GPa Tensile Strength Research Articles

FeNiCoAlTaB superelastic and shape-memory wires with oligocrystalline grain structure

FeNiCoAlTaB shape-memory alloys are desirable alternatives to other smart metallic materials owing to their low base metal and processing costs. These alloys, however, require strong texture via thermomechanical treatments or directional solidification to obtain good functional properties. Here, we demonstrate the fabrication of FeNiCoAlTaB shape-memory wires by a rapid, continuous wire-casting process. These untextured wires exhibit 7% superelastic strains and 1.2 GPa tensile strength after training, and show good cyclability and low stress hysteresis at room temperature. These properties far surpass previous reports in untextured polycrystalline ferrous alloys, an improvement which we attribute to their unique oligocrystalline grain structure.

Design of a high strength, high ductility 12 wt% Mn medium manganese steel with hierarchical deformation behaviour

A novel medium Mn steel of composition Fe-12Mn-4.8Al-2Si-0.32C-0.3V was manufactured with 1.09 GPa yield strength, 1.26 GPa tensile strength and 54% elongation. The thermomechanical process route was designed to be industrially translatable and consists of hot and then warm rolling followed by a 30 min intercritical anneal. The resulting microstructure comprised of coarse elongated austenite grains in the rolling direction surrounded by necklace layers of fine austenite and ferrite grains. The tensile behaviour was investigated by in-situ neutron diffraction and the evolution of microstructure studied with Electron Backscattered Diffraction (EBSD). It was found that the coarse austenite grains contributed to the first stage of strain hardening by transforming into martensite and the fine austenite necklace grains contributed to the second stage of strain hardening by a mixture of twinning and transformation induced plasticity (TWIP and TRIP) mechanisms. This hierarchical deformation behaviour contributed to the exceptional ductility of this steel.

Mechanical properties of Invar 36 alloy additively manufactured by selective laser melting

Invar 36 alloy is widely used in aerospace engineering, owing to its extremely low coefficient of thermal expansion. This work aims to explore the underlying influence of process parameters on the microstructures and mechanical properties of Invar 36 additively manufactured by selective laser melting (SLM) with island scanning strategy. A full factorial design for a wide range of SLM process parameter sequence was established. Density and the mechanical properties including hardness, tensile strength as well as microstructures, fractography were characterized. The results confirm that the increment of exposure time and the reduction of point distance remarkably induce stable melting and achieve superior density and hardness. The laser energy density shows a pronounced effect on the microstructures, as extremely low laser energy density induces considerable lack-of fusion pores, unmelted powder particles and blurry boundaries of islands. While, very high laser energy density induces a few keyhole pores, and makes the laser scanning tracks and island boundaries transfer to be irregular. The optimal laser energy density is recommended to be 99.2 J/mm3, and the as-fabricated Invar 36 shows the relative density of 99.5%, Vickers hardness of 1.8 GPa and ultimate tensile strength of 480 MPa those are very comparable to conventionally fabricated one. The testing temperatures of 200 °C and 600 °C induce the coarsening of γ phase, and result in a significant degeneration of tensile properties. The correlations between the SLM process and mechanical properties provide experimental basis of the additive manufacturing Invar 36 alloy.

Process control maps to design an ultra-high strength-ductile steel

ABSTRACTSteel with 2.4–2.5 GPa tensile strength and elongation to fracture of 4.8–5.7%, is produced by designing a novel heat treatment identical to quenching and tempering, in less than a few minutes. Since addition of Si to Fe–Mn steel promotes the austenite stabilisation by carbon enrichment, the elongation to fracture of 0.6C–1.6Si–1.2Mn (wt-%) steel treated by different quenching and partitioning (Q&P) routes is improved. Results demonstrated by process control maps give a good overview of the final microconstituents. By using higher partitioning temperatures, the tempering of martensite, stabilisation of austenite and improvement of the mechanical properties, could effectively be accelerated. This approach results in significant time and cost reduction which makes this heat treatment attractive for industries.

CRISPR/Cas9 Initiated Transgenic Silkworms as a Natural Spinner of Spider Silk.

Using transgenic silkworms with their natural spinning apparatus has proven to be a promising way to spin spider silk-like fibers. The challenges are incorporating native-size spider silk proteins and achieving an inheritable transgenic silkworm strain. In this study, a CRISPR/Cas9 initiated fixed-point strategy was used to successfully incorporate spider silk protein genes into the Bombyx mori genome. Native-size spider silk genes (up to 10 kb) were inserted into an intron of the fibroin heavy or light chain (FibH or FibL) ensuring that any sequence changes induced by the CRISPR/Cas9 would not impact protein production. The resulting fibers are as strong as native spider silks (1.2 GPa tensile strength). The transgenic silkworms have been tracked for several generations with normal inheritance of the transgenes. This strategy demonstrates the feasibility of using silkworms as a natural spider silk spinner for industrial production of high-performance fibers.

Triumfetta cordifolia: A Valuable (African) Source for Biocomposites

The tradition of using naturally occurring plant fibers is still alive in Africa. In the Uige province of northern Angola, bast fibers from Triumfetta cordifolia serve as the basis for everyday objects, such as baskets, mats, fishing nets, and traditional clothing. The fibers exhibit a Young’s modulus of 53.4 GPa and average tensile strength of 916.3 MPa, which are comparable to those of commercial kenaf fibers. These values indicate a high potential for use as a reinforcement in biocomposites. Based on this promising mechanical and physical profile of individual fibers, different biocomposites were produced with polylactide (PLA) as a matrix. The obtained composites were analyzed mechanically, physically, and visually. Unidirectionally arranged PLA/33% T. cordifolia composites with continuous fibers showed the highest Young’s modulus (10.79 GPa ± 1.52 GPa) and tensile strength (79.37 MPa ± 14.01 MPa). These composites were comparable to those of PLA/30% hemp composites (10.9 GPa and 82.9 MPa, respectively) and therefore have economic potential.

A low-alloy high-carbon martensite steel with 2.6 GPa tensile strength and good ductility

A low-alloy and high-carbon martensite steel (0.66% C) with ultrafine grains is produced by combination of Tempforming (tempering and deforming of a quenched steel) and reheating followed by water quenching and low temperature tempering. The size of prior-austenite grains of the steel is reduced to 2.4 μm through this new technique, and its ultimate tensile strength of 2.6 GPa and elongation of 7% are obtained, which is the highest strength in low alloy high strength steels. The microstructure of the high carbon martensite consists of high density dislocations, undissolved spherical carbides, and dispersed nano-scale Fe3C and Fe5C2 phases precipitated at interior of martensitic after tempering. The strengthening mechanisms of the ultrafine grain martensitic steel are mainly dislocation strengthening and precipitation strengthening and also fine grain strengthening. The tensile strength and ductility of the steel are superior to that of existing maraging steels, such as C350, the highest strength in commercialized level, in which more than 20% precious alloy elements such as Co, Mo, Ni, and Ti are contained, and the cost of our materials is only about 1/50 of the C350. All above advantages are desirable for broad industrial applications at an economic cost.

Rapid and Continuous Preparation of Polyacrylonitrile-Based Carbon Fibers with Electron-Beam Irradiation Pretreatment.

Thermal stabilization is a critical, yet time- and energy-consuming process during the preparation of PAN-based carbon fibers. In this work, automobile-grade carbon fibers with a 2.85 GPa tensile strength and a 203 GPa modulus are continuously produced with electron-beam (e-beam) irradiation pretreatment and 24 min thermal stabilization. Thermal and structural analyses reveal that e-beam irradiation can lower the onset temperature of the cyclization reaction and mitigate the heat release. Meanwhile, during the process of stabilization, e-beam irradiation can facilitate the evolution of both the chemical structure and the crystalline structure of polyacrylonitrile (PAN) fibers. Comparing to the industrial production of carbon fiber with a 40 min stabilization time, e-beam irradiated PAN fibers can achieve the same degree of stabilization with a 40% time savings.

Experimental and multi-scale numerical evaluations for effective mechanical properties of 2-D Cf/Mg composites

2-D Cf/Mg composites consisting of AZ91D magnesium alloy and carbon non-woven fabrics are prepared by using the LSEVI process and their mechanical properties are experimentally tested. The experimental results show that the 2-D Cf/Mg composites have the better mechanical properties: elastic modulus of 71.0 GPa and ultimate tensile strength of 366.0 MPa, compared to AZ91D magnesium alloy matrix with the elastic modulus of 45.0 GPa and ultimate tensile strength of 250.0 MPa. The effective elastic properties of the 2-D Cf/Mg composites are numerically predicted by using a multi-scale homogenization method: the RVE based FE homogenization method at the macro-scale coupling the D-I mean-field homogenization model at the micro-scale. The agreement between the results of the experimental tests and the multi-scale homogenization method illustrates the validation of the multi-scale homogenization method to evaluate the effective mechanical properties of the 2-D Cf/Mg composites. For improving the computational efficiency, at the macro-scale the laminated composites theory is coupled with the RVE based FE homogenization method to predict the effective mechanical properties of the 2-D Cf/Mg composites.

Incorporation of AWS 316L wire nanostructured with nickel-carbon nanotube by arc welding

Carbon nanotubes have certain properties, such as 150 GPa tensile strength, a 1000 GPa shear modulus, an electrical conductivity of 60 S/m, and a high thermal conductivity of 2500 W/mk, that make them an optimum metallic matrix composite reinforcement. Otherwise, arc welding is a common industrial process that joins almost all metals. However, there are hardly any studies involving the addition of carbon nanotubes in stainless steel so far. In this research, we show the incorporation of an AWS 316L nanostructured wire with nickel-carbon nanotubes in austenitic stainless steel via pulsed gas tungsten arc welding, which formed nanocomposites with 0.75 and 1.5 wt% carbon nanotube contents in the wire. The characterization was performed by scanning electronic microscope, Raman spectroscopy, and X-ray diffraction. The Vickers microhardness test was used to analyze the mechanical properties. The nanostructure composite had microstructure modification, and superficial microhardness improved in 35% for 0.75 wt% carbon nanotube.

High‐Modulus Low‐Cost Carbon Fibers from Polyethylene Enabled by Boron Catalyzed Graphitization

Currently, carbon fibers (CFs) from the solution spinning, air oxidation, and carbonization of polyacrylonitrile impose a lower price limit of ≈$10 per lb, limiting the growth in industrial and automotive markets. Polyethylene is a promising precursor to enable a high-volume industrial grade CF as it is low cost, melt spinnable and has high carbon content. However, sulfonated polyethylene (SPE)-derived CFs have thus far fallen short of the 200 GPa tensile modulus threshold for industrial applicability. Here, a graphitization process is presented catalyzed by the addition of boron that produces carbon fiber with >400 GPa tensile modulus at 2400 °C. Wide angle X-ray diffraction collected during carbonization reveals that the presence of boron reduces the onset of graphitization by nearly 400 °C, beginning around 1200 °C. The B-doped SPE-CFs herein attain 200 GPa tensile modulus and 2.4 GPa tensile strength at the practical carbonization temperature of 1800 °C.

Ultra high stiffness and thermal conductivity of graphene like C3N

Recently, single crystalline carbon nitride 2D material with a C3N stoichiometry has been synthesized. In this investigation, we explored the mechanical response and thermal transport along pristine, free-standing and single-layer C3N. To this aim, we conducted extensive first-principles density functional theory (DFT) calculations as well as molecular dynamics (MD) simulations. DFT results reveal that C3N nanofilms can yield remarkably high elastic modulus of 341 GPa nm and tensile strength of 35 GPa nm, very close to those of defect-free graphene. Classical MD simulations performed at a low temperature, predict accurately the elastic modulus of 2D C3N with less than 3% difference with the first-principles estimation. The deformation process of C3N nanosheets was studied both by the DFT and MD simulations. Ab initio molecular dynamics simulations show that single-layer C3N can withstand high temperatures like 4000 K. Remarkably, the phononic thermal conductivity of free-standing C3N was predicted to be as high as 815 ± 20 W/mK. Our atomistic modelling results reveal ultra high stiffness and thermal conductivity of C3N nanomembranes and therefore propose them as promising candidates for new application such as the thermal management in nanoelectronics or simultaneously reinforcing the thermal and mechanical properties of polymeric materials.

Mechanical properties of polyimide/multi-walled carbon nanotube composite fibers

A series of polyimide (PI)/multi-walled carbon nanotube (MWCNT) composite fibers were prepared by copolymerizing a mixture of monomers and carboxylic-functionalized MWCNTs, followed by dry-jet wet spinning, thermal imidization, and hot-drawing process. The content of the carboxylic groups of MWCNTs significantly increased when treated with mixed acid, whereas their length decreased with treatment time. Both the carboxylic content and length of MWCNTs influenced the mechanical properties of the composite fibers. Fiber added with 0.1 wt% MWCNTs treated for 4 h exhibited the best mechanical properties, i.e., 1.4 GPa tensile strength and 14.30% elongation at break, which were 51% and 32% higher than those of pure PI fibers, respectively. These results indicated that a suitable MWCNT content strengthened and toughened the resultant PI composite fibers, simultaneously. Moreover, raising draw ratio resulted in the increase of tensile strength and tensile modulus of the composite fibers.

Formabilities of C-Si-Al-Mn Transformation-Induced Plasticity-Aided Martensitic Sheet Steel

The substitution of Si with Al in 0.2%C-1.5%Si-1.25%Mn-0.2%Cr ultrahigh strength transformation-induced plasticity (TRIP)-aided martensitic (TM) sheet steel improves galvanization. The effect of Al content on the microstructure and formabilities of the TM steel was therefore investigated. Replacement of Si with Al maintained the high volume fraction of the retained austenite and the high stretch-formability and stretch-flangeability, whereas it decreased the tensile strength. Complex addition of Si and Al yielded the best formabilities with 1.5 GPa tensile strength grade. The superior formabilities of Si-Al bearing TM steel were attributed to the strain-induced transformation of the metastable retained austenite and the relatively soft lath-martensite structure matrix. The former leads to plastic relaxation of the localized stress concentrations, thus suppressing void formation.

Mechanical Property Characterization of Aligned Plant Yarn Reinforced Thermoset Matrix Composites Manufactured via Vacuum Infusion

This article evaluates the mechanical properties of vacuum-infused unidirectional plant fiber composites (PFRPs), composing of bast fiber yarns and thermoset matrices. PFRPs are found to have lower fiber volume fractions than E-glass composites (GFRPs). Apart from the expected (30–40%) lower density of PFRPs, they have 60–80% lower tensile strength, 30–60% lower tensile stiffness, 5–10 times lower impact strength, and 20–30% lower interlaminar shear strength than GFRPs. Importantly, critical fiber lengths are of the same order (0.2–0.5 mm). Composites reinforced with flax rovings exhibit exceptional fiber tensile modulus of 65–75 GPa and fiber tensile strength of about 800 MPa.

Evolution of strength and microstructure during annealing of heavily cold-drawn 6.3 GPa hypereutectoid pearlitic steel wire

Hypereutectoid steel wires with 6.35GPa tensile strength after a cold-drawing true strain of 6.02 were annealed between 300 and 723K. The ultrahigh strength remained upon annealing for 30min up to a temperature of 423K but dramatically decreased with further increasing temperature. The reduction of tensile strength mainly occurred within the first 2–3min of annealing. Atom probe tomography and transmission electron microscopy reveal that the lamellar structure remains up to 523K. After annealing at 673K for 30min, coarse hexagonal ferrite (sub)grains with spheroidized cementite, preferentially located at triple junctions, were observed in transverse cross-sections. C and Si segregated at the (sub)grain boundaries, while Mn and Cr enriched at the ferrite/cementite phase boundaries due to their low mobility in cementite. No evidence of recrystallization was found even after annealing at 723K for 30min. The stability of the tensile strength for low-temperature annealing (<473K) and its dramatic drop upon high-temperature annealing (>473K) are discussed based on the nanostructural observations.

Effect of Zr on super-elasticity and mechanical properties of Ti–24at% Nb–(0, 2, 4)at% Zr alloy subjected to aging treatment

Abstract β-Type titanium alloys with composition of Ti–24 at% Nb–(0, 2, 4) at% Zr were prepared and subjected to aging treatment for different durations. The addition of Zr suppressed the formation and growth of isothermal ω phase during aging treatment, and therefore the investigated Ti–Nb–Zr alloys with different Zr content performed various deformation mechanisms, mechanical properties and super-elastic effects with the changes of aging time. The isothermal ω phase exerted inhibitory effects on twinning and stress-induced martensitic transformation. Desirable properties were obtained in Ti–Nb–Zr alloy by adding suitable Zr content and processing short time aging treatment. Ti–24 at% Nb–2 at% Zr alloy subjected to aging treatment at 573 K for 7.2 ks exhibited an ultimate tensile strength of 710 MPa, an elongation of 13%, a Young's modulus of 64 GPa, and a super-elastic recovery strain of 4.3%. Ti–24 at% Nb–4 at% Zr alloy subjected to aging treatment at 573 K for 1.8 ks, 3.6 ks, and 7.2 ks performed a low Young's modulus of 62 GPa and ultimate tensile strength around 600 MPa.

Strength and ductility of 316L austenitic stainless steel strengthened by nano-scale twin bundles

By means of dynamic plastic deformation (DPD) with high strain rates, a bulk nanostructured 316L austenitic stainless steel consisting of nano-sized grains embedded with bundles of nanometer-thick deformation twins was synthesized. The average transverse grain size is ∼33nm and the twin/matrix lamellar thickness is ∼20nm. The nano-twin bundles constitute ∼24% in volume. The nanostructured samples exhibit a high tensile strength of ∼1400MPa but a limited ductility with a uniform elongation of ∼2%. Subsequent thermal annealing of the as-DPD samples in a temperature range of 730–800°C led to a single-phased austenite structure consisting of static recrystallized (SRX) micro-sized grains embedded with remaining nano-twin bundles and nano-grains. The annealed DPD samples exhibit an enhanced strength–ductility synergy and much more enhanced work-hardening rates than the as-deformed samples. Work-hardening rates of the annealed DPD samples can be even higher than that of the original CG sample. Tensile ductility was found to increase almost linearly with the volume fraction of SRX grains. A combination of 1.0GPa tensile strength with an elongation-to-failure of ∼27% is achieved in the annealed DPD 316L stainless steel samples.

Mechanical properties of chicken feather fibers

AbstractChicken feather fibers (CFFs) are attractive for composite applications. In this study, mechanical properties of the feather barbs were investigated statistically. The strain at break of CFFs had a Gaussian distribution with a mean value of 6.93%. The tensile modulus of CFFs was 3.59 ± 1.09 GPa and average tensile strength was 203 ± 74 MPa, respectively. Both tensile modulus and tensile strength among different feathers were significantly different. The failure of the CFFs followed a Weibull distribution with a scale parameter value of 178.7 MPa and a shape parameter value of 2.32. Overall, the well‐investigated mechanical properties of the CFFs are beneficial for the further study of its applications in composite materials. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers

Effect of High-Pressure Torsion Processing and Annealing on Hydrogen Embrittlement of Type 304 Metastable Austenitic Stainless Steel

The effect of high-pressure torsion (HPT) and annealing on hydrogen embrittlement (HE) of a type 304 stainless steel was studied by metallographic characterization and tensile test after hydrogen gas charging. A volume fraction of ~78 pct of the austenite transformed to α′ martensite by the HPT processing at an equivalent strain of ~30. Annealing the HPT-processed specimen at a temperature of 873 K (600 °C) for 0.5 hours decreased the α′ martensite to ~31 pct with the average grain size reduced to ~0.43 μm through the reverse austenitic transformation. Hydrogen charge into the HPT-processed and the HPT+annealed specimens in the hydrogen content of ~10 to 20 ppm led to no severe HE but appeared in the solution-treated specimen. Especially the 873 K (600 °C) annealed specimen had the ~1.4 GPa tensile strength and the ~50 pct reduction of area (RA) despite the hydrogenation.