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Showing papers on "Hardening (metallurgy) published in 2010"


Journal ArticleDOI
TL;DR: In this article, the authors reviewed the S-phase surface engineering of stainless steels, Co-Cr alloys, and Ni-cr alloys and paid particular attention to the structure, formation conditions, supersaturation, hardening mechanisms and metastability of these materials.
Abstract: Stainless steel, Co-Cr and Ni-Cr alloys have played an important role in many industrial sectors to combat environmental degradation. However, low hardness and poor wear properties have impeded their tribological and tribochemical applications. Conventional thermochemical treatments can be used to significantly harden these passive alloys but at the expense of their corrosion resistance due to precipitation induced depletion of Cr in the matrix. Research in 1980s led to the discovery of a new expanded austenite phase, i.e. so called S-phase with combined improvement in wear and corrosion resistance. Recent research has revealed that S-phase can be formed not only in stainless steels but also in Co-Cr alloys and Ni-Cr alloys. It is the purpose of this paper to critically review the S-phase surface engineering of stainless steels, Co-Cr alloys and Ni-Cr alloys. Particular attention will be paid to the structure, formation conditions, supersaturation, hardening mechanisms and metastability of...

366 citations


Journal ArticleDOI
TL;DR: In this article, a pin-on-disk wear testing of nanocrystalline Ni-W alloys with grain sizes of 3-47nm has been carried out and the extreme conditions produced during sliding wear are found to result in structural evolution and a deviation from Archard scaling for the finest grain sizes; in the finest nanocrystine materials wear resistance is higher than would be expected based on hardness alone.

284 citations


Journal ArticleDOI
TL;DR: In this article, the deformation behavior of high-purity polycrystalline α-titanium under quasi-static conditions at room temperature was investigated, and a new anisotropic elastic/plastic model was developed to describe the macroscopic response of the aggregate.

258 citations


Journal ArticleDOI
TL;DR: In this paper, the authors use a rule of mixtures model to characterize the individual and the superposed contributions of two major mechanisms of crystal plasticity, i.e., Orowan strengthening and forest hardening.

256 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present a complete experimental data set for conventional Al-5083 H-131, with primary alloying element Mg (4.77) and secondary element Mn (0.68) in compression over a range of strain rates (10−4−6000 s−1) at room temperature.
Abstract: Recent improvements in strength and ductility of 5083 aluminum alloys have been obtained through the development of complex microstructures containing either reduced grain sizes (ultra-fine and nano-grained materials), grain size distributions (bimodal microstructures), particle reinforcements, or combinations of the above. Optimization of such microstructures requires an understanding of the conventional, coarse-grained basis alloy. We present here a complete experimental data set for conventional Al-5083 H-131, with primary alloying element Mg (4.77 wt%) and secondary element Mn (0.68 wt%) in compression over a range of strain rates (10−4–6000 s−1) at room temperature. The various strengthening mechanisms in Al-5083 are explored, including solute strengthening, precipitate hardening, strain hardening, strain rate hardening, and strengthening due to dislocation sub-structures. Previous experiments found in the literature on Al–Mg binary alloys allow us to calculate the solute strengthening due to Mg in solid solution, and TEM analysis provides information about precipitate hardening and dislocation cell structures. A basic strength model including these strengthening mechanisms is suggested.

254 citations


Journal ArticleDOI
TL;DR: In this paper, the authors studied how temperature, from the ambient temperature to 900°C, affects the mechanical properties of Al 0.5 CoCrCuFeNi alloys in different wrought states.

229 citations


Journal ArticleDOI
TL;DR: In this article, the tensile deformation behavior and microstructural evolutions of twinning induced plasticity (TWIP) steel with the chemical composition of Fe-31Mn-3Al-3Si and average grain sizes in the range of 21-726μm have been analyzed for each grain size, the Hollomon analysis and also the Crussard-Jaoul analysis as an alternative method to describe the work hardening behavior were investigated.

198 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of cooling rate on the high strain rate behavior of hardened boron steel was investigated and the results showed that the failure mechanism transformed from a ductile-shear mode at lower cooling rates to a shear mode in the high cooling rates.

175 citations


Journal ArticleDOI
TL;DR: In this article, the dielectric response of hard and soft Pb(Zr0.58Ti0.42)1−xMexO3 (Me=Fe or Nb) ceramics was studied at subswitching conditions over a wide range of temperatures (50 −450°C) and frequencies (10 mHz to 10 kHz).
Abstract: The dielectric response of hard (Fe-doped) and soft (Nb-doped) rhombohedral Pb(Zr0.58Ti0.42)1−xMexO3 (Me=Fe or Nb) ceramics was studied at subswitching conditions over a wide range of temperatures (50–450 °C) and frequencies (10 mHz to 10 kHz). The results show qualitative differences in the behavior of the acceptor- and donor-doped samples. Hard materials exhibit a steep increase in the complex permittivity with decreasing frequency. The onset of the dispersion is thermally activated with activation energies of about 0.6–0.8 eV and is attributed here to oxygen vacancy hopping. The activation energy for ac conductivity observed in soft materials is estimated to be about 1.7 eV, corresponding to half of the energy gap of Pb(Zr,Ti)O3 and is thus consistent with electronic conduction. The relevance of ionic hopping conductivity in hard materials to ferroelectric aging/deaging and hardening is analyzed. Strong ionic conductivity in hard samples and its absence in soft samples agree well with the dipolar mecha...

146 citations


Journal ArticleDOI
TL;DR: In this paper, an elasto-plastic self-consistent polycrystal model is extended to account, in an approximate fashion, for the kinematics of large strains, rigid body rotations, texture evolution and grain shape evolution.

144 citations


Journal ArticleDOI
TL;DR: In this paper, the effects of secondary elemental Mo or Ti addition in Al 0.3 CoCrFeNi alloy on age hardening at 700°C were investigated, and three FCC-structured high-entropy alloys were synthesized in order to investigate the effect of secondary element addition on age hardness.

Journal ArticleDOI
TL;DR: In this paper, the influence of constitutive modeling for springback simulations is analyzed for four different materials in the rolling-, transverse, and diagonal directions of a simple U-bend.

Journal ArticleDOI
TL;DR: Using molecular-dynamics simulation, this article simulated nanoindentation into the three principal surfaces of Cu and Al in the elastic regime, the simulation data agree fairly well with the linear elastic theory of indentation into an elastically anisotropic substrate with increasing indentation depth.
Abstract: Using molecular-dynamics simulation we simulate nanoindentation into the three principal surfaces—the (100), (110), and (111) surface—of Cu and Al In the elastic regime, the simulation data agree fairly well with the linear elastic theory of indentation into an elastically anisotropic substrate With increasing indentation depth, the effect of pressure hardening becomes visible When the critical stress for dislocation nucleation is reached, even the elastically isotropic Al shows a strong dependence of the force-displacement curves on the surface orientation After the load drop, when plasticity has set in, the influence of the surface orientation is lost, and the contact pressure (hardness) becomes independent of the surface orientation

Journal ArticleDOI
TL;DR: In this article, an enhanced precipitation-hardening response of Mg-0.5Ca (wt.%) alloy by microalloying with Al was reported, which is associated with the dense precipitation of ordered monolayer Guinier-Preston zones and the subsequent formation of Al2Ca causes the over-aging.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the mechanisms of corrosion and wear improvements by low energy high current pulsed electron beam (LEHCPEB) for an AISI 316-L steel.

Journal ArticleDOI
TL;DR: In this article, the effect of the objective derivatives and the equivalent stresses on the plastic flow anisotropy and the hardening evolution with damage is considered using a thermodynamically consistent framework.

Journal ArticleDOI
TL;DR: It is shown that reconstituted networks of crosslinked, bundled actin filaments harden when subject to cyclical shear, and exhibit a mechano-memory where a significant stress barrier is generated at the maximum of the cyclic shear strain.
Abstract: Materials such as rubber tend to soften when cyclically deformed. Here, however, the authors find that bundled actin networks can show cyclic hardening and retain a memory of the maximum strain they have been subjected to.

Journal ArticleDOI
TL;DR: In this article, the deformation and plastic collapse mechanisms of closed-cell Al foams under uniaxial compressive loading were analyzed with the method of finite elements and experimental measurements.

Journal ArticleDOI
TL;DR: In this article, a series of uni-axial tensile tests were carried out under various low temperatures and strain-rate ranges for AISI 300 austenitic stainless steel.

Journal ArticleDOI
TL;DR: In this paper, microstructural changes and cyclic deformation characteristics of friction-stir-welded 7075 Al alloy were evaluated and two low-hardness zones (LHZs) between the TMAZ and the heat-affected zone (HAZ) were observed, with the width decreasing with increasing welding speed.
Abstract: Microstructural changes and cyclic deformation characteristics of friction-stir-welded 7075 Al alloy were evaluated. Friction stir welding (FSW) resulted in significant grain refinement and dissolution of η′ (Mg(Zn,Al,Cu)2) precipitates in the nugget zone (NZ), but Mg3Cr2Al18 dispersoids remained nearly unchanged. In the thermomechanically affected zone (TMAZ), a high density of dislocations was observed and some dislocations were pinned, exhibiting a characteristic Orowan mechanism of dislocation bowing. Two low-hardness zones (LHZs) between the TMAZ and the heat-affected zone (HAZ) were observed, with the width decreasing with increasing welding speed. Cyclic hardening and fatigue life increased with increasing welding speed from 100 to 400 mm/min, but were only weakly dependent on the rotational rate between 800 and 1200 rpm. The cyclic hardening of the friction-stir-welded joints exhibiting a two-stage character was significantly stronger than that of the base metal (BM) and the energy dissipated per cycle decreased with decreasing strain amplitude and increasing number of cycles. Fatigue failure occurred in the LHZs at a lower welding speed and in the NZ at a higher welding speed. Fatigue cracks initiated from the specimen surface or near-surface defects in the friction-stir-welded joints, and the initiation site exhibited characteristic intergranular cracking. Crack propagation was characterized by typical fatigue striations along with secondary cracks.

Journal ArticleDOI
TL;DR: In this paper, a correlation between microstructural observations by various complementary techniques, which have been implemented within the PERFECT project, and the hardening measured by tensile tests of reactor pressure vessel steel and model alloys after irradiation to a dose of ∼7.5 n cm−2.

Journal ArticleDOI
TL;DR: In this paper, double-sided arc welded and friction stir welded (FSWed) alloy sheet were studied at different strain rates. And the authors evaluated the strain-hardening exponents using the Hollomon relationship, the Ludwik equation and a modified equation.
Abstract: Microstructures, tensile properties and work hardening behavior of double-sided arc welded (DSAWed) and friction stir welded (FSWed) AZ31B-H24 magnesium alloy sheet were studied at different strain rates. While the yield strength was higher, both the ultimate tensile strength and ductility were lower in the FSWed samples than in the DSAWed samples due to welding defects present at the bottom surface in the FSWed samples. Strain-hardening exponents were evaluated using the Hollomon relationship, the Ludwik equation and a modified equation. After welding, the strain-hardening exponents were nearly twice that of the base metal. The DSAWed samples exhibited stronger strain-hardening capacity due to the larger grain size coupled with the divorced eutectic structure containing -Mg17Al12 particles in the fusion zone, compared to the FSWed samples and base metal. Kocks-Mecking type plots were used to show strain-hardening stages. Stage III hardening occurred after yielding in both the base metal and the welded samples. At lower strains a higher strain-hardening rate was observed in the base metal, but it decreased rapidly with increasing net flow stress. At higher strains the strain-hardening rate of the welded samples became higher, because the recrystallized grains in the FSWed and the larger re-solidified grains coupled with particles in the DSAWed provided more space to accommodate dislocation multiplication during plastic deformation. The strain-rate sensitivity evaluated via Lindholm's approach was observed to be higher in the base metal than in the welded samples. © 2010 Elsevier B.V. All rights reserved.

Journal ArticleDOI
TL;DR: In this article, the low temperature embrittlement behavior of duplex stainless steel 2205 was investigated on the basis of changes in mechanical and electrochemical properties after aging for 5000h at 335, 365 and 400°C.
Abstract: The low temperature embrittlement behavior of duplex stainless steel 2205 was investigated on the basis of changes in mechanical and electrochemical properties after aging for 5000 h at 335, 365 and 400 °C. Aging leads to increase in the hardness of δ-ferrite phase. The ferrite hardening was very rapid in the initial stages of aging; thereafter the hardness increase was more gradual at all the aging temperatures. Charpy impact test of the aged samples showed drastic decrease in impact toughness. The value of Charpy impact energy saturated after aging to 5000 h at all the aging temperatures. The embrittlement in the material is known to be caused by spinodal decomposition reaction in which the δ-ferrite decomposes into iron-rich α and chromium-enriched α′. For the purpose of non-destructive evaluation of thermal aging embrittlement, double loop electrochemical potentiokinetic reactivation (DL-EPR) test and anodic polarizations in acetic acid and HCl solution were carried out. The peak current density during the anodic scan in DL-EPR test and the peak anodic current density for secondary passivation during polarization in acetic acid increased with increase in aging time. A good linear correlation was observed between the peak anodic current density for secondary passivation during polarization in acetic acid and the microhardness of δ-ferrite phase.

Journal ArticleDOI
TL;DR: In this article, an anisotropic material model based on non-associated flow rule and mixed isotropic-kinematic hardening was developed and implemented into a user-defined material (UMAT) subroutine for the commercial finite element code ABAQUS.

Journal ArticleDOI
TL;DR: In this paper, cyclic deformation and fatigue behaviors of stainless steel 304L and aluminum 7075-T6 were investigated, and the effects of loading sequence, mean strain or stress, and prestraining were investigated.
Abstract: This paper discusses cyclic deformation and fatigue behaviors of stainless steel 304L and aluminum 7075-T6. Effects of loading sequence, mean strain or stress, and prestraining were investigated. The behavior of aluminum is shown not to be affected by preloading, whereas the behavior of stainless steel is greatly influenced by prior loading. Mean stress relaxation in strain control and ratcheting in load control and their influence on fatigue life are discussed. Some unusual mean strain test results are presented for SS304L, where in spite of mean stress relaxation fatigue lives were significantly longer than fully-reversed tests. Prestraining indicated no effect on either deformation or fatigue behavior of aluminum, while it induced considerable hardening in SS304L and led to different results on fatigue life, depending on the test control mode. Possible mechanisms for secondary hardening observed in some tests, characterized by a continuous increase in the stress response and leading to runout fatigue life, are also discussed. The Smith-Watson-Topper parameter was shown to correlate most of the experimental data for both materials under different loading condition.

Journal ArticleDOI
TL;DR: In this paper, a new technique to perform in situ miniaturized bending fatigue experiments was applied to single crystal copper beams, where monotonic hardening and an increasing Bauschinger effect were observed with increasing normalized displacement.

Journal ArticleDOI
TL;DR: In this article, a method based on the strain energy density (SED) was used to represent cyclic hardening/softening behavior of the material in low cycle fatigue and in ratcheting.

Journal ArticleDOI
TL;DR: In this article, an aged Al-5Zn-1.6Mg alloy with fine precipitates was grain refined to ∼100nm grain size by means of confined channel die pressing.

Journal ArticleDOI
TL;DR: In this article, the effect of different thermo-mechanical treatments, including up to 10% cold work, on the hardness of the 2024 (Al-Cu-Mg) alloy was studied.

Journal ArticleDOI
TL;DR: In this article, the twin density in the plastic zone of compact tension (CT) specimens is very low, leading to the conclusion that the deformation mechanisms depend drastically on the loading conditions.
Abstract: The crack growth behavior of a high-manganese austenitic steel, which exhibits the twinning-induced plasticity (TWIP) effect, was investigated under positive stress ratios. An experimental study making use of miniature compact tension (CT) specimens and thorough microstructural analyses including transmission electron microscopy and fracture analyses demonstrated that the microstructural evolution in the plastic zone of the fatigued TWIP CT specimens is substantially different as compared to the monotonic plastic deformation case. Specifically, the twin density in the plastic zone of the CT specimens is very low, leading to the conclusion that the deformation mechanisms depend drastically on the loading conditions. The absence of twinning under cyclic loading in the plastic zone of the CT specimens indicates that even large accumulated plastic strains are not sufficient to cause substantial twinning in the TWIP steel. This lack of hardening preserves the ductile character of the TWIP steel in the plastic zone ahead of the crack tip and provides for a crack growth rate in the Paris regime lower than reported for other high strength steels.