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Abstract: The application of shot-peening to improve performance and reduce scatter in the high cycle fatigue regime is common in aerospace production practice. Frequently, aerospace components are re-shot-peened during refit to “restore” compressive stresses that may have redistributed in service. Since shot-peening is an impact process that can cause various surface artifacts, it is not clear what effect this re-shot-peening process has on fatigue properties. In the current study, the effects of shot-peening and re-shot-peening on the profile of surface residual stress and the four-point bend fatigue behavior of Ti–6Al–4V(wt.%) alloy were investigated at room temperature and 150°C. A step-test method was used to determine the fatigue strength of the shot-peened and re-shot-peened specimens in different conditions. Shot-peening improved the fatigue strength of the alloy from about 65% σ y to 71% σ y (σ y is the yield strength of this alloy at room temperature). The fatigue limits of the shot-peened Ti–6Al–4V alloy at room temperature and 150°C were found to be almost identical. Residual stresses did not seem to redistribute significantly under the fatigue loading at room temperature and 150°C. Both shot-peening and re-shot-peening significantly enhanced the fatigue strength over that of the un-shot-peened alloy. No negative effects of re-shot-peening were observed. [Copyright &y& Elsevier]

Abstract: Cylindrical, flat-nose, 4340 steel projectiles (2.0cm height) were impacted onto Ti–6Al–4V targets (2.5 thick) at velocities ranging from 633 to 1027m/s. Plug formation was observable at 633m/s and exited the target between 1006 and 1027m/s. Adiabatic shear bands (ASBs) composed of dynamically recrystallized (DRX) grains and cracks formed both vertically and horizontally (parallel or perpendicular) to the impact axis. The ASB characteristically white-band thickness varied from 5 to 40μm, with the thicker bands occurring at the highest impact velocity. ASBs and cracks increased in frequency with increasing impact velocity, forming a cylindrical flow regime characterizing the plug. TEM analysis showed a greater than order of magnitude decrease in the DRX regime composing the ASBs, while EBSD analysis showed a residual DRX, grain-size regime varying from 50 to 900nm. There was no evidence for an α→β transformation occurring within the ASB/DRX regime. [Copyright &y& Elsevier]

Abstract: The quasi-static compressive mechanical behavior and deformation mechanism of closed-cell aluminum foam were researched, and the effect of cell diameter of aluminum foam on compressive and energy absorption properties was also discussed. Results show that the compressive process of closed-cell aluminum foam is characterized by three deformation stages: linear elastic stage, plastic collapse stage and densification stage. The effect of cell diameter on its compressive property is obvious: with the increasing cell diameter, the peak stress (σ 0) and nominal Young''s modulus (E 0.2) increase, energy absorption capability increases, however the energy absorption efficiency decreases and becomes more and more unstable. At the same time, the compressive specimen is also affected by the size effects obviously: when L/d ≥6, the compressive property of closed-cell aluminum foam is reproducible. [Copyright &y& Elsevier]

Abstract: Eight different Cr3C2–NiCr coatings doped with rare earth oxide were deposited with supersonic plasma spraying. Surface contact profiler, X-ray diffractometer, environmental scanning electron microscopy, multi-functional tribometer, microhardness tester were employed to investigate the microstructure and friction and wear performance of sprayed coatings. The results show that the wear volume loss of coatings doped with 2wt.% La2O3 and 2wt% La2O3 +2wt.% CeO2 is three orders of magnitude smaller than that of the coating without rare earth, respectively, correspondingly the friction coefficient of two coatings is only two third of that of the coating without rare earth. According to the SEM worn surface observations, the wear mechanism of the coating doped with 2wt% La2O3 is strain crushed wear induced by plastic deformation and fatigue during the sliding process, which is distinct with abrasive wear and delamination fracture wear mechanisms of the coating without rare earth. Furthermore, rare earth can make the microstructure more compact, less porous and denser, leading to the increase of average microhardness and decrease of its fluctuation range of sprayed coatings. [Copyright &y& Elsevier]

Abstract: Equal channel angular extrusion (ECAE) is an effective forming technique that increases the material strength by accumulating plastic strain into the workpiece without changing its cross-sectional shape in the multi-pass processing. This study concentrates on the investigation of interface contact phenomenon between the workpiece and channel in terms of forming load and material flow predictions. The change of contact conditions during remeshing was also investigated in terms of variation of load requirements and volume losses. In order to validate the numerical algorithm proposed, simulation results were compared with the experimentally measured data of the ECAE with the CP-Ti Gr-1 cylindrical specimen. Numerical simulations were obtained by applying the mixed finite element formulation with tetrahedral elements under the non-isothermal condition. For determination of the material data, compression test was carried out and the tested data was interpolated as a function of strain, strain rate and temperature. The current investigation clearly showed the importance of proper handling of the friction boundary condition during numerical simulations to guarantee the solution accuracy of the ECAE. [Copyright &y& Elsevier]

Abstract: Ultrasonic cold forging technology (UCFT) utilizing ultrasonic vibration energy is a method to induce severe plastic deformation to a material surface, therefore, the structure of the material surface becomes a nano-crystal structure from the surface to a certain depth. It improves the mechanical properties; hardness, compressive residual stress, wear and fatigue characteristics. Applying UCFT to a rolling process in the steel industry is introduced in this study. First, the UCFT specimens of a tool steel (SKD-61/equivalent H13) are prepared and tested to verify the effects of the UCFT in a variety of mechanical properties, the UCFT is applied to the trimming knives in a cold rolling process. It has been determined that UCFT improves the mechanical properties effectively and becomes a practical method to improve productivity and reliability by about two times compared with the conventionally treated tooling in the trimming process in a cold rolling line. [Copyright &y& Elsevier]

Abstract: We have studied penetration processes of liquid gallium into 2017 aluminum alloys by measuring Rayleigh-wave velocity and attenuation using laser-generated ultrasound. The gallium penetration is the initial stage of liquid-metal embrittlement, which is reduction in the elongation to failure that can be produced when normally ductile solid metals are stressed while in contact with a liquid metal such as gallium. The results for samples without annealing showed that the Rayleigh-wave velocity decreased a few percent in the time scale of 103 s, suggesting an extraordinarily rapid penetration of gallium along subsurface. The results for annealed samples showed decrease in the time scale of 104 s. The difference in the penetration rates suggests that residual stress may facilitate the penetration of gallium. [Copyright &y& Elsevier]

Abstract: The effects of fatigue and fretting fatigue on the distribution of residual stresses in shot and laser shock peened Ti–6Al–4V samples have been investigated. Residual elastic strains have been determined using high-energy synchrotron X-ray diffraction. Laser shock peening introduces a considerable compressive residual stress, the compressive zone extending 1.5mm below the surface. The effects of fatigue loading have been investigated using a notched three-point bend geometry. The residual stress field was found to be largely insensitive to fatigue cycling, at least for the applied stress range studied. For fretting fatigue, while the residual stresses at depth were little affected, within 0.5mm of the surface significant stress relaxation was observed; the extent of relaxation being greatest in the direction parallel to the fretting direction. The states of residual stress have been quantified using the concept of eigenstrain, which quantifies the retained plastic misfit resulting from peening. Finite element modeling has been used to determine the eigenstrain profiles causing the measured elastic strain profiles, and the changes to these eigenstrain profiles due to fretting. Our results suggest laser shock peening confers much greater fretting fatigue resistance than traditional shot peening alone due to the much deeper compressive zone. [Copyright &y& Elsevier]

Abstract: Thermal residual stress analysis and failure simulation of particle-reinforced composites are performed based on thermomechanics and the finite element method (FEM) to investigate the effects of particles on strength and toughness. It is discovered that the residual stresses in matrix are controlled mainly by adjacent particles via stress superposition, and an expression for the residual stress is derived. The size of the residual stress zone in the matrix is found to increase with the particle size. The FEM failure simulation in uniaxial tension reveals two features: (i) the residual stress caused by the second phase particles in ceramic matrix would lead to strength degradation due to the weakest link theory; (ii) the second phase particles in the composite may enhance the fracture toughness because of the crack arrest and crack-deflection caused by residual compressive stress. These features have been confirmed by experimental results of TiN/Si3N4 composite. [Copyright &y& Elsevier]

Abstract: A unique approach introducing sialon polytypoids as a functionally graded material (FGM) bonding has been used to join silicon nitride and alumina. The various multilayered FGM samples ranging from 3 to 20 layers were sintered to fabricate a crack-free joining of heterogeneous ceramics. To calculate thermal stresses for the various multilayered FGM samples, the finite element analysis program (FEAP) was used. These analyses results matched experimental results and showed why some samples had large residual stresses that resulted in fracture. Moreover, the electron probe X-ray microanalysis (EPMA) from a crack-free FGM sample had a smooth concentration profile, which verifies the interface diffusion during sintering at each graded layer and confirms a successful joining. [Copyright &y& Elsevier]

Abstract: TiPdNi thin films with less than 2μm thickness were produced using ion beam assisted deposition (IBAD) on heated and unheated substrates. Films deposited on unheated substrates were found to be amorphous, and subsequently annealed to induce crystallization. Residual stresses in the films were evaluated using the Stoney equation after deposition, and after annealing. Films deposited using IBAD on unheated substrates were found to have slight compressive stress (−22.4MPa) while films deposited on heated substrates had a moderate tensile stress (176.2MPa). Annealed films experienced extensive tensile stress (598.3MPa), resulting in film failure. [Copyright &y& Elsevier]

Abstract: Commercially pure titanium was sandblasted with SiO2 particles of 200–300μm in diameter. It was found that the sandblasted samples exhibited an increase in fatigue strength by 11% over that of the untreated samples. The peak subsurface compressive residual stress produced by sandblasting was measured by XRD to be around 480MPa. Three distinct regions were observed in the sandblasted samples, namely the severely deformed surface layer, the region deformed mainly by twinning, and the substrate. After recovery treatment below 300°C, the surface layer of the sandblasted samples was transformed into a nano-crystalline structure, and its corrosion resistance was significantly improved. [Copyright &y& Elsevier]

Abstract: A novel fracture mechanics technique has been employed for the determination of crack growth rate and threshold stress intensity factor (K Iscc) for stress corrosion cracking (SCC) using small circumferential notch tensile (CNT) specimens. The technique was applied successfully for testing SCC susceptibility of spheroidal graphite (SG) cast iron in 5M NaOH at 100 and 120°C. Crack growth rate of SG cast iron in 5M NaOH solution at 100 and 120°C has been determined at different stress intensity factors (K I), and the K Iscc have been determined to be 11.2 and 9MPam1/2, respectively. The surfaces of fractured specimens have been examined by scanning electron microscopy (SEM) in order to establish intergranular propagation of stress corrosion cracks. CNT testing is a simple, relatively fast and cost-advantageous approach for generating crack growth rate and K Iscc data. [Copyright &y& Elsevier]

Abstract: The present paper addresses the accuracy of the reconstruction of depth profiles from X-ray diffraction lattice-strain analysis, combined with successive sublayer removal. In order to test the accuracy of reconstruction irrespective of experimental inaccuracies, X-ray diffraction was simulated for model stress-depth profiles and/or composition-depth profiles, reflecting those obtainable with surface engineering of materials, i.e. shot peening, carburizing of austenite and low temperature nitriding of stainless steel. Two principally different methods for the reconstruction of the actual stress and composition profiles were compared: [(I)] assuming that the lattice parameter determined at a specific depth, for a specific value for ψ is a weighted average over the actual lattice spacing profile for this ψ-direction; [(II)] assuming that the stress/strain determined at a specific depth is a weighted average over the actual stress/strain depth profile. On the basis of the results it is concluded that method (I) virtually avoids the occurrence of ghost stresses (stress artefacts) upon data evaluation. Substantial ghost stresses may occur upon data analysis using method (II) for strongly compositionally graded materials. [Copyright &y& Elsevier]

Abstract: The isothermal creep resistance of AlSi12CuMgNi alloys produced by squeeze casting, unreinforced and reinforced with 10, 15 and 20vol% of short alumina fibres is investigated by means of long-term tensile creep tests at 300°C. Dislocation creep-mechanisms associated with a Norton exponent n =3 are attributed to both the unreinforced and the short fibre reinforced materials (SFRMs) in the stress range between 10 and 50% of the yield strength at 300°C. The embedding of short fibres reduces the creep rate of the alloy by more than one order of magnitude. The SFRM with 15vol% of reinforcement is the most creep resistant, while the 20vol% SFRM is less creep resistant than the 10 and 15vol% SFRMs due to its higher defect density and larger interface area. Load changes are imposed during creep tests to study the influence of periods of overloading. Returning to the initial load causes the stationary creep rates of the SFRMs to be further reduced down to one third of their initial values. Furthermore, a small increase in the creep exponent n of the SFRMs is observed after an overloading cycle. The increase of the connectivity of the Si/Al2O3-short fibre network in the direction of loading enhances the load transfer effect from the matrix to the reinforcement decreasing thus the external stress acting on the matrix. The yielding of highly stressed zones in the matrix around the ceramic reinforcement during the overload is able to produce a more uniform distribution of internal stresses when returned to a lower stress level. Both effects are considered to be responsible for the observed reduction of the stationary creep rate. The unexpected low creep resistance of the 20vol% SFRM in comparison with the two other composites can be explained by the larger number of micro-structural defects (≤1vol% porosity) found in this material after the infiltration process. Although the small portion of these defects does not affect the high temperature tensile properties of the composite, it accelerates the diffusion controlled creep mechanisms. The larger interface area present in the materials with higher reinforcement volume fraction increases the diffusivity as well. The connectivity of the Si/Al2O3-short fibre (SF) network is higher for the 20vol% SFRM than for the other SFRMs already before creep exposure. Thus the training effect by overloading periods is less efficient in the 20 vol% SFRM than in SFRMs with less fibre content. Those effects are counteracted by the fact that the higher the reinforcement volume fraction the smaller the load acting on the matrix. Yet for the investigated 20vol% SFRM samples, the negative contributions prevail resulting in a lower creep resistance than for the other two composites. [Copyright &y& Elsevier]

Abstract: Several methods have been suggested for deriving indentation flow curves using the instrumented indentation technique, in which true stress and true strain are defined with indentation parameters. The definition of true stress is nearly the same in all methods, but the definitions of true strain fall into two categories, sine function and tangent function. We adopted the work-hardening exponent to determine the definition appropriate in obtaining accurate indentation flow curves. The work-hardening exponent was proven to be affected only by the definition of true strain and not by other parameters when the effect of real contact depth was eliminated using finite element analysis. The sine function yields too large work-hardening behaviors for materials that obey power-law work-hardening, but the tangent function evaluates them accurately. The definition based on the tangent function was thus determined to be more appropriate in deriving the indentation flow curve. [Copyright &y& Elsevier]

Abstract: Highly damage tolerant hybrid syntactic foams are developed by using rubber and nanoclay particles to modify the matrix microstructure in syntactic foams. Four different types of glass hollow particles (microballoons) with different densities are used to fabricate the foam samples. In the rubber hybrid foams, 40 and 75μm size rubber particles are used by 2% by volume quantity. In nanoclay hybrid foams, volume of nanoclay particles is maintained at 2 and 5%. The total volume of all types of particles is maintained at 65% in all types of plain and hybrid syntactic foams. The plain and hybrid syntactic foams are characterized for flexural properties. An increase in flexural strength is observed with the incorporation of rubber particles in syntactic foams. In nanoclay hybrid foams, flexural strength is observed to depend on the nanoclay volume fraction. The strength of microballoons plays an important role in determining the fracture mode of plain and hybrid syntactic foams. Rubber particles are found to increase the energy absorption under the flexural loading conditions. [Copyright &y& Elsevier]

Abstract: Polyamide 6 intercalated/exfoliated (PIE) cements are fabricated and characterized. With the reinforcing nanointerphase, the flexure strength of a PIE cement is higher than that of ordinary cements by an order of magnitude. The optimum nanointerphase content is around 10wt.%. This technique has great potential in developing advanced precast and repair technologies. [Copyright &y& Elsevier]

Abstract: The effects on dislocation glide of the substitutional element copper in solution in α-iron are being investigated by computer simulation. In the first phase, the critical stress for a 〈111〉 {110} edge dislocation to overcome configurations of either a single or two nearest-neighbour solute atoms is simulated. Molecular statics and dynamics methods are used to simulate effects at temperature equal to and greater than 0K, respectively. Single copper atoms and nearest-neighbour pairs in the first atomic plane below the glide plane give the strongest barrier to dislocation glide, in partial agreement with elasticity theory. In addition to temperature, obstacle-spacing effects are considered. [Copyright &y& Elsevier]

Abstract: The atomic displacement fields of dislocation loops of size 1–5nm formed by self-interstitial atoms in α-Fe have been calculated using isotropic elasticity theory and anisotropic elasticity theory, and compared with atomic simulations for loops formed by 43–275 self-interstitial atoms. The atomic displacements predicted by anisotropic elasticity theory were in good agreement with those given by the atomistic simulations at distances greater than 3nm from the loop plane, but the displacements predicted by isotropic elasticity theory showed significant discrepancies at distances up to 15nm. [Copyright &y& Elsevier]

Abstract: A comprehensive coupled thermal-stress mathematical model, based on the commercial finite element (FE) package ABAQUS™, 1 [1] ABAQUS is a registered trademark of ABAQUS, Inc., Pawtucket, RI. has been formulated to describe thermal and stress–strain fields during the start-up phase of the direct chill (DC) casting process for AA5182 aluminum ingots. The computational domain includes industry-scale ingot and bottom block geometries. The heat transfer analysis incorporates the thermal boundary conditions that describe primary cooling via the mold, secondary cooling via the chill water, and ingot base cooling. To quantify the extent of secondary cooling, boiling curves that are a function of ingot surface temperature, water flow rate, impingement point temperature, and position relative to the point of water impingement have been used. Other complex heat transfer phenomena including water ejection on the vertical faces of the ingot, and water incursion into the gap at the base of the ingot have also been accounted for. The stress analysis employs a temperature dependent elastic rate-dependent plastic material constitutive behavior to quantify the stress and strain fields inside the ingot. The model has been validated against temperature and displacement measurements obtained from two 711mm×1680mm AA5182 ingots, cast under different start-up conditions (non-typical “cold” practice and non-typical “hot” practice). The stress analysis was further validated by residual stress data obtained from the cold cast ingot. Comparison of the model predictions with the industrial and laboratory data indicates that the model is capable of satisfactorily simulating aspects of the thermomechancial behavior of the ingot during the start-up phase. The model has been applied in a preliminary way to analyze the problem of hot tearing in ingots during the startup phase. The need for further refinement of the mesh has been identified. [Copyright &y& Elsevier]

Abstract: Dry sliding wear and tensile studies have been conducted on Al–7Si alloy after various melt treatments like grain refinement and/or modification. Combined grain refinement and modification not only increases the tensile strength and wear resistance but also significantly enhances the load bearing capacity of the alloy during dry sliding wear. The paper attempts to correlate the microstructural changes in the alloy on grain refinement and modification to the wear and tensile properties. [Copyright &y& Elsevier]

Abstract: The roles of specimen thickness and hardening behavior of the material on the ductile tearing resistance of a 6056 aluminum alloy are investigated separately as a function of stress triaxiality, by varying both the heat treatment (overaging or annealing + slow cooling) and the specimen geometry. The fracture path can be slanted or flat. Results show that increasing hardening capability and specimen thickness favors flat fracture. For the overaged material, the energy dissipation rate, measured on Kahn specimens, reaches a maximum value for an intermediate value of thickness (3.2 mm), whereas for the annealed material, a change in the fracture mode (from slanted to flat) induces a continuous increase in toughness with increasing thickness up to 6 mm. [Copyright &y& Elsevier]

Abstract: There is a growing demand in hard turning industry to produce favorable surface integrity (surface finish, microstructure, microhardness, and residual stress) for improving component performance. Suitable process parameters will produce certain favorable surface integrity or at least avoid detrimental phase transformations to component performance. It is not clear if surface integrity is controllable using a set of selected process parameters. This research is to study the feasibility of obtaining four distinct types of surface integrity, which may have potential dramatic effects on fatigue life of hard-machined components. This study identifies surface integrity first and follows with the necessary conditions possible to create it in hard turning. Favorable surface integrity for optimal fatigue life can be produced using small feeds and sharp cutting tools. From the process point of view, tool wear is the dominant factor to promote white layer formation and yields a large variance of surface roughness, which may significantly deteriorate component life. A white layer could be more than 30% harder and a dark layer about 60% softer than the bulk material. [Copyright &y& Elsevier]

Abstract: Mechanical properties of NiO films developed at approximately 800°C in air for 26h on a 99.9% pure polycrystalline Ni substrates have been investigated by X-ray diffraction, transmission electron microscopy and atomic force microscopy. The oxide layers, 8μm thick, exhibit a duplex structure with a slight {111} texture. The average stresses in the oxide films have been deduced by X-ray diffraction to be 330±35MPa in compression. Detailed analyses of the oxide films performed by atomic force microscopy show surface undulations on the nanometer scale located in some of the grains. These well-defined periodic structures are due to high growth stress heterogeneity from grain to grain in the oxide layer. From a linear analytical model, it is deduced that growth stresses as large as 4GPa can be developed locally during the high temperature oxidation process as a result of the strong in-plane anisotropy. [Copyright &y& Elsevier]

Abstract: Closed-loop controlled isothermal ‘constant-strain’ stress relaxation tests (SRT) at different strains led to the conclusion that SRT cannot provide the anticipated viscous strain rate over a wide stress range; the stress exponent for power-law creep was found to depend on strain. The recovery phase after SRT showed that delayed elasticity, not the viscous flow, controls relaxation processes during the primary stages of stress relaxation irrespective of the level of constraint. Viscous flow controls stress relaxation only at longer times exhibiting ‘apparently’ asymptotic approach to a quasi-stable stress rate. Limitations of SRT can be explained by formulating the relaxation processes on the basis of a three-component rheological equation, derived from independent isothermal constant-stress strain relaxation and recovery tests (SRRT). Theoretical predictions were made for the time-dependent recoverable (delayed elastic) and permanent components of strain as functions of time and imposed strain. Experimental results exhibiting the short-coming of conventional experimental and analytical approaches and the strength of present formulations are illustrated by using a titanium-based, α–β, Ti–6Al–2Sn–4Zr–6Mo alloy at 600°C (0.45Tm) as a test material. [Copyright &y& Elsevier]

Abstract: This study was performed in order to investigate the fatigue characteristics of nitrided SACM 645 steel according to the nitriding condition and notch shape. V-notches were made on the specimens and they were nitrided using the Nitemper method. The rotary bending fatigue test for each specimen was carried out at room temperature. The fatigue characteristics of the nitrided specimen improved compared with those of the non-nitrided specimen because of compressive residual stress on the surface. The improvement of the fatigue characteristics of the notched specimen was more effective than the smooth one. [Copyright &y& Elsevier]

In this study, fracture toughness (J-integral) values in cracked welded nodular iron were determined experimentally, and stress–strain analyses were done by the finite element method, for different crack sizes and locations with various strength levels. As a result, the effect of yield strength mismatch on the constraint around crack tip was discussed by means of stress triaxiality (ST) and plastic strain. It was found that ST values increase with crack length. Different regions in the weldment affect the extent of plastic deformation in the material. [Copyright &y& Elsevier]

Steels can be designed to exploit the coordinated motion of atoms during the bainite and martensite reactions. In this way, it has been possible to make exceptionally strong and tough alloys in bulk form, and at an affordable price. Crystal sizes can be reduced to between 20 and 180 nm, by annealing heterogeneously deformed martensite, or by forming bainite under conditions where there is no atomic mobility.Engineering failures are dominated by fatigue, the effects of which are exacerbated by welding and the associated residual stresses. Alloys can now be designed such that the deformation caused by transformation eliminates residual stresses, with extraordinary improvements in the fatigue life of constrained assemblies of metal. These important achievements are described here, within a framework which relates the atomic mechanism to the engineering scale. [Copyright &y& Elsevier]

Abstract: The anisotropic compressive behavior of closed-cell Al–Si alloy foams prepared by melt foaming process has been investigated. The results show that the stress drop ratio measured in the longitudinal direction is higher than that in the transverse direction. Moreover, the stress drop ratio decreases with increasing relative density of foamed specimen. The shape anisotropy ratio R increases firstly and decreases afterward with increasing relative density. The Young''s modulus ratio and yield stress ratio for closed-cell Al–Si alloy foams were investigated and compared with G&A model. A linear relationship between Young''s modulus ratio, yield strength ratio and anisotropy ratio has been obtained. The Young''s modulus is more sensitive to cell shape than yield stress. [Copyright &y& Elsevier]

Abstract: Proprietary equipment for mechanical testing at ultra-high temperatures by ohmic heating is outlined. Strain is measured with a video extensometer with an accuracy of up to . Stability and accuracy of the test system are evaluated on Pt- and refractory alloys. These specially designed and built test facilities are compared to commercially available high-vacuum test chambers with tungsten heater. [Copyright &y& Elsevier]