Showing papers on "Hardening (metallurgy) published in 2011"
TL;DR: In this article, the authors studied the kinetics of the substructure evolution and its correspondence to the strain hardening evolution of an Fe-22 wt.% Mn-0.6 wt% C TWIP steel during tensile deformation by means of electron channeling contrast imaging (ECCI) combined with electron backscatter diffraction (EBSD).
677 citations
TL;DR: In this paper, an approach is proposed for the description of the plastic behavior of materials subjected to multiple or continuous strain path changes, which is not formulated with a kinematic hardening rule.
330 citations
TL;DR: In this paper, it was shown that the properties of the ferrite phase change with distance from the martensite grains, leading to the idea that local hardening is caused by geometrically necessary dislocations.
326 citations
TL;DR: In this paper, a steel wire with a structural scale in the nanometer range and a flow stress of about 3.5 GPa was drawn up to a strain of 3.7.
268 citations
TL;DR: In this article, the effects of tempering temperature and time on the microstructure, mechanical and corrosion properties of AISI420 have been studied and the experimental results showed that the austeitizing temperature significantly affects mechanical properties.
246 citations
TL;DR: In this paper, the microstructure, texture, ductility, and stretch formability of rolled Mg-2%Gd-1%Zn and Mg -3% Gd- 1% Zn sheets were investigated.
220 citations
TL;DR: In this article, the authors investigated the irradiation hardening of Fe-based model ferritic alloys after Fe-ion irradiation experiments in order to deduce mechanistically based nominal hardness from the nano-indentation tests on the ion-irradiated surface.
190 citations
25 Mar 2011-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, a 3D representation of dislocation structure evolution during cyclic loading is proposed on the basis of the microstructural observations, which provides a deeper insight into the development of dislocated structures in AISI 316L during low cycle fatigue loading at room temperature.
Abstract: The cyclic deformation response of an austenitic stainless steel is characterised in terms of its cyclic peak tensile stress properties by three stages of behaviour: a hardening stage followed by a softening stage, and finally a stable stress response stage. A series of tests have been performed and interrupted at selected numbers of cycles in the different stages of mechanical response. At each interruption point, specimens have been examined by transmission electron microscopy (TEM) with different beam directions by means of the tilting function in order to investigate the formation and the development of dislocation structures from the as-received condition until the end of fatigue life. A new 3D representation of dislocation structure evolution during cyclic loading is proposed on the basis of the microstructural observations. The 3D representation provides a deeper insight into the development of dislocation structures in AISI 316L during low cycle fatigue loading at room temperature. By investigating the dislocation evolution, the study shows that the hardening response is mainly associated with an increase of total dislocation density, whereas the softening stage is a result of the formation of dislocation-free regions. Further development of the dislocation structure into a cellular structure is responsible for the stable stress response stage.
164 citations
TL;DR: In this paper, a model describing layer-thickness-dependent radiation hardening in multilayers was developed by extending the Friedel model to take into account the layer thickness and the He bubble spacing.
160 citations
TL;DR: In this paper, the authors investigate the mechanical properties of multiple slip oriented single crystal Cu(1.0) compression samples to shed light on size-dependent yield and hardening behavior at small-scales.
156 citations
TL;DR: In this article, a set of mechanism-based unified creep ageing constitutive equations has been formulated, which models creep induced evolution of precipitates, dislocation hardening, solid solution hardening and age-precipitation hardening.
TL;DR: In this paper, an alternative method to identify the post-necking hardening behavior of sheet metal without using a finite element model is presented, where the key point is the minimization of the discrepancy between the internal and external work in the necking zone during a tensile test.
TL;DR: In this paper, the cyclic deformation of extruded AZ61A magnesium alloy was investigated under fully reversed strain-controlled tension-compression, torsion, and combined axial-torsion in ambient air.
TL;DR: In this article, the effect of ageing on mechanical properties and microstructural characteristics of a precipitation hardenable Al 7075 alloy subjected to rolling at liquid nitrogen temperature and room temperature is investigated.
TL;DR: In this paper, the effect of the pseudoelastic strain resulting from elastic twinning was investigated in cast specimens of Mg and of several Mg-Zn binary alloys with a wide range of grain sizes.
Abstract: Cast specimens of Mg and of several Mg-Zn binary alloys with a wide range of grain sizes were deformed in tension and compression. The k values calculated from the Hall–Petch (H-P) plots of the tensile 0.2 pct proof stress increased with the Zn content, from 0.24 MPa m1/2 for pure Mg to ~0.66 MPa m1/2 for the 2.3 at. pct Zn alloy; k values measured from compression tests were larger, typically by 0.05 MPa m1/2. When the strength measurements were corrected for the pseudoelastic strain resulting from elastic twinning, the k values generally increased, and the difference between tension and compression was eliminated. This showed that the larger k values obtained in compression using uncorrected data were an artifact of the pseudoelastic effect. The apparent friction stress varied between about 14 MPa for pure Mg to very low or negative values for the most dilute alloy, increasing again to about 8 MPa for the most concentrated alloy. The use of strength data corrected for pseudoelasticity effects is necessary for a consistent analysis of the grain size hardening.
TL;DR: In this article, an extensive parametric study is performed on two-dimensional (2D) axisymmetric finite element (FE) unit cell calculations, using a Kocks-Mecking type hardening law.
TL;DR: In this article, the mechanical stability of Pb-free SnAgCu solder connections is studied in comparison to conventional eutectic SnPb. The strength and ductility of the Pbfree joints depend significantly on Ag content.
25 Oct 2011-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the microstructure and mechanical properties of a newly developed Al-7%Si-1%Cu-0.5%Mg cast alloy with further additions of Ti, Zr and V were evaluated.
Abstract: The development of aluminum alloys for automotive powertrain applications is in high demand due to the required weight reduction and fuel efficiency. The aim of this study was to evaluate the microstructure and mechanical properties of a newly developed Al–7%Si–1%Cu–0.5%Mg cast alloy with further additions of Ti, Zr and V. The microstructure of the alloys consisted of Al dendrites surrounded by Al–Si eutectic structures with Mg/Cu/Fe-containing Si particles, and contained nano-sized trialuminide precipitates in the Ti/Zr/V added alloys. The alloys had a significantly (60–87%) higher yield strength but lower ductility than A356-T6 and 319-T6 alloys. With the addition of Ti/Zr/V both monotonic and cyclic yield strengths increased, but ductility and hardening capacity decreased due to reduced dislocation storage capacity caused by stronger interactions between dislocations and trialuminide precipitates. The Zr/V-modified alloy had a longer fatigue life, and all the alloys exhibited cyclic stabilization at low strain amplitudes and cyclic hardening at higher strain amplitudes. With increasing strain amplitude, the extent of cyclic hardening increased. Both cyclic yield strength and cyclic strain hardening exponent were higher than the corresponding monotonic yield strength and strain hardening exponent, indicating that a stronger cyclic hardening ability of the alloys developed. Fatigue cracks were observed to initiate at near-surface defects, and crack propagation was mainly characterized by the formation of fatigue striations together with secondary cracks.
TL;DR: In this paper, the influence of temperature on irradiation hardening and microstructure development in irradiated tungsten-rhenium (W-Re) alloys was investigated.
Abstract: The aim of this work is to investigate the influence of neutron irradiation condition, especially temperature, on irradiation hardening and microstructure development in irradiated tungsten-rhenium (W-Re) alloys. Neutron irradiations were carried out in JOYO at the range of 400 to 750 � C, up to 1.54 dpa. Micro Vickers hardness tests and micro structural observations using a TEM were performed. Irradiation hardening of WRe alloys irradiated at 538 � C were clearly larger than those irradiated at other temperatures. Fine voids and fine needle- or plate-like precipitates were observed in pure W and W-Re alloys irradiated at 538 � C, respectively, with high number density. The fine complex microstructure seems to be the cause of the characteristic irradiation hardening. [doi:10.2320/matertrans.MBW201025]
TL;DR: In this paper, different cyclic plastic deformation responses of piping materials (SA333 C-Mn steel and 304LN stainless steel) are experimentally explored, and effects of stress amplitude and mean stress on the ratcheting behaviors are analyzed.
TL;DR: In this article, the performance of extruded ZK60 Mg alloy under different heat treatments (T4, T5 and T6) was studied using uniaxial tensile tests at room temperature.
TL;DR: In this paper, the effects of irradiation temperature, damage level and Re content on hardening and electrical resistivity were discussed, and the property change mechanism was discussed considering the irradiated microstructure and solute elements.
TL;DR: In this article, reduced activation Ferritic/Martensitic (RAFM) steels were studied after irradiation in BOR-60 reactor to a neutron displacement damage of 70-dpa at 330-340°C.
TL;DR: In this paper, the Fatemi-Socie critical plane approach was used to evaluate axial-torsion strain paths with random and incremental changes in straining direction, and fatigue life and available cycle counting methodologies were examined under discriminating axial torsion straining paths with different axial to shear strain ratios within an equivalent strain circle.
TL;DR: In this paper, the authors developed the ultrafine-grained 2024 aluminum alloy (A2024) and A2024 matrix composites containing carbon nanotubes (CNTs) and employed three strengthening strategies of grain boundary hardening, age hardening and hardening by CNTs.
Abstract: The ultrafine-grained 2024 aluminum alloy (A2024) and A2024 matrix composites containing carbon nanotubes (CNTs) are developed. Three strengthening strategies of grain boundary hardening, age hardening and hardening by CNTs are employed. First, grain size of A2024 is effectively reduced using a ball-milling technique and A2024 with a grain size of 100 nm exhibits a yield stress of ∼560 MPa, exhibiting a well agreement with the Hall–Petch relation. CNTs also have a great effect for strengthening. The A2024 matrix composite containing 3 vol.% CNTs shows a yield stress of ∼780 MPa with 2% tensile elongation to failure. Hardness is further increased after aging. The nanostructured composite shows its peak hardness after 4 h of aging because the refined grain boundaries and CNTs act as a pathway for diffusion of atoms with stimulating the aging process. The composite in the present study has great potential for application as structural materials in industry.
TL;DR: In this article, the authors compared experimental measurements and simulation results for the evolution of plastic deformation and hardening in micropillars and employed physics-based constitutive rules for an adequate representation of hardening.
01 Jan 2011
TL;DR: The RHT concrete model is implemented in LS-DYNA and incorporates features that are necessary for a corr ect dynamic strength description of concrete at imp act relevant strain rates and pressures as discussed by the authors.
Abstract: The RHT concrete model is implemented in LS-DYNA. It is a macro-scale material model that incorporates features that are necessary for a corr ect dynamic strength description of concrete at imp act relevant strain rates and pressures. The shear stre ngth of the model is described by means of three li mit surfaces; the inelastic yield surface, the failure surface and the residual surface, all dependent on the pressure. The post-yield and post-failure behaviors are characterized by strain hardening and damage, respectively, and strain rate effects is an importa nt ingredient in this context. Furthermore, the pre ssure is governed by the Mie-Gruneisen equation of state tog ether with a p-α model to describe the pore compaction hardening effects and thus give a realis tic response in the high pressure regime. Validatio ns have been performed on smaller test examples and a contact detonation application is presented to illu strate the performance of the proposed model.
15 Nov 2011-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the mechanical properties of AZ31 magnesium alloys with different grain sizes, basal texture intensities and twinning conditions were investigated at room temperature, and it was found that the rolled sheets show good ductility when grain size is around 15μm.
Abstract: Rolled sheets with various microstructures and (0 0 0 2) pole intensities have been obtained successfully using conventional flat rolling (CFR), differential speed rolling (DSR) and heat treatment methods. The mechanical properties of AZ31 magnesium alloys with different grain sizes, basal texture intensities and twinning conditions were investigated at room temperature. It was found that the rolled sheets show good ductility when grain size is around 15 μm. Finer grains and random (0 0 0 2) basal intensity are hardly achieved simultaneously using both DSR-RS and CFR-AR processing methods in current study. In the determination of the rolling processing, it is important to consider preferred grain refinement or lowered basal texture intensity. Moreover, the influences of grain size, basal texture intensity and twinning conditions on work-hardening rate were examined as well. As grain size decreases, extrapolated work-hardening rate decreases; while basal texture intensity has little effect on it. On the other hand, twinning plays a vital role in decreasing work-hardening in plastic flow stage; while twin boundaries increase the work-hardening rate in easy glide stage and linear hardening stage. However, they drop faster than un-twinned samples in stage III when the true strain is higher than 0.06.
TL;DR: In this article, the authors examined two distinct modes of behavior that reflect the dominant physical mechanisms of plastic deformation at small scales and found that the residence lifetimes of internal dislocation sources formed by cross-slip decrease as the system size decreases.