techniques, applied as described herein, is ideal for a detailed nondestructive evaluation of residual stresses in plates. The residual stresses in a 12-mm-thick VPPA-welded aluminum 2024-T351 alloy plate have been measured using neutron diffraction. The stresses were then remeasured by a combination of neutron and synchrotron X-ray diffraction after the plate had been reduced in thickness (or, skimmed) to 7 mm by machining both sides of the weld, mimicking the likely manufacturing operation, should such welds be used in aerospace structures. A strong tensile residual stress field was measured in the longitudinal direction, parallel to the weld, in both the as-welded and skimmed specimens. There was only a slight modification of the residual stress state on skimming.     

Three-dimensional modelling of thermal residual stresses and mechanical behavior of cast SiC/A1 particulate composites

Thermal residual stresses developed during casting of SiC/aluminum particulate-reinforced composites were investigated as a function of cooling rate and volume fraction of particles using thermo-elastoplastic finite element analysis. The phase change of the matrix during solidification and the temperature-dependent material properties as the composite is cooled from the liquidus temperature to room temperature were taken into account in the model. Further, the effect of thermal residual stresses on the mechanical behavior of the composites was also studied. Based on the study, it was found that the matrix undergoes significant plastic deformation during cool down and has higher residual stress distribution as the cooling rate increases. The model which does not include the solidification of the matrix tends to overestimate the residual stresses in the matrix and underestimate the tensile modulus of elasticity of the composites. In addition, the presence of thermally induced residual stresses tends to decrease the apparent modulus of elasticity and increase the yield strength of the composites compared to those without residual stresses.