Showing papers on "Hardening (metallurgy) published in 2017"
TL;DR: This study discovered that plastic deformation mechanism of extremely fine nanograined metals and their hardness are adjustable through tailoring grain boundary (GB) stability, which provides an alternative dimension, in addition to grain size, for producing novel nanograin metals with extraordinary properties.
Abstract: Conventional metals become harder with decreasing grain sizes, following the classical Hall-Petch relationship. However, this relationship fails and softening occurs at some grain sizes in the nanometer regime for some alloys. In this study, we discovered that plastic deformation mechanism of extremely fine nanograined metals and their hardness are adjustable through tailoring grain boundary (GB) stability. The electrodeposited nanograined nickel-molybdenum (Ni–Mo) samples become softened for grain sizes below 10 nanometers because of GB-mediated processes. With GB stabilization through relaxation and Mo segregation, ultrahigh hardness is achieved in the nanograined samples with a plastic deformation mechanism dominated by generation of extended partial dislocations. Grain boundary stability provides an alternative dimension, in addition to grain size, for producing novel nanograined metals with extraordinary properties.
524 citations
TL;DR: In this paper, a new cementitious material, ultra-high ductile cementitious composites (UHDCCs), is developed with the specially selected polyethylene (PE) fibers.
298 citations
14 Mar 2017-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the authors used nanoindentation to evaluate the elastic modulus and hardness properties of the Ti and Ti-TiB composite materials, and showed that the results showed that there is a high degree of consistency between the characterization using nanoinfentation and the wear evaluation from conventional wear tests.
Abstract: Ti and Ti-TiB composite materials were produced by selective laser melting (SLM). Ti showed an α΄ microstructure, whereas the Ti-TiB composite revealed a distribution of needle-like TiB particles across an α-Ti matrix. Hardness (H) and reduced elastic modulus (Er) were investigated by nanoindentation using loads of 2, 5 and 10 mN. The results showed higher H and Er values for the Ti-TiB than Ti due to the hardening and stiffening effects of the TiB reinforcements. On increasing the nanoindentation load, H and Er were decreased. Comparison of the nanoindentation results with those derived from conventional hardness and compression tests indicated that 5 mN is the most suitable nanoindentation load to assess the elastic modulus and hardness properties. The wear resistance of the samples was related to their corresponding H/Er and H3/Er2 ratios obtained by nanoindentation. These investigations showed that there is a high degree of consistency between the characterization using nanoindentation and the wear evaluation from conventional wear tests.
221 citations
17 Sep 2017-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, a detailed study sheds light on the origins of the observed high yield strength and good ductility of additively manufactured (AM) 316L steel, and the dominant twinning activity is attributed to Nitrogen gas used in 3D printing, leading to the disassociation of dislocations, promoting deformation twinning.
Abstract: Additively manufactured (AM) 316L steel exhibits extraordinary high yield strength, and surprisingly good ductility despite the high level of porosity in the material. This detailed study sheds light on the origins of the observed high yield strength and good ductility. The extremely fine cells which are formed because of rapid cooling and dense dislocations are responsible for the macroscopically high yield strength of the AM 316L (almost double of that seen in annealed 316L steel). Most interestingly, twinning is dominant in deformed samples of the AM316. It is believed that twinning-induced plasticity (TWIP) behaviour to be responsible for the excellent ductility of the steel despite the high level of porosity. The dominant twinning activity is attributed to Nitrogen gas used in 3D printing. Nitrogen can lower the stacking fault energy of the steel, leading to the disassociation of dislocations, promoting the deformation twinning. Twinning induces large plasticity during deformation that can compensate the negative effect of porosity in AM steel. However, twinning does not induce significant hardening because (1) the porosity causes a negative effect on hardening and (2) twinning spacing is still larger than extremely fine solidification cells.
206 citations
TL;DR: In this article, a dislocation density-based continuum plasticity model was proposed to investigate the strain hardening of a gradient interstitial-free steel by developing a dislocated density-and back stress model, in which the interaction of the component layers in the gradient structure was represented by incorporating geometrically necessary dislocations and back stress.
188 citations
TL;DR: It is proposed that the excellent strain hardening ability gives rise to remarkable resistance to shear localization, which makes this material an excellent candidate for penetration protection applications such as armors.
Abstract: The mechanical behavior of a single phase (fcc) Al0.3CoCrFeNi high-entropy alloy (HEA) was studied in the low and high strain-rate regimes. The combination of multiple strengthening mechanisms such as solid solution hardening, forest dislocation hardening, as well as mechanical twinning leads to a high work hardening rate, which is significantly larger than that for Al and is retained in the dynamic regime. The resistance to shear localization was studied by dynamically-loading hat-shaped specimens to induce forced shear localization. However, no adiabatic shear band could be observed. It is therefore proposed that the excellent strain hardening ability gives rise to remarkable resistance to shear localization, which makes this material an excellent candidate for penetration protection applications such as armors.
154 citations
TL;DR: In this paper, a detailed investigation into the anisotropic strain hardening, tension/compression yield asymmetry, and evolution of crystallographic texture of rolled WE43 rare earth magnesium alloy during quasi-static tension and compression at room temperature is presented.
136 citations
TL;DR: An elasto-plastic polycrystal plasticity model is developed and applied to an Inconel 718 (IN718) superalloy that was produced by additive manufacturing as mentioned in this paper.
131 citations
TL;DR: In this paper, the microstructure and tensile properties of the Inconel 718 alloy were studied in the as-printed and different heat treat conditions, and the SLM as-print microstructures exhi...
Abstract: The microstructure and tensile properties of selective laser melted (SLM) Inconel 718 alloy were studied in the as-printed and different heat treat conditions. The SLM as-print microstructures exhi...
129 citations
TL;DR: In this article, the influence of heat treatment on the anisotropic plastic deformation behaviors of 6016-O and 6016 T4 aluminum alloy sheets was investigated and an appropriate yield function for each material was determined and employed in the finite element analysis of the hole expansion forming process.
125 citations
TL;DR: In this article, a deformation-based design approach called the continuous strength method (CSM) has been proposed for the design of stocky cross-sections, which relates the strength of a cross-section to its deformation capacity and employs a bi-linear (elastic, linear hardening) material model to account for strain hardening.
TL;DR: In this article, the effects of LSP on the microstructure, residual stress, hardness, strength, and fatigue life of ATI 718 Plus (718Plus) alloy was investigated and the results are reported.
TL;DR: In this paper, two strategies and technologies to improve the strain controlled low-cycle fatigue (LCF) performance of Fe-Mn-C twinning induced plasticity (TWIP) steel were introduced.
TL;DR: In this article, the compressive behavior of Ti-6Al-4V lattice structures with rhombic dodecahedron unit cells is investigated at four different strain rates, and the peak stress exhibits a certain dependence on the loading rate for the structures with smaller unit cells.
TL;DR: In this paper, a temperature-dependent micromechanical behavior of medium-Mn transformation-inducedplasticity (TRIP) steel with a nominal chemical composition of Fe-0.1C-10Mn-2Al (mass%) fabricated by intercritical annealing 650°C for 1 1/h after cold-rolling was investigated using in situ high-energy X-ray diffraction (HE-XRD) with uniaxial tensile tests at temperatures of 100, 25 and 50°C.
TL;DR: Graphene oxide (GO) powder was dispersed in an AlMg5 matrix using high energy ball milling and the obtained blend was then completely densified by hot pressing as mentioned in this paper.
TL;DR: In this paper, a simple coupling of quadratic and non-quadratic yield functions with a non-associated flow rule is proposed to describe the evolution of yield surface (or anisotropic hardening).
TL;DR: In this paper, the deformation analysis confirmed complete SME recovery of approximately −2.0% macro-scale and −4.5% micro-scale/concentrated strains.
TL;DR: In this paper, the work hardening behavior of Mg-Y binary alloys has been studied under uniaxial tension and compression at 4,K, 78,K and 298,K.
TL;DR: In this paper, a mesoscopic solid-solution model was proposed to predict the energy barriers of dislocation motion caused by solute-dislocation interactions using a first-principles approach with flexible boundary conditions.
TL;DR: In this paper, a compelling finite element framework to model hydrogen assisted fatigue by means of a hydrogen-and cycle-dependent cohesive zone formulation is presented, where the role of yield strength, work hardening, and constraint conditions in enhancing crack growth rates as a function of the loading frequency is thoroughly investigated.
TL;DR: In this article, the authors used a hemispherical dome test with specimens of different widths to determine the forming limit diagram (FLD) for Ti-6Al-4 V alloy at 400°C.
Abstract: Forming limit diagram (FLD) is an important performance index to describe the maximum limit of principal strains that can be sustained by sheet metals till to the onset of localized necking. It is useful tool to access the forming severity of a drawing or stamping processes. In the present work, FLD has been determined experimentally for Ti-6Al-4 V alloy at 400 °C by conducting a hemispherical dome test with specimens of different widths. Additionally, theoretical FLDs have been determined using Marciniak Kuczynski (M-K) model. Various yield criteria namely: Von Mises, Hill 1948, Hill 1993 and Cazacu Barlat in combination with different hardening models viz., Hollomon power law (HPL), Johnson-Cook (JC), modified Johnson-Cook (m-JC), modified Arrhenius (m-Arr.), modified Zerilli–Armstrong (m-ZA) have been used in M-K analysis for theoretical FLD prediction. The material properties required for determination of yield criteria and hardening models constants have been calculated using uniaxial tensile tests. The predicted theoretical FLDs results are compared with experimental FLD. It can be observed that influence of yield criterion in M-K analysis for theoretical FLD prediction is predominant than the hardening model. Based on the results; it is observed that the theoretical FLD using Cazacu Barlat and Hill 1993 yield criteria with m-Arr. hardening model has a very good agreement with experimental FLD.
TL;DR: In this article, the authors evaluated the stress-strain relationship between Al and Si constituents in AlSi10Mg alloy produced by selective laser melting (SLM) under uniaxial tension at room temperature.
TL;DR: In this article, the authors numerically studied the role of exhaustion of twinning in magnesium alloys under twinning dominated conditions, based on the large strain elastic visco-plastic self-consistent model.
TL;DR: In this article, a carbide-containing FeCoCrNiMn alloy was prepared by arc melting, and its microstructure and mechanical properties were further tuned by cold rolling with subsequent annealing treatment.
Abstract: Previous studies have reported that high carbon contents in FeCoCrNiMn high-entropy alloys lead to carbides precipitating from the alloys. Typically, carbides are used to improve the strength of alloys but also lead to decreased ductility. However, the strength and ductility of alloys can be improved when carbides shape, size and distribution are carefully controlled. Therefore, a carbide-containing FeCoCrNiMn alloy with 2 at.-% carbon was prepared by arc melting, and its microstructure and mechanical properties were further tuned by cold rolling with subsequent annealing treatment. The yield strength and uniform elongation of the resultant alloy were excellent, reaching 581 MPa and 25%, respectively, due to the additive combination of various strengthening mechanisms, such as solid-solution hardening, grain-boundary hardening and precipitation hardening.
TL;DR: In this article, the effect of laser peening without coating on the hardness of an aluminium alloy was investigated and the Vickers micro-hardness test was used to study the hardness with different wavelengths and laser intensities.
TL;DR: In this paper, the deformation evolution across several crystal orientations for the equiatomic FeNiCoCrMn high entropy alloy at room temperature (RT) and 77 K was explored.
TL;DR: In this article, a detailed analysis of the plastic deformation characteristics was performed for an extruded ZK60 magnesium alloy under uniaxial cyclic loading along the extrusion direction.
TL;DR: In this article, a mechanistic model was developed for modeling the depth-dependent hardness in ion irradiated metallic materials, which is capable of capturing the indentation size effect, ion irradiation induced damage gradient effect, and effect of unirradiated region acting as a soft substrate.
TL;DR: In this paper, the authors investigated the use of LSP to improve the fatigue life of ATI 718 Plus (718Plus) at high temperature of 650°C and found that LSP led to severe surface plastic deformation, which led to a high magnitude of surface compressive residual stresses and changes in the near-surface microstructure which caused high surface hardening.