Good Tensile Ductility Research Articles

High tensile-strength and ductile titanium matrix composites strengthened by TiB nanowires

A three-dimensional network-woven architecture made of TiB nanowires has been designed and realized in the matrix of a Ti6Al4V alloy. The architecturally nanostructured design was achieved by dispersing nanoparticles of B4C or B onto the surfaces of spherical Ti6Al4V powder particles via mechanical mixing and subsequent consolidation by spark plasma sintering. The as-sintered nanostructured Ti6Al4V-TiB composites demonstrated excellent tensile strengths and ductility that are required for critical applications. The in situ formed TiB nanowires with aspect ratios up to 300 contributed to the high tensile strengths while the architectural design of the TiB nanowires ensured the good tensile ductility.

Mechanical properties and structure of AZ61 magnesium alloy processed by equal channel angular pressing

An equal channel angular pressing (ECAP) procedure has been developed to produce a fine-grained AZ61 magnesium alloy. The results show that the microstructure can be effectively refined with increasing equivalent strain during ECAP. For increasing ECAP process efficiency was conventional tool as a helix in the horizontal part of channel built. This fine-grained alloy has an excellent strength accompanied by reasonable good tensile ductility. The success of the development of this ECAP procedure can offer a good opportunity for the development of magnesium alloys with good mechanical properties.

A ductile high entropy alloy with attractive magnetic properties

FeCoNiMn0.25Al0.25 high entropy alloy was investigated thoroughly in this paper from crystal structure to magnetic and mechanical properties. We found that this alloy formed simple face centered cubic structure which was very stable to deformation and heat treatment. Moreover, this alloy showed high saturated magnetization, low coercivity, high Curie temperature as well as good tensile ductility. This high entropy alloy shows soft magnetic properties much better than most high entropy alloys reported previously. This study suggests that the FeCoNiMn0.25Al0.25 high entropy alloy has the potential for use as soft magnets in the future.

Fabrication of a 2014Al-SiC/2014Al Sandwich Structure Composite with Good Tensile Strength and Ductility

A sandwich structure laminate composed of a ductile 2014Al inter-layer and two nanoscale SiC reinforced 2014Al (SiC/2014Al) composite outer layers was successfully fabricated through the combination of powder metallurgy and hot rolling. The ductile 2014Al inter-layer effectively improved the processability of the sandwiched laminates. Tensile test revealed that the yield strength and ultimate tensile strength of the sandwiched laminate were 287 and 470 MPa, respectively, compared with 235 and 425 MPa for monolithic 2014Al. The good performance of the sandwiched laminate results from the strong bonding between the SiC/2014Al composites layer and the ductile 2014Al layer. Thus, the sandwich structure with a composite surface and ductile core is effective for increasing the strength and toughness of composite laminates.

Tailoring nanostructures and mechanical properties of AlCoCrFeNi2.1 eutectic high entropy alloy using thermo-mechanical processing

The effect of thermo-mechanical processing on the evolution of microstructure and mechanical properties was investigated in an AlCoCrFeNi2.1 high entropy alloy. For this purpose, the alloy was cold-rolled to 90% reduction in thickness and annealed at temperatures ranging from 800°C to 1200°C. The as-cast alloy revealed eutectic lamellar mixture of (Ni, Al) rich but Cr depleted B2 phase and Al-depleted L12 phases, having volume fractions of ~35% and 65%, respectively. Nanosized precipitates enriched in Cr and having disordered BCC structure were found dispersed inside the B2 phase. Cold-rolling resulted in progressive disordering of the L12 phase but the B2 phase maintained the ordered structure. The disordering of the L12 phase was accompanied by the evolution of ultrafine lamellar structure and profuse shear band formation. Annealing of the 90% cold-rolled material at 800°C resulted in the formation of a duplex microstructure composed of two different phases with equiaxed morphologies, having significant resistance to grain growth up to 1200°C. The annealed materials showed disordered FCC and precipitate-free B2 phases. This indicated that quenching of the annealed specimens to room temperature was sufficient to prevent the ordering of the L12 phase and the formation of the Cr-rich nano-precipitates which were dissolved in the B2 phase during annealing. Significant improvement in tensile properties compared to the as-cast alloy could be achieved by thermo-mechanical processing. All the specimens annealed at 800°C to 1200°C were having good tensile ductility over 10% as well as high tensile strength greater than 1000MPa. These indicated that the properties of the EHEA could be successfully tailored using thermo-mechanical processing for a wide range of engineering applications.

Effect of Phase Transformation Conditions on the Microstructure and Tensile Properties of Ti-3Al-15Mo-3Nb-0.2Si Alloy

The influence of phase transformation conditions (α/β solution treatment plus aging, β solution treatment plus aging, and β solution treatment plus duplex aging) on the microstructure and tensile properties of Ti-3Al-15Mo-3Nb-0.2Si alloy was studied. Microstructure observation indicates that the primary α phase, which formed during α/β solution treatment, can effectively limit the growth of the β grains. The alloy was heat treated in the α/β solution, which together with aging, formed smaller grains and finer precipitates in the sample and showed good tensile ductility with a 15% elongation. Aging temperatures from 450 to 600 °C were used to study the effects of aging treatment on the alloy’s microstructure and tensile properties. Precipitation phases appeared in particular positions (αGB, αWGB, and αWM) during the aging process which depended on phase transformation conditions and caused variations in the alloy’s tensile properties. The alloy treated by duplex aging after β solution had a higher ultimate tensile strength at 1370 MPa than that of other samples, resulting from the finer α precipitates transformed from the ω phases. The relationship of tensile properties and phase transformation was investigated by observing the material fracture, and small and dense dimples were seen in the tensile specimen treated by α/β solution plus aging treatment which led to excellent ductility. Deep dimples in the duplex aging specimen resulted in beneficial high strength.

Mechanical Behavior of Ultrafine Gradient Grain Structures Produced via Ambient and Cryogenic Surface Mechanical Attrition Treatment in Iron

Ambient and cryogenic surface mechanical attrition treatments (SMAT) are applied to bcc iron plate. Both processes result in significant surface grain refinement down to the ultrafine-grained regime; the cryogenic treatment results in a 45% greater grain size reduction. However, the refined region is shallower in the cryogenic SMAT process. The tensile ductility of the grain size gradient remains low (<10%), in line with the expected behavior of the refined surface grains. Good tensile ductility in a grain size gradient requires the continuation of the gradient into an undeformed region.

The Effect of Thermomechanical Treatment on the Microstructure and the Mechanical Behavior of a Supersaturated Cu-Ag Alloy

Supersaturated Cu-3at.% Ag alloy was processed by cold rolling and short-time annealing in order to achieve a combination of high strength and good tensile ductility. After annealing of the rolled samples a heterogeneous solute atom distribution was developed due to the dissolution of nanosized Ag particles in some volumes of the matrix. In regions with higher solute content, the high dislocation density formed due to rolling was stabilized, while in other volumes the dislocation density decreased. The heterogeneous microstructure obtained after annealing exhibited a much higher ductility and only a slightly lower strength than in the as-rolled state.

Bulk metallic glass composite with good tensile ductility, high strength and large elastic strain limit

Bulk metallic glasses exhibit high strength and large elastic strain limit but have no tensile ductility. However, bulk metallic glass composites reinforced by in-situ dendrites possess significantly improved toughness but at the expense of high strength and large elastic strain limit. Here, we report a bulk metallic glass composite with strong strain-hardening capability and large elastic strain limit. It was found that, by plastic predeformation, the bulk metallic glass composite can exhibit both a large elastic strain limit and high strength under tension. These unique elastic mechanical properties are attributed to the reversible B2↔B19′ phase transformation and the plastic-predeformation-induced complicated stress state in the metallic glass matrix and the second phase. These findings are significant for the design and application of bulk metallic glass composites with excellent mechanical properties.

Enhancement in mechanical properties of bulk nanocrystalline Fe–Ni alloys electrodeposited using propionic acid

A method for enhancement of the mechanical properties of electrodeposited bulk nanocrystalline Fe–Ni alloys was explored. Bulk nanocrystalline Fe–Ni alloys were prepared using electrolytes that primarily consisted of iron sulfate and nickel sulfamate with propionic acid. Varying the concentration of propionic acid in the deposition bath produced no significant change in the C, S, or Ni content or grain sizes of the electrodeposited alloys. In contrast, the hardness of bulk nanocrystalline Fe–Ni alloys increased from 4.0 to 5.0GPa with the increase of propionic acid concentration from 0 to 3.0g/L. In addition, the tensile strength also increased from 1.6 to 1.7GPa while maintaining a good tensile ductility of ~10%. These increases for electrodeposited alloys can be explained by grain boundary relaxation strengthening. After annealing at relatively mild temperatures, the alloys electrodeposited without propionic acid exhibited higher strength than at the as-deposited state, while the strength of the alloys electrodeposited using 3.0g/L propionic acid remained unchanged. The results of this study indicate that the addition of propionic acid to the deposition bath could remove the excess grain boundary defects of Fe–Ni alloys in as-deposited states, requiring no additional thermal treatments and enhancing the mechanical strength to high levels.

Synthesis of a TiBw/Ti6Al4V composite by powder compact extrusion using a blended powder mixture

A Ti–6wt%Al–4wt%V alloy (Ti6Al4V) matrix composite, reinforced by in situ synthesized TiB whiskers (TiBw) has been successfully fabricated by powder compact extrusion using a blended powder mixture. The microstructural characterization of the various extruded samples showed that the different starting powders, pre-alloyed powder plus boron powder or titanium plus Al–40V master alloy powder plus boron powder, had a significant effect on the morphology of the in situ synthesized TiB whiskers. It is also evident that the TiB whiskers affect the microstructural evolution of the Ti6Al4V matrix. The tensile test results indicated that the composite with a dispersion of fine TiB whiskers with high aspect ratios exhibited a high ultimate tensile stress (UTS) and yield stress (YS) of 1436MPa and 1361MPa, respectively, a reasonably good tensile ductility reflected by an elongation to fracture of 5.6% was also achieved. This is a significant improvement compared with as-extruded monolithic Ti6Al4V alloy produced in this study.

Pre-electrodeposition process for improving tensile ductility of Al electrodeposited from a dimethylsulfone bath

Al was electrodeposited from a dimethylsulfone (DMSO2) bath using a new pre-electrodeposition process to investigate the effect of sulfur and chlorine on the tensile ductility. Al electrodeposited from a DMSO2 bath contains sulfur and chlorine, which are impurities are incorporated into the electrodeposits as sulfide and chloride, respectively. By pre-electrodeposition, the sulfur and chlorine contents of electrodeposited Al decreased from approximately 0.64 and 0.71at% to 0.15 and 0.17at%, respectively. This reduction in the sulfur and chlorine contents affects the microstructure, hardness, and ductility of the electrodeposits. The grain size increased from approximately 200nm to 4μm, and the microhardness decreased from 1.67 to 0.24GPa. In tensile tests, electrodeposited Al before pre-electrodeposition exhibited failure even in the elastic regime, while electrodeposited Al after pre-electrodeposition exhibited good tensile ductility of approximately 30%.

Effect of additives on tensile properties of bulk nanocrystalline Ni–W alloys electrodeposited from a sulfamate bath

Abstract Ni–W alloys are promising materials for high temperature and structural applications. However, they show no plastic deformation under tensile tests. We electrodeposited bulk nanocrystalline Ni–W alloys from sulfamate baths that contained different additives, such as saccharin sodium, 2-butyne-1,4-diol, and sodium allylsulfonate, to improve the tensile ductility. Their orientation, microstructure and tensile behavior significantly differed. In particular, the sample deposited from a sulfamate bath that contained saccharin sodium exhibited a stronger (200) texture and good tensile ductility of approximately 5.0%. These experiments indicate that control of the texture is important to enhance the tensile ductility of electrodeposited bulk nanocrystalline Ni–W alloys.

Room and high temperature deformation behaviour of a forged Fe–15Al–5Nb alloy with a reinforcing dispersion of equiaxed Laves phase particles

The cast-in network of continuous Laves phase in a Fe–15%Al–5%Nb alloy has been converted to a dispersion of coarse Laves phase particles by high temperature forging, and the room temperature and high temperature deformation behaviour examined. The material shows good room temperature tensile ductility and good creep strength at temperatures up to 700°C. The good high temperature strength is explained by the refinement of substructure by the dispersion of Laves phase particles and load and strain partitioning between the stiff and hard phase and the softer matrix. The relatively coarse microstructure is expected to be highly stable against coarsening at high temperatures, which should allow retention of creep properties even for long exposure times.

Effects of warm rolling and ageing after cryogenic rolling on mechanical properties and microstructure of Al 6061 alloy

The mechanical properties and microstructural evolution of Al 6061 alloy subjected to cryorolling and warm rolling have been investigated in the present work. The Al 6061 alloy was subjected to thickness reduction of 70% by cryorolling followed by thickness reduction of 20% by warm rolling. The cryorolled+warmrolled (CR+WR) samples were characterized by Electron back scattered diffraction (EBSD) technique, Differential scanning calorimetry (DSC), X-Ray diffraction (XRD) analysis and Transmission electron microscopy (TEM) technique to substantiate the role of deformation strain and temperature on their microstructural features and compared with cryorolled (CR) samples. The CR+WR samples showed a significant improvement in tensile strength (376MPa) and partial improvement in ductility (5%) as measured from tensile testing. It is mainly due to the combined effect of partial grain refinement, solid solution strengthening, dislocation hardening, dynamic recovery, and dynamic ageing during cryorolling and warm rolling. The effect of ageing on CR+WR samples was investigated and the optimum ageing condition was found to be 45h at 125°C, which gives improved tensile strength of (406MPa) and good tensile ductility (10%). The tensile strength of cryorolled+warm rolled+peak aged (CR+WR+PA) sample (406MPa) was found to be 11.2% more than that of cryorolled+peak aged (CR+PA) sample (365MPa). During peak ageing treatment, the strength has been retained by pinning of dislocations through nanosized precipitates generated during warm rolling and it has been improved further by precipitation of the remnant dissolved second phase in the matrix. However, the observed ductility of CR+PA sample was 13% more than CR+WR+PA sample due to low dislocation density after ageing.

Grain refinement in an as-cast AZ61 magnesium alloy processed by multi-axial forging under the multitemperature processing procedure

Abstract A multitemperature multi-axial forging (MAF) procedure has been developed to produce a fine-grained AZ61 alloy. The results show that the microstructure can be effectively refined with increasing equivalent strain during MAF. Once dynamic recrystallisation is completed, the alloy is in a steady state and further deformation of the alloy cannot change the grain size. The multitemperature MAF procedure can produce a fine-grained AZ61 alloy giving a grain size of 8 μm. This fine-grained alloy has an excellent strength accompanied by reasonable good tensile ductility. The success of the development of this multitemperature MAF procedure proves that MAF can offer a good opportunity for the development of magnesium alloys with good mechanical properties.

Effect of ageing on microstructure and mechanical properties of bulk, cryorolled, and room temperature rolled Al 7075 alloy

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 are has been investigated in the present work employing hardness measurements, tensile test, XRD, DSC, and TEM. The solution-treated bulk Al 7075 alloy was subjected to cryorolling and room temperature rolling to refine grain structures and subsequently ageing treatment to simultaneously improve the strength and ductility. The solution treatment combined with cryorolling up to a true rolling strain of 2.3 followed by low temperature ageing at 100 °C for 45 h has been found to be the optimum processing condition to obtain fine grained microstructure with improved tensile strength (642 MPa) and good tensile ductility (9.5%) in the Al 7075 alloy. The combined effect of suppression of dynamic recovery, partial grain refinement, partial recovery, solid solution strengthening, dislocation hardening, and precipitation hardening are responsible for the significant improvement strength–ductility combination in the cryorolled Al 7075 alloy subjected to peak ageing treatment. The cryorolled and room temperature rolled Al 7075 alloy, upon subjecting to peak ageing treatment, have shown higher strength and ductility in the former than the latter. It is due to presence of high density of nanosized precipitates in the peak aged cryorolled sample.

IMPROVED MECHANICAL PROPERTY OF ELECTRODEPOSITED NANOCRYSTALLINE NICKEL-COBALT ALLOY

A bulk and dense nc Ni -24.7% Co with an average grain size of 15nm was fabricated by a direct current electrodeposition. This Ni -24.7% Co exhibits very high tensile strength of 1813MPa to 2232MPa with relatively good tensile ductility of 6.0%~9.6% under tensile test over a wide strain rate range of 0.417s-1 ~ 1.35×10-5s-1. The combination of high strength and good ductility should be attributed to the increased strain hardening ability induced by the addition of alloying Co element. The interaction of dislocation and grain boundaries is the rate-controlling deformation mechanism controlled in the Ni -24.7% Co based on its high strain rate sensitivity of 0.029 and small activity volume of ~14b3.

A Study on the Combined Treatment of Cryorolling, Short-Annealing, and Aging for the Development of Ultrafine-Grained Al 6063 Alloy with Enhanced Strength and Ductility

High-strength ultrafine-grained (UFG) metals and alloys often show a reduced tensile ductility when compared with their coarse-grained counterparts. The earlier attempts in trying to improve their ductility usually have led to sacrificing its strength. Optimized process conditions are proposed to achieve both high strength and high ductility in the Al 6063 alloy in the current work. It involves solution treatment of the Al 6063 alloy to dissolve the second-phase particles, cryorolling (CR) to produce a high density of dislocations, short annealing (SA) treatment to recrystallize partially the microstructure without affecting the age-hardening effect, and finally aging treatment to generate highly dispersed nano precipitates. The solution treatment prior to CR combined with post-CR SA at 428 K (155 °C) for 5 minutes followed by aging treatment at 398 K (125 °C) for 12 hours are the optimum processing conditions to obtain the UFG microstructure with improved tensile strength (286 MPa) and good tensile ductility (14 pct) in the Al 6063 alloy. It is observed that the accumulation of dislocations and the formation of nanosized precipitates are responsible for improving the strength, whereas both a low dislocation density and a high density of nanosized precipitates contribute to the improvement in ductility of the CR Al 6063 alloy subjected to an optimized treatment of short annealing and aging.

Effect of Ageing on Strength and Ductility of Ultrafine Grained Al 6061 Alloy

An effect of ageing on mechanical properties of ultrafine grained Al 6061 alloys has been investigated in the present work. The solution treated bulk Al 6061 alloy was subjected to cryorolling to produce ultrafine grain structures and subsequently ageing treatment to improve its both strength and ductility. The hardness and tensile properties of solution treated, cryorolled, cryorolled and aged Al alloys were measured and explained by using their corresponding microstructural morphologies. The pre-cryorolled solid solution treatment combined with post-CR ageing treatment (1300C-30h) has been found to be the optimum processing condition to obtain the ultrafine grained microstructure with improved tensile strength (362MPa) and good tensile ductility (10.7%) in the Al 6061 alloy. The combined effect of precipitation hardening and recovery are responsible for the simultaneous improvement of both strength and ductility observed in the present work.