Effect Of Severe Plastic Deformation Research Articles

Ageing Characteristics of Equal Channel Angular Pressed Al-Mg-Si Alloy

This study investigated the effect of severe plastic deformation (SPD) and artificial ageing treatment on mechanical properties of cast Al-Mg-Si alloy. 6061-T6 aluminum alloy was remelted and casted into a rod of 13mm in diameter and 60mm in length. The rod samples were then subjected to equal channel angular pressing (ECAP) for SPD process, up to 2 passes, through Bc route. Cast and ECAPed samples were solution heat treated at 530 °C, quenched in water and held at 180 °C at various ageing time to determine the effect of artificial ageing. Cast alloy consisted of α phase grains that were surrounded by Mg2Si particles locating at the grain boundaries. The hardness increased with accumulative applied strain by 2-pass ECAP process with the value of 99.4 Hv. For heat treated samples, maximum hardness was achieved after 5-hour ageing.

Assessment of anisotropic tensile strength using a modified shear punch test for Cu–Cr–Zr alloy processed by severe plastic deformation

The effect of severe plastic deformation on the anisotropic strength change was investigated by equal-channel angular pressing (ECAP) experiments with various pass numbers. To overcome the size limitation for the tensile test specimen, this study proposes a shear punch test modified by using a flat-end rectangular punch to evaluate uniaxial tensile strength in multiple directions in the longitudinal and transverse sections of the ECAP-processed Cu–Cr–Zr alloy. The validity of the modified method was verified by the linear relationship between the shear punch test data and tensile test data in the longitudinal direction. Specimens were prepared at three angles (0°, 45° and 90°) with respect to the extrusion direction in the longitudinal sections and the horizontal direction in the transverse sections of the ECAP bar. The results showed that tensile strength deceased when the angle increased from 0° to 90° in both the longitudinal and transverse sections. The longitudinal sections showed a more pronounced anisotropy than the transverse sections. As the amount of plastic deformation by ECAP increased, the degree of the anisotropy decreased in the longitudinal section but increased in the transverse section. Based on the results of this study, the strength of an ECAP material must be assessed in multiple directions in both the longitudinal and transverse sections.

Effect of severe plastic deformation on hot cracking of wrought aluminium alloy in pulsed laser welding

The effect of friction stir processing (FSP) on the behaviour of wrought alloy 2024 in pulsed laser welding was examined. The results showed that FSP changes the microstructure and that significantly affects the susceptibility of the base metal to liquation cracking. The change in cracking behaviour is proposed to be related to the refinement of the microstructure and redistribution of precipitates along the grain boundaries, increasing the flexibility of the grain network. According to the observations, as a result of FSP, not only liquation cracks but also solidification cracks were reduced, supporting the view that liquation cracks can act as the source of some of the solidification cracks.

Effect of Severe Plastic Deformation at Ambient Temperature on Microstructures and Mechanical Properties of Aluminum Alloy 2519

The effect of severe plastic deformation at ambient temperature on microstructures and mechanical properties of aluminum alloy 2519 was investigated by means of tensile test, micro-hardness test, optical microscopy and scanning electron microscopy. The results showed that tensile strength of as-queched 2519 alloy was greatly enhanced to nearly 550MPa (ultimate tensile strength, UTS) and 520MPa (yield strength, YS) by severe cold rolling or equal channel angular processing (ECAP) while the elongation decreased to 5%. The 2519 alloy could obtain quite well mechanical properties as much as 80 % and 12 passes cold rolling deformation. This indicated that pre-deformation by ECAP is effective in improving the mechanical properties of 2519 alloy by grain refinement, strain aging and high density dislocations.

Effect of severe plastic deformation on creep behaviour of a Ti–6Al–4V alloy

This paper examines the effect of severe plastic deformation on creep behaviour of a Ti–6Al–4V alloy. The processed material with an ultrafine-grained (UFG) structure (d ≈ 150 nm) was prepared by multiaxial forging. Uniaxial constant stress compression and constant load tensile creep tests were performed at 648–698 K and at stresses ranging between 300 and 600 MPa on the UFG processed alloy and, for comparison purposes, on its coarse-grained (CG) state. The values of the stress exponents of the minimum creep rate n and creep activation energy Q c were determined. Creep behaviour was also investigated by nanoindentation method at room temperature under constant load. The microstructure was examined by transmission electron microscopy and scanning electron microscope equipped with an electron back scatter diffraction unit. The results of the uniaxial creep tests showed that the minimum creep rates of the UFG specimens are significantly higher in comparison with those of the CG state. However, the differences in the minimum creep rates of both states of alloy strongly decrease with increasing values of applied stress. The CG alloy exhibits better creep resistance than the UFG one over the stress range used; the minimum creep rate for the UFG alloy is about one to two orders of magnitude higher than that of the CG alloy. The indentation creep tests showed that annealing had little effect on the creep behaviour in UFG Ti alloy at room temperature.

The effect of severe plastic deformation and subsequent annealing on the structure and mechanical properties of titanium alloy PT-3V

The effect of severe plastic deformation by multi-axial pressing followed by thermal treatment on the structure and mechanical properties of titanium alloy PT-3V (4.66% Al : 1.92% V) has been investigated. Submicrocrystalline structure formation is shown to dramatically improve the mechanical properties of the alloy at room temperature and to decrease the superplastic flow temperature interval by 250–300 K. Lowtemperature annealing of the material in a submicrocrystalline state is found to cause further increase in the yield strength and ultimate strength as compared to the preannealing level, with the strain at fracture being nearly doubled.

Resistance of alloy Zr – 2.5% Nb with ultrafine-grain structure to stress corrosion cracking

The effect of severe plastic deformation of commercial alloy Zr – 2.5% Nb by the method of equal-channel angular pressing on the mechanisms and kinetics of stress corrosion cracking in a 1% “iodine – methanol” medium is studied. Quantitative comparative data on corrosion resistance of the alloy with ultrafine-grain structure after equal-channel angular pressing and with coarse-grain structure after the traditional treatment are obtained.

Effect of severe plastic deformation on microstructure and mechanical properties of bulk AZ31 magnesium alloy

The equal channel angular pressing (ECAP) was used to make large plastic deformation of magnesium alloy, and ECAP processing and relevant process parameters were obtained by using finite element method. The strain distributions in the workpieces and the loads on the dies were studied. The mathematical model of accumulated deformation results, microstructure refinement and mechanical properties were established. Through the analysis, the relationships between grain refinement and mechanical properties were obtained. The refined grain size and the obtained mechanical properties are forecasted by using characterization of accumulation deformation.

Grain Refinement in Al-Si-Cu Alloy During Cyclic Extrusion

The effect of severe plastic deformation (SPD) during cyclic extrusion (CE) on grain refinement and strain hardening in AlSiCu alloy is studied quantitatively.New experimental results are presented showing that the average of grain size decrease below 130nm, i.e. a nanocrystalline material is obtained. In the modelling part, the decrease in size of dislocation cells and micro bands is expressed in terms of the effective plastic strain defined such that strain rate reversals slow down its accumulation. Examples of microstructure of tested alloy severely deformed by cyclic extrusion are given as experimental results.

Effects of ECAP and Aging on Mechanical and Superelastic Behaviors of Ti-Mo-Based and Ti-25at.%Nb SMAs

Ni-free Ti-based shape memory alloys (SMAs) are increasingly recognized as promising functional materials for medical applications. The mechanical properties of these metastable Ti-based SMAs are sensitive to aging and thermomechanical treatment. Effects of severe plastic deformation (SPD)-equal channel angular pressing (ECAP) and aging on superelastic behavior of Ni-free Ti-based SMAs, Ti-9.8Mo-3.9Nb-2V-3.1Al wt.% (TMNVA) and Ti-25at.%Nb, have been investigated. The results show that the yielding strength of TMNVA alloy increases sharply with the number of ECAP processes—to greater than 1,400 MPa after two passes ECAP—but elongation of TMNVA alloy decreases severely and the plasticity is lost completely after two passes ECAP. Both ECAP process and flash annealing treatment have weak contribution to the superelastic recoverable strains of Ti-Mo-based alloy. For Ti-25at.%Nb alloy, after one pass ECAP process at 400 °C, the yielding stress increases obviously, and the recovery strain increases a little. With the further increase in the number of ECAP processes, the yielding stress and the recovery strain change little. Aging treatment at low temperature after ECAP process is in favor of superelasticity of Ti-25at.%Nb alloy. An almost completely recoverable strain of 1.5% is obtained in Ti-25at.%Nb alloy after two passes ECAP and aging at 300 °C for 1 h. The mechanisms of the effects of SPD and aging are also discussed.

Severe plastic deformation of rheoforged aluminum alloy A356

In this research, the electromagnetic stirring (EMS) process was used to produce semi-solid slurry with globular structure from cast A356 aluminum alloy. Then the slurry was forged in a die, which named rheoforging process. Utilizing multidirectional forging (MDF), the effect of severe plastic deformation on microstructure and mechanical properties of this alloy in dendritic and globular states was investigated. Shear punch, micro- and macro-hardness tests were used to study the mechanical properties of these samples. For metallographic examinations, the optical microscope equipped with the Clemex® image analyzer software was used. Optimum globular structure of rheoforged specimens was achieved to deform those in three successful passes of MDF. The results show that more severe strain can be imposed on globular structure with respect to dendritic one. Also, MDF process can effectively improve the strength of the samples with no noticeable change in globules morphology of the rheoforged samples.

Effect of Severe Plastic Deformation in Machining Elucidated via Rate-Strain-Microstructure Mappings

Machining induces severe plastic deformation (SPD) in the chip and on the surface to stimulate dramatic microstructural transformations which can often result in a manufactured component with a fine-grained surface. The aim of this paper is to study the one-to-one mappings between the thermomechanics of deformation during chip formation and an array of resulting microstructural characteristics in terms of central deformation parameters–strain, strain-rate, temperature, and the corresponding Zener–Hollomon (ZH) parameter. Here, we propose a generalizable rate-strain-microstructure (RSM) framework for relating the deformation parameters to the resulting deformed grain size and interface characteristics. We utilize Oxley’s model to calculate the strain and strain-rate for a given orthogonal machining condition which was also validated using digital imaging correlation-based deformation field characterization. Complementary infrared thermography in combination with a modified-Oxley’s analysis was utilized to characterize the temperature in the deformation zone where the SPD at high strain-rates is imposed. These characterizations were utilized to delineate a suitable RSM phase-space composed of the strain as one axis and the ZH parameter as the other. Distinctive one-to-one mappings of various microstructures corresponding to an array of grain sizes and grain boundary distributions onto unique subspaces of this RSM space are shown. Building on the realization that the microstructure on machined surfaces is closely related to the chip microstructure derived from the primary deformation zone, this elucidation is expected to offer a reliable approach for controlling surface microstructures from orthogonal machining.

Mechanical and microstructural aspects of severe plastic deformation of austenitic steel

The paper presents the effects of severe plastic deformation by multiple compression in the orthogonal directions on the microstructure and the mechanical properties of austenitic steel. Several deformation variants were conducted with different number of passes. FEM simulations were performed in order to evaluate the actual values of the effective strain in the examined, central parts of the compressed samples. The deformed microstructure was investigated by means of the scanning transmission electron microscopy (STEM) and the scanning electron microscopy (SEM) supported by the electron back scattered diffraction (EBSD). X-ray phase analysis was performed to evaluate the martensite volume fraction. The mechanical properties were determined by means of the digital image correlation method and hardness testing. It is shown that the applied forming technique leads to strong grain refinement in the austenitic steel. Moreover, deformation induces the martensitic γ– α' transformation. The microstructural changes cause an improvement in the strength properties. The material exhibits the ultimate tensile strength of 1560 MPa and the yield stress of 1500 MPa after reaching the effective strain of 10.

The effects of severe plastic deformation on some properties relevant to Ti implants

In some types of surgical implants, such as bone screws and plates, Grade 2 Ti is seriously considered as a replacement for the Ti-6Al-4V alloy. Advantages are lower cost and the absence of Al and V, which have been identified as potentially harmful to human health. The present paper shows that the lower strength of the commercially pure metal can be enhanced by Severe Plastic Deformation followed by conventional cold rolling, so as to reach a strength level higher than the technical requirements applicable to the alloy. This was ascertained by tensile and Vickers hardness tests from which it was concluded that the best combination of properties are obtained by submitting the metal to Equal Channel Angular Pressing (four passes at 300 °C) followed by a 70% thickness reduction by cold rolling. Although the present results are valid for the material only, and not for the product considered, that is, bone screws, it appears that this solution is a step towards the replacement of the Ti6-4 alloy by Grade 2 Ti, at least for some types of metallic medical implants.

The effect of high-pressure torsion on the behaviour of intermetallic particles present in Al–1Mg and Al–3Mg

The effect of severe plastic deformation on intermetallic particles was investigated using high-pressure torsion on an Al–1Mg–0.2Si–0.2Fe–0.3Mn alloy and an Al–3Mg–0.2Si–0.2Fe–0.3Mn (wt%) alloy. Extensive optical microscopy and scanning electron microscopy was performed to analyse the intermetallic particles using image analysis software. It was found that all the intermetallic particles decreased in size with increasing strain whilst their spatial distribution was homogenised. A greater decrease in size was found for the intermetallic particles present in Al–1Mg alloy and the possible causes are discussed. Even though the strain near the centre of the sample is close to zero, refinement of intermetallic particles is substantial at this location.

Effect of SPD and friction stir welding on microstructure and mechanical properties of Al–Cu–Mg–Ag sheets

Ultrafine grained (UFG) structure with an average grain size of ~ 0.6 μm was produced in sheets of Al–Cu–Mg–Ag alloy by equal channel angular pressing (ECAP) followed by hot rolling (HR) at 250 °C. These sheets were joined by friction stir welding (FSW) with efficiency of about unity. The effect of severe plastic deformation (SPD), FSW and heat treatment on the microstructure and mechanical properties of the welds and sheets was examined.

Research of magnesium alloys of the Mg-Sm-Y system subjected to severe plastic deformation and subsequent heat treatment

The effect of severe plastic deformation and subsequent aging on the structure and properties of cast and hardened magnesium alloys containing samarium and yttrium is studied. Severe plastic deformation leads to additional hardening both before and after aging. Hardening is achieved by the formation of nanocrystalline structure in quenched alloys or submicrocrystalline structure in cast alloys. Severe plastic deformation results in the rapid decomposition of a supersaturated magnesium solid solution and additional hardening due to the formation of nano-sized particles of hardening phases.

Effect of plastic deformation on physical properties and structure of the shape memory alloy Ti49.5Ni50.5

The effect of severe plastic deformation by torsion (SPDT) in Bridgman anvils at a high pressure (6 GPa) on the physical properties and crystal structure of the shape memory alloy Ti49.5Ni50.5 has been studied. The behavior of the thermal expansion, electrical resistivity, absolute differential thermopower, Hall coefficient, magnetic properties, and optical characteristics of the amorphous/nanocrystalline and submicrocrystalline alloys obtained by the SPDT with subsequent heat treatment at 800 K has been discussed.

Role of severe plastic deformation on the formation of nanograins and nano-sized precipitates in Fe–Ni–Mn steel

In this research, the effect of severe plastic deformation (SPD) on the formation of nano-scaled grains and precipitation of nano-sized particles which consequently control mechanical properties of Fe–Ni–Mn alloy was investigated. Fe–Ni–Mn martensitic steels show excellent age hardenability but suffer from embrittlement after aging. Discontinuous coarsening of grain boundary precipitates, resulting in the formation of precipitate free zone (PFZ) along prior austenite grain boundaries, has been found as the main source of embrittlement in the previous studies. In this paper, severe plastic deformation has been carried out on the Fe–10Ni–7Mn steel to improve its mechanical properties. It is found that substantial improvement of tensile properties in cold-rolled steels occurs at thickness reductions larger than 60% where formation of ultrafine grains is realized. According to transmission electron microscopy (TEM) observations, formation of nano-scaled grains less than 100 nm along with the copious precipitation of nanometer-sized precipitates take place in the severely-deformed steels.

Effect of Severe Plastic Deformation on the Characteristics of a PM Aluminum Alloy

The paper deals with the influence of severe plastic deformation on the typical powder metallurgy (PM) microstructural characteristics, such as porosity, of a PM aluminum alloy. A commercial ready-to-press aluminum based powder was used as material to be investigated. After applying different compacting pressures (400, 500, 600 and 700 MPa), specimens were debinded in a ventilated furnace at 400 °C for 60 min. Sintering was carried out in a vacuum furnace at 610 °C for 30 min. The specimens were ECAPed for 1 pass. The dimensional and morphological porosity of investigated materials were measured individually for each pore. Results show that ECAP generates shearing stress breaking down the oxide film; this, coupled to particles deformation under local constraints, enables strong bonding and stability. Therefore, ECAP supports next progressive decreasing of pore size as well as strongly influences both dimensional and morphological porosity characteristics, considering that small pores evolve easily to a circular form. Moreover, ECAP cause strong bonding between adjacent particles, which results in a significant increase of mechanical properties.