X-ray Diffraction Stress Analysis Research Articles

The effect of shot peening on the contact fatigue performance of C40 steel gears after laser surface melting

In this paper, shot peening (SP) was employed as a post-processing technique for the laser surface melted (LSMed) gear. The aim was to improve the contact fatigue performance of laser surface melting+shot peened (LSMSPed) gears. The microstructure, surface roughness, residual stress, microhardness of C40 steel gears before and after SP treatment were characterized using scanning electron microscopy, x-ray diffraction stress analyzer, contour measuring instrument, and hardness tester. Fatigue test of gear was carried out with a Forschungsstelle für Zahnräder und Getriebebau (FZG) testing machine. Following the laser surface melting (LSM) treatment, a molten layer was observed on the gear teeth surface. The experimental results indicated that SP induced a hardened layer with a certain thickness and plastic deformation on the surface of LSMed gears. Importantly, as the SP parameters increased, there’s a corresponding reduction in both the average grain diameter and the maximum grain diameter. The reduction was most pronounced when the shot diameter reached its maximum value. It’s worth noting that once the optimal threshold for SP parameters is surpassed, the residual compressive stress and microhardness on the LSMSPed gear surface do not exhibit a continuous growth trend. Furthermore, the rise in SP parameters resulted in a gradual increase in the surface roughness of LSMSPed gears, albeit to varying degrees. In light of the combined effects of grain refinement, residual compressive stress, microhardness, and surface roughness, the contact fatigue performance of LSMSPed gears improved with increasing SP parameters. Notably, when comparing the contact fatigue life of LSMed gears with that of LSMSPed gears, we observed a substantial enhancement. However, it’s essential to highlight that when the shot diameter reaches its maximum value, the contact fatigue life of the LSMSPed gear, somewhat unexpectedly, decreased. It emphasized to a certain extent the influence of surface roughness on the contact fatigue performance of LSMSP gears.

Residual Stress Testing and Simulation Analysis of Crystal Structures of Electronic Device Materials

In this paper, we analyze the residual stress of different components of the crystal structures of electronic device materials following exposure to elevated temperatures using a combination of experimental tests and finite element simulations. X-ray diffraction (XRD) and LXRD micro-area residual stress analyzer were employed to determine the residual strain and stress of the CBGA sample encapsulation cover and solder joints. Subsequently, the experimental data were utilized to verify the accuracy of the simulation. The discrepancy between experimental measurements and simulation outcomes of the residual stress following reflow soldering of CBGA-assembled micro-solder joints is below 14%. The analysis also included thermal warping deformation of the CBGA encapsulation cover and how the residual stress was influenced by the diameter, spacing, and height of the solder joints. The study reveals that the residual stress following reflow soldering of BGA solder joints is non-uniformly distributed within the array. Within a single solder joint, residual stress gradually increases in distribution from its middle to the point where it make contact with the PCB and chip, with the highest level of residual stress observed where the solder joint contacts the chip. The variation in material parameters, such as the coefficient of thermal expansion, is the primary cause of thermal warping deformation on the surface of CBGA encapsulation covers. Three primary factors significantly impact the residual stress on BGA solder joints: solder joint diameter, spacing, and height. The maximum value is inversely proportional to the height of the solder joints and the residual stress. Conversely, the diameter and spacing of the joints are positively proportional to the highest value. When the diameter of the solder joint is increased from 0.55 mm to 0.75 mm, the maximum residual stress in the BGA solder joint increases from 37.243 MPa to 36.835 MPa. Conversely, increasing the height of the solder joint from 0.36 mm to 0.44 mm reduces the stress from 39.776 MPa to 36.835 MPa.

Investigating the effect of laser shock peening on the wear behaviour of selective laser melted 316L stainless steel

Selective Laser Melting (SLM) is an emerging additive manufacturing technology that produces metallic parts with high customization. The applications of stainless steel 316L have been restricted owing to their poor tribological performance, especially in the as-printed condition. In this study, SLM-made SS 316L is subjected to laser shock peening (LSP), one of the surface modification techniques, to improve its characteristic microstructure, mechanical and wear behaviour. X-ray diffraction and residual stress analysis show that the laser shock peening promotes micro-level grain refinement and compressive residual stresses in the severely deformed layer, resulting in increased micro-hardness up to 22%. Pin on disk wear test is carried out, and the optimum condition is determined using the Taguchi method for the polished as-printed specimen. The wear rate of polished as-printed and laser shock peened specimens at optimized conditions were 2.4156 × 10−3 mm3 m−1 and 1.7871 × 10−3 mm3 m−1, respectively. The laser shock peened specimen showed higher wear resistance with a 26% reduction in wear rate compared to the polished as-printed specimens.

Effect of low annealing temperature on the structure and chemical order of Ni2MnGa thin films

Low temperature annealing effect on the structure, residual stress and local chemical order of Ni2MnGa alloys thin films were investigated by atomic force microscopy, x-ray diffraction and x-ray stress analyses as well as extended x-ray absorption fine structure. Thin films were prepared by sputtering on GaAs substrates maintained at room temperature and 300 °C during deposition. The samples prepared at 300 °C were subsequently annealed at 150 °C and 300 °C for one and half hour. X-ray diffraction measurements indicated both a development of crystalline texture in which austenite (110) crystalline planes are preferentially aligned parallel to the film plane as well as compressive residual stress, mainly induced by the accommodation of the film on the substrate surface and by heating-cooling in the growth process. Atomic force microscopy analyses reveal a surface morphology dominated by a topography of hillocks and peaked massifs, whose roughness increases by about twenty times with the increase in the crystalline texture induced by annealing at 300 °C of the samples. Interestingly, extended x-ray absorption fine structure analysis performed at Mn K-edge indicate that residual stress is preserved even after significant increase of the structural and chemical ordering induced by the low temperature annealing.

Effect of stress shot peening on the residual stress field and microstructure of nanostructured Mg-8Gd-3Y alloy

The effects of stress shot peening on the residual stress, microstructure and mechanical property of nanostructured Mg-8Gd-3Y alloy were systematacially investigated by the X-ray diffraction stress analysis, modified Williamson–Hall method, transmission electron microscopy and hardness tester. The results indicated that conventional shot peening led to a gradient nanostructured Mg-8Gd-3Y alloy with a size of 60–100 nm at the top surface layer. The formation of nanograins was primarily ascribed to the dynamic rotation recrystallization. Compared with conventional shot peening, stress shot peening significantly improved the residual stress distribution with a maximum value of −215 MPa and the affected depth. In parallel, stress shot peening conferred superior microstructures at the deformation layer, with smaller domain size, more severe lattice distortion and higher-density dislocations. Owing to inducing finer microstructures and higher compressive residual stresses, stress shot peening produced a stiffer deformation layer. It is concluded that stress shot peening was more potent in promoting the surface layer characteristics of nanostructured Mg-8Gd-3Y alloy than conventional shot peening.

Determination of surface mechanical property and residual stress stability for shot-peened SAF2507 duplex stainless steel by in situ X-ray diffraction stress analysis

In this study, SAF2507 duplex (austenite–ferrite) stainless steel was processed by shot peening. The depth–profile variations of the stress state and work hardening in the shot-peened layer were investigated by X-ray diffraction and microhardness tests. The evolutions of surface morphology and microstructure were investigated using scanning and transmission electron microscopy. The stress–strain relations of the shot-peened surface and surface residual stress relaxation caused by cyclic stresses were experimentally determined by in situ X-ray diffraction stress analysis combined with tensile tests. Results showed that shot peening (SP) has induced severe plastic deformation in the surface layer, with the attendant work hardening and high compressive residual stresses (CRS). Nevertheless, there were incompatibilities in plastic deformation between the phases, and more property improvements represented by higher CRS, peak breadth and microhardness were conferred into austenitic phases. SP notably enhanced the surface yield strength of this two-phase alloy. The surface yield strength σ0.2 of ferrite and austenite were around 780 and 1100MPa after SP, which were 59% and 104% respectively higher than that of the untreated surface. The surface stress relaxation under cyclic tensile loadings consisted of a two-stage process. The surface residual stresses relaxed dramatically within the first cycle (N=1), then decreased linearly with the logarithm of loading cycles (N>1). The more severely deformed microstructures in austenite resulted in higher surface yield strength and contributed to higher cyclic stability of residual stress.

Applying a combination of laboratory X-Ray diffraction and digital image correlation for recording uniaxial stress-strain curves in thin surface layers

By combining laboratory-based x-ray diffraction stress analysis with optical digital image correlation recorded in-situ during tensile loading, a new methodology has been developed to obtain for surface specific stress-strain curves. This novel methodology has been validated by comparing the reconstructed stress-strain curves from the x-ray diffraction/optical digital image correlation approach with stress-strain curves recorded using standard methods. The validated methodology enables now the recording of standard mechanical test data of altered surface layers, such as shot peened and machined surfaces or from proton-irradiated samples where the irradiated layer is limited to a depth of 10 s of microns.

Micro-Raman and X-ray diffraction stress analysis of residual stresses in fatigue loaded leached polycrystalline diamond discs

Polycrystalline diamond (PCD) cylindrical tool-bits used in oil well drilling are susceptible to fracture due to the hostile environment of randomly occurring high impact loads. These tool-bits generally comprise of a PCD layer sintered onto a Co-cemented tungsten carbide substrate. The cobalt metallic phase primarily aids the formation of the diamond to diamond bonds, however during application the same cobalt expands much quicker than the diamond, breaking the very same bonds it helped to form in the first place, leading to premature failure of the tool bits. As the PCD is virtually a two-phase material comprised of cobalt and diamond, substantial volumes of the metallic phase can be removed through a leaching process without compromising the cohesiveness of the diamond matrix, with reported improved wear resistance and thermal stability. X-ray diffraction and Raman spectroscopy techniques were used to investigate residual stresses in leached polycrystalline diamond disc samples. A systematic investigation and evaluation of the average in-plane residual stress fields using the Raman technique showed a progressive shift of the residual stress state from a compressive stress state to an average tensile stress state as a function of increasing number of loading cycles. In contrast the X-ray diffraction method recorded compressive stresses for all the measurements even at the highest number of loading cycles. The apparent disagreement between the two sets of results were satisfactorily explained by considering the probing beam size and sampling depth for the two different but complementary techniques.

Chemical order and residual stress analysis in Ni2MnGa alloys

Stoichiometric Ni2MnGa alloy thin films prepared by DC magnetron sputtering techniques on flexible glass substrates were investigated by X-ray diffraction (XRD) and X-ray stress analyses (XSA) measurements. Our results indicate that high degree of antisite chemical disorder in the as-deposited samples can be significantly reduced by moderate temperature anneals (<870 K) within a few minutes (<100 min) together with relaxation of residual strain. However, thermal cycles used during growth and annealing procedures can also reintroduce residual stresses caused by the mismatch of the linear expansion coefficients of the alloy and the substrate. Volume fractions determination of the austenite and martensite phases reveal the presence of retained martensite in amounts which reaches 35% in thermal treated thin films grown onto flexible glass. Our present study indicates that magneto-elastic devices based on NiMnGa alloy thin films must be carefully designed to extract their optimal performance.

Effect of Thickness of Molybdenum Nano-Interlayer on Cohesion between Molybdenum/Titanium Multilayer Film and Silicon Substrate.

Titanium (Ti) film has been used as a hydrogen storage material. The effect of the thickness of a molybdenum (Mo) nano-interlayer on the cohesive strength between a Mo/Ti multilayer film and a single crystal silicon (Si) substrate was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and nano-indenter. Four groups of Si/Mo/Ti multilayer films with different thicknesses of Mo and Ti films were fabricated. The XRD results showed that the introduction of the Mo layer suppressed the chemical reaction between the Ti film and Si substrate. The nano-indenter scratch results demonstrated that the cohesion between the Mo/Ti film and Si substrate decreased significantly with increasing Mo interlayer thickness. The XRD stress analysis indicated that the residual stress in the Si/Mo/Ti film was in-plane tensile stress which might be due to the lattice expansion at a high film growth temperature of 700 °C and the discrepancy of the thermal expansion coefficient between the Ti film and Si substrate. The tensile stress in the Si/Mo/Ti film decreased with increasing Mo interlayer thickness. During the cooling of the Si substrate, a greater decrease in tensile stress occurred for the thicker Mo interlayer sample, which became the driving force for reducing the cohesion between the Mo/Ti film and Si substrate. The results confirmed that the design of the Mo interlayer played an important role in the quality of the Ti film grown on Si substrate.

Effects of cutting conditions on the microstructure and residual stress of white and dark layers in cutting hardened steel

The microstructure and residual stresses of white and dark layers formed during a hard-cutting process have significant influence on the surface integrity of a workpiece. Therefore, the microstructure and residual stress of white and dark layers at low and high cutting speeds, along with different levels of flank wear are discussed, based on the experiment and simulation results. The orthogonal hard-cutting experiments on AISI 52100 steel were performed using polycrystalline cubic boron nitride (PCBN) inserts. A finite element model was developed to simulate the hard-cutting process. The microstructure and residual stress of the white and dark layers were analyzed through scanning electron microscopy, transmission electron microscopy, and an X-ray diffraction stress analyzer. The results indicate that the thickness of the white and dark layers is determined by the cutting heat and plastic strain in the subsurface. The grain size of the white and dark layers increases with cutting speed and flank wear. The formation mechanism of the dark layer changes from dynamic recovery to dynamic recrystallization with increase in flank wear. The residual compressive stress in the white layer at low cutting speeds is mainly caused by the microstructure of the white layer and plastic deformation, and the residual tensile stress in the white layer at high cutting speeds is mainly caused by the cutting heat. Tensile stress is induced in the white and dark layers when the workpiece is cut by a worn tool, and the tensile stress is caused by the high cutting heat and microstructure of the dark layer.

Growth of HfN thin films by reactive high power impulse magnetron sputtering

Thin hafnium nitride films were grown on SiO2 by reactive high power impulse magnetron sputtering (HiPIMS) and reactive direct current magnetron sputtering (dcMS). The conditions during growth were kept similar and the film properties were compared as growth temperature, nitrogen flow rate, and in the case of HiPIMS, duty cycle were independently varied. The films were characterized with grazing incidence X-ray diffraction (GIXRD), X-ray reflection (XRR) and X-ray stress analysis (XSA). HiPIMS growth had a lower growth rate for all grown films, but the films surfaces were smoother. The film density of HiPIMS deposited films grown at low duty cycle was comparable to dcMS grown films. Increasing the duty cycle increased the density of the HiPIMS grown films almost to the bulk density of HfN as well as increasing the growth rate, while the surface roughness did not change significantly. The HiPIMS grown films had large compressive stress while the dcMS grown films had some tensile stress. The dcMS grown films exhibit larger grains than HiPIMS grown films. The grain size of HiPIMS grown films decreases with increasing nitrogen flow rate, while the dcMS grain size increased with increasing nitrogen flow rate. This work shows that duty cycle during HiPIMS growth of HfN films has a significant effect on the film density and growth rate while other film properties seem mostly unaffected.

INFLUENCE OF ANNEALING ON THE DEPTH MICROSTRUCTURE OF THE SHOT PEENED DUPLEX STAINLESS STEEL AT ELEVATED TEMPERATURE

The depth profiles of residual stresses and lattice parameters in the surface layers of shot peened duplex stainless steel at elevated temperature were investigated utilizing X-ray diffraction analysis. At each deformation depth, residual stress distributions in both ferrite and austenite were studied by X-ray diffraction stress analysis which is performed on the basis of the sin[Formula: see text] method and the lattice parameters were explored by Rietveld method. The results reveal that difference changes of depth residual compressive stress profiles between ferrite and austenite under the same annealing condition are resulted from the diverse coefficient of thermal expansion, dislocation density, etc. for different phases in duplex stainless steel. The relaxations of depth residual stresses in austenite are more obvious than those in ferrite. The lattice parameters decrease in the surface layer with the extending of annealing time, however, they increase along the depth after annealing for 16[Formula: see text]min. The change of the depth lattice parameters can be ascribed to both thermal expansion and the relaxation of residual stress. The different changes of microstructure at elevated temperature between ferrite and austenite are discussed.

Characterization of Microscopic Stresses in a Polycrystalline Fe-Ga Alloy with Large Elastic Anisotropy

Fe-Ga alloys show large magnetostriction, which strongly depends on crystal orientation. This phenomenon is associated to some degree with large elastic anisotropy. In this study, white X-ray diffraction with micro-beam synchrotron radiation was used to evaluate the microscopic stresses evolved in a polycrystalline Fe-Ga alloy under tensile loading. In the analysis, the large elastic anisotropy of the Fe-Ga alloy was focused. The stress distribution in the alloy microstructure under tensile loading was estimated using a finite element method (FEM) simulation that considered the dependence of the elasticity on the crystal orientation. The crystal orientation of grains in the polycrystalline Fe-Ga alloy was measured using electron backscatter diffraction. The FEM simulation showed that the stress distribution in the microstructure depended on the crystal orientation. The X-ray diffraction stress analysis indicated that under tensile loading, the stresses in the alloy depended on the crystal orientation. This finding is similar to the results obtained from the FEM simulation, although the absolute values of the stresses may have reflected the effects of heterogeneous deformation on the stress distribution.

Residual Stress in Nb3Sn Superconductor Strand Introduced by Structure and Stoichiometric Distribution After Heat Treatment

Nb 3 Sn, a widely adopted superconducting material, suffers from fragility and sensitivity to strain. Many studies have anticipated these drawbacks to be greatly influenced by thermal expansion mismatch between the Nb 3 Sn superconducting phase and matrix. We conducted X-ray diffraction (XRD) stress analysis on a heat treated bronze strand at room temperature and found that its average axial residual stress was -135.7 MPa with fluctuation of about 300 MPa. We developed an elastic analytical model and explained the overall compression. The considerable stress fluctuation phenomenon may originate from diffusion, which was supported by electron probe microanalysis results. This work highlights the importance of volume transmutation and component distribution on the stress status of a superconducting strand and can supplement the thermal mismatch model.

Microstructure and mechanical properties of stress-tailored piezoelectric AlN thin films for electro-acoustic devices

Nanoindentation measurements along with atomic force microscopy, X-ray diffraction, and residual stress analyses on the basis of Raman measurements have been performed to characterize stress-tailored AlN thin films grown using reactive RF magnetron sputtering. The intrinsic stress gradient caused by the growing in-plane grain size along film thickness was minimized by increasing the N2 concentration in the Ar/N2 gas mixture during the growth process. The increase of N2 concentration did not degrade the device-relevant material properties such as crystallographic orientation, surface morphology, piezoelectric response, or indentation modulus. Due to comparable crystallographic film properties for all investigated samples it was concluded that mainly the AlN crystallites contribute to the mechanical film properties such as indentation modulus and hardness, while the film stress or grain boundaries had only a minor influence. Therefore, by tailoring the stress gradient in the AlN films, device performance, fabrication yield, and the design flexibility of electro-acoustic devices can be greatly improved.

Spatially resolved temporal stress evolution during laser surface spot hardening of steel

The time-dependent stress evolution, the resulting residual stresses as well as the microstructure of the heat treatable low alloyed steel AISI 4140 induced by laser surface spot hardening was investigated systematically by means of synchrotron X-ray diffraction. In‐situ stress analyses with a time resolution up to 100ms were carried out at the synchrotron beamlines P05@PETRAIII(*), DESY, Hamburg and PDIFF@ANKA, Karlsruhe, by the application of the measurement and evaluation approach for very fast X-ray diffraction stress analyses. During the laser surface spot hardening using a homogenization working optic with a spot size of approx. 8×8mm2 at a maximum temperature TA,max of 1150°C and heating/cooling rates vheat/cool of 1000 K/s time-resolved diffraction data were collected for various measurement positions inside and outside of the processed zone aiming to analyze the different origins for residual stress build-up. The in-situ tests were supplemented by X-ray residual stress analyses and microscopical investigations of the microstructure subsequent to the laser hardening process (ex-situ analyses).The results show that inside of the martensitic transformed region (process zone) in radial and in tangential direction homogeneous compressive residual stresses are generated. The data of the in-situ diffraction experiments reveal that these compressive residual stresses develop due to (i) local compressive elasto-plastic deformations and (ii) local phase specific transformation strains. Outside the process zone, the compressive residual stresses are balanced by rather high inhomogeneous tensile residual stresses. By means of the in-situ determined diffraction data it is proven that these tensile residual stresses have their origin in the superposition of (i) quenching effects outside the process zone, (ii) local elasto-plastic deformations and (iii) the effect of phase transformations in the nearby process zone.

X-ray diffraction analysis of residual stresses in textured ZnO thin films

Residual stresses are commonly generated in thin films during the deposition process and can influence the film properties. Among a number of techniques developed for stress analysis, X-ray diffraction methods, especially the grazing incidence set-up, are of special importance due to their capability to analyze the stresses in very thin layers as well as to investigate the depth variation of the stresses. In this contribution a method combining multiple {hkl} and multiple χ modes of X-ray diffraction stress analysis in grazing incidence set-up is used for the measurement of residual stress in strongly textured ZnO thin films. The method improves the precision of the stress evaluation in textured samples. Because the measurements are performed at very low incidence angles, the effect of refraction of X-rays on the measured stress is analyzed in details for the general case of non-coplanar geometry. It is shown that this effect cannot be neglected if the angle of incidence approaches the critical angle. The X-ray stress factors are calculated for hexagonal fiber-textured ZnO for the Reuss model of grain-interaction and the effect of texture on the stress factors is analyzed. The texture in the layer is modelled by Gaussian distribution function. Numerical results indicate that in the process of stress evaluation the Reuss model can be replaced by much simpler crystallite group method if the standard deviation of Gaussian describing the texture is less than 6°. The results can be adapted for fiber-textured films of various hexagonal materials.

Measuring stress variation with depth using Barkhausen signals

Magnetic Barkhausen noise analysis (BNA) is an established technique for the characterization of stress in ferromagnetic materials. An important application is the evaluation of residual stress in aerospace components, where shot-peening is used to strengthen the part by inducing compressive residual stresses on its surface. However, the evaluation of the resulting stress-depth gradients cannot be achieved by conventional BNA methods, where signals are interpreted in the time domain. The immediate alternative of using x-ray diffraction stress analysis is less than ideal, as the use of electropolishing to remove surface layers renders the part useless after inspection. Thus, a need for advancing the current BNA techniques prevails. In this work, it is shown how a parametric model for the frequency spectrum of Barkhausen emissions can be used to detect variations of stress along depth in ferromagnetic materials. Proof of concept is demonstrated by inducing linear stress-depth gradients using four-point bending, and fitting the model to the frequency spectra of measured Barkhausen signals, using a simulated annealing algorithm to extract the model parameters. Validation of our model suggests that in bulk samples the Barkhausen frequency spectrum can be expressed by a multi-exponential function with a dependence on stress and depth. One practical application of this spectroscopy method is the non-destructive evaluation of residual stress-depth profiles in aerospace components, thus helping to prevent catastrophic failures.

The Nature and Origin of “Double Expanded Austenite” in Ni-Based Ni-Ti Alloys Developing Upon Low Temperature Gaseous Nitriding

Gaseous nitriding of Ni-4 wt pct Ti alloy plates led to the development of double expanded austenite (γ N1 and γ N2) at the surface of the nitride plates. Grazing-incidence X-ray diffraction analysis demonstrated that the component γ N1 is located close to the surface and the component γ N2 is located at a certain depth below the specimen surface, in correspondence with a layered character of the nitrided zone beneath the surface as revealed by optical microscopy. Electron probe microanalysis, atom probe tomography, and Laue microdiffraction analysis did not reveal a significant difference in nitrogen content of the γ N1 and γ N2 sublayers. By X-ray diffraction stress analysis it was shown that the only significant differences of the two expanded austenite layers is a pronounced difference in compressive stress parallel to the surface: the γ N1 layer is subjected to a huge compressive stress, as large as a few GPa, whereas a relatively modest stress prevails in the γ N2 layer.