Deformation behavior of nanostructured aluminum alloy processed by severe plastic deformation

Microstructure and deformation behavior of the commercial aluminum-based Al7.5%Zn–2.7%Mg–2.3%Cu–0.15%Zr alloy subjected to high pressure torsion (HPT) were studied in the present work. A small grain size less than 100 nm, high level of internal stresses and presence of second phase nanoparticles were revealed by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The nanostructured alloy processed by HPT exhibits tensile strength of 800 MPa and ductility of 20% at optimal temperature-strain rate conditions. Unusual influence of a short pre-annealing on tensile strength and ductility of as-processed alloy is discussed.

Nanograin metals and metallic multilayers produced by severe plastic deformation

This research has developed an improved understanding of the structure-property relationships, fabrication technology and deformation mechanism of light bulk ultrafine grained materials and metallic multilayered structure.

Multimodal nanostructured titanium using severe plastic deformation

In the present study, multimodal nanostructured titanium was engineered using severe plastic deformation. The multimodal structured titanium exhibits an ultrahigh strength of over 940 MPa and a large failure elongation of 24%. The ultrahigh strength is mainly derived from the nanostructured structures; whilst the exceptional ductility originates from the large fraction of high angle grain boundaries, micro-scale structures, and the non-equilibrium grain boundary configuration. It is worth noting that apart from dislocation slip processes, the formation of deformation twins reduced the effective slip distance and increased the strain hardening capacity via the Hall-Petch mechanism, leading to high ductility of the multimodal structured titanium.

The biomedical application of Ti after severe plastic deformation and thermal oxidation, especially the friction and wear properties of Ti

Surface mechanical attrition treatment (SMAT), a novel surface severe plastic deformation method, was carried out for titanium (Ti) to create a gradient-structured Ti (SMAT Ti). The tribological behaviour was studied under different loads and dry sliding conditions. The results showed that the deformation layer of SMAT Ti was about 160 lm. The friction and wear results showed that the wear resistance of SMAT Ti was enhanced compared to the coarse-grained (CG) counterpart. SMAT Ti showed abrasive wear under 1 and 5 N, and exhibited abrasive and adhesive wear under 2 N. While CG Ti showed abrasive and adhesive wear under 1–2 N, and exhibited abrasive wear under 5 N for the work hardening effects.

Severe plastic deformation of TWIP steel

The severe plastic deformation of a Twinning Induced Plasticity (TWIP), 0.61C-22.3Mn-0.19Si-0.14Ni-0.27Cr (wt. %) steel by Equal Channel Angular Pressing (ECAP) at elevated temperatures was used to study the deformation mechanism as a function of accumulated strain and processing parameters. The relationship between the microstructures after different deformation schedules of ECAP at the temperatures of 200, 300 and 400oC, strain hardening behavior and mechanical properties was studied. The best balance between strength and ductility (1702 MPa and 24%) was found after 2 passes at 400oC and 300oC of ECAP. It was due to the formation of deformation microbands and twins in the microstructure. The twinning was observed after all deformation schedules except after 1 pass at 400oC. The important finding was the formation of twins in the ultrafine grains. Moreover, the stacking faults were observed in the subgrains with the size of 50nm. It is also worth mentioning the formation of nano- twins within the micro-twins at the same time. It was found that the deformation schedule affects the dislocation substructure with formation of deformation bands, cells, subgrains, two variants of twins that, in turn, influence the strain-hardening behavior and mechanical properties. Keywords: Twinning Induced Plasticity steels; Equal Channel Angular Pressing; mechanical properties; transmission electron microscopy; micro/nano twins; dislocation substructure.

Bimetallic copper-aluminium tube by severe plastic deformation

A new process of joining tubes from different materials to a bimetallic tube based on a combination of large shear and high hydrostatic pressure is proposed. It results in improved mechanical locking of surface asperities, along with enhanced diffusivity owing to the ultrafine-grained microstructure produced. This is augmented by a temperature increase due to heat release associated with mechanical work. Electron microscopy characterization of the interface and the adjacent regions supports the hypothesis of enhanced interdiffusion.

Enhancement of properties in cast Mg-Y-Zn rod processed by severe plastic deformation

Ternary Mg-Y-Zn alloys have attracted considerable attention from researchers due to their excellent mechanical properties and unique microstructures, particularly from the presence of long-period stacking-order (LPSO) phases. Microstructural variations and the resulting mechanical properties can be affected by various processing routes, particularly those involving severe plastic deformation of a cast billet. The approach used in this work was based on subjecting cast Mg92Y4Zn4 (composition in wt%) billet to severe plastic deformation by three different routes, namely equal channel angular pressing (ECAP), high pressure torsion (HPT) and ECAP followed by HPT, with the aim of refining the microstructure and improving mechanical properties. Samples processed by ECAP were annealed by post-processing and tested in compression and tension. The effect of the processing route and the process parameters on the microstructure and the hardness of the Mg-Y-Zn alloy is reported. An overall positive effect of annealing treatment on the mechanical properties of ECAP-processed alloy is demonstrated. © 2014 Elsevier B.V.

Severe plastic deformation processes with friction induced shear

Among the known severe plastic deformation (SPD) techniques, there is a special group of processes involving friction-induced shear. One of the sample or work-piece dimensions used in such processes, namely the thickness, is much smaller than the other two dimensions. The well-known process of High Pressure Torsion (HPT) and the relatively new Cone-Cone (CC) method applied to thin conical samples fall into this category of SPD techniques. Wrought aluminium alloy 2124 was used to study the effect of CC processing on microstructure and mechanical properties. The influence of the processing parameters, including the rotation speed and thickness of the conical strip specimens on the microstructure and the mechanical properties of the CC-processed material was investigated.

Microstructure and electrical conductivity of aluminium/steel bimetallic rods processed by severe plastic deformation

Equal-channel angular pressing (ECAP) was used to fabricate Al/steel bimetallic rod for potential application in overhead transmission conductors. Bimetallic rods consisted of an austenitic stainless steel 316L core and an Al alloy 6201 cladding layer. By means of ECAP processing at 175°C, increase of mechanical strength without loss of electrical conductivity was achieved for one particular rod geometry out of three geometries tested. X-ray diffraction and transmission electron microscopy were employed to analyse how the microstructure was influenced by the number of processing passes and the bimetallic rod geometry. The co-deformation mechanism of the bimetallic rod under ECAP and accelerated dynamic ageing of Al alloy 6201 were discussed based on the microstructure characterisation results.

Microstructure and properties of a C-Mn steel subjected to heavy plastic deformation

In the present paper an effect of severe plastic deformation (SPD) on the microstructural evolution and properties of a plain C-Mn steel was investigated. The SPD was accomplished by the MaxStrain system which deforms material along two perpendicular axes while the deformation along the third axis is fully constrained. The applied amounts of true strains were 5 and 20 in total. Deformation was conducted at room and 500°C temperatures. Some samples deformed at room temperature were subsequently annealed at 500°C. A microstructural analysis by SEM/EBSD was used for recognition the low- and high-angle grain boundaries. It was found that the collective effect of severe plastic deformation (true strain of 20) and further annealing promotes the formation of high-angle grain boundaries and uniform fine grained microstructure. The refinement of ferrite microstructure results in a significant increase in strength and hardness.

Effect of composition and austenite deformation on the transformation characteristics of low-carbon and ultralow-carbon microalloyed steels

Deformation dilatometry has been used to simulate controlled hot rolling followed by controlled cooling of a group of low- and ultralow-carbon microalloyed steels containing additions of boron and/or molybdenum to enhance hardenability. Each alloy was subjected to simulated recrystallization and nonrecrystallization rolling schedules, followed by controlled cooling at rates from 0.1 °C/s to about 100 °C/s, and the corresponding continuous-cooling-transformation (CCT) diagrams were constructed. The resultant microstructures ranged from polygonal ferrite (PF) for combinations of slow cooling rates and low alloying element contents, through to bainitic ferrite accompanied by martensite for fast cooling rates and high concentrations of alloying elements. Combined additions of boron and molybdenum were found to be most effective in increasing steel hardenability, while boron was significantly more effective than molybdenum as a single addition, especially at the ultralow carbon content. Severe plastic deformation of the parent austenite (>0.45) markedly enhanced PF formation in those steels in which this microstructural constituent was formed, indicating a significant effective decrease in their hardenability. In contrast, in those steels in which only nonequilibrium ferrite microstructures were formed, the decreases in hardenability were relatively small, reflecting the lack of sensitivity to strain in the austenite of those microstructural constituents forming in the absence of PF.

Plastic deformation in Zr41 Ti14 Cu12.5 Ni10 Be22.5 bulk metal glass under vickers indenter

Vickers indentation was conducted on an as-cast Zr41Ti14Cu12.5Ni10Be22.5 bulk metal glass (BMG) to study shear band formation using a bonded interface technique. The results indicate that the plastic deformation in the BMG is accommodated by the semi-circular (primary) and radial (secondary) shear bands. The inter-band spacing of the semi-circular shear bands is found to be independent of the applied load. The measured size of the deformation zone is in good agreement with the prediction of the theoretical model proposed by Zhang et al.