Abstract: Equal Channel Angular Extrusion is a widely adopted severe plastic deformation process capable of
imparting large amounts of strain in a material via multiple passes through the die. In order to
facilitate reinsertion of worked bars for multipass processing, reshaping is often required. Although
this topic is rarely discussed in the literature, it is a significant step that can influence processing
efficiency. This paper presents several reshaping options and makes recommendations for method
selection based on the authors’ experiences with each.
Abstract: Linear flow splitting is a new continuous cold forming process where the edge of a sheet
metal is formed into two flanges by splitting and supporting rolls. Thus the production of bifurcated
profiles from sheet metal without lamination of material becomes feasible. The production of such
structures takes place incrementally in a modified roll forming machine. Experimental investigateons
on a HSLA steel show, that even at a surface increase of the sheet edge of about 1800% no
cracks were nucleated in the profiles. EBSD measurements in the splitting centre reveal that similar
to other SPD processes UFG microstructures develop in the processing zone. Thus a steady state is
reached in the processing zone where increasing strain has no more (or little) influence on the
materials properties i.e. its deformability, as it is typical for SPD-processes. The formation of UFG
microstructures is considered to be a mandatory condition for the linear flow splitting process, as it
improves the formability of the material to the extremely high level required for this process. The
mechanical properties of profiles produced by linear flow splitting are characterised by large
gradients, depending on the local deformation and the resulting microstructure. Very high hardness
is measured at the former processing zone, i.e. the splitting centre and the flange surface, where
severe plastic deformation takes place and UFG microstructures are present. In direction to lower
deformation i.e. with increasing distance to the splitting ground or flange surface the hardness
decreases close to the level of the undeformed material. In the present paper the linear flow splitting
process is introduced and the microstructural development in the process zone is discussed on the
base of EBSD measurements on profiles of the steel ZStE 500. The repartition of mechanical
properties in a bifurcated profile is demonstrated by detailed hardness measurements.
Abstract: Relatively high mechanical strength and simultaneously good plasticity of a crystalline
material are determined by the state of its internal structure, preferably nano- or ultra-fine grained
one. To achieve the above combination of properties, various manners of plastic deformation and
heat treatment are applied in practice. One of the most effective processes in this field is severely
plastic deformation, e.g. by the method of equal angular channel pressing (ECAP). During the
ECAP, favourable effects of grain fragmentation and the formation of specific orientation relations
can be attenuated by the process of structure recovery, especially, when the real temperature of
angular extrusion is elevated for physical or technological reasons.
An attempt to modify the ECAP technology was considered, to avoid the unfavourable temperature
effects and to increase at the same time the efficiency of manufacturing the ultra-fine structure of
material. Extrusion of dual-material (AZ31 + Al) ingot was performed at room temperature. As it
seems, the well known difficulties with plastic deformation of materials with hexagonal lattice
symmetry, like AZ31 alloy, have been decreased.
Both experimental and methodological aspects of the angular extrusion of the dual-material ingot
and chosen microstructure characteristics (texture, stress, morphology) are presented. On the basis
of the suggested modification, the text discusses an explanation of physical origins of the
microstructure evolution in the investigated material revealed by experiments.
Abstract: A new technique of continuous severe plastic deformation (SPD)-processing, i.e. ECAP (equal
channel angular pressing)-Conform is applied for the first time to produce long-length rods of
commercial purity Ti with ultrafine-grained structure. The paper reports on the results of
investigation of the microstructure and mechanical properties of Ti rods processed by ECAPConform
and the following wire drawing.
Abstract: The method for production of a structure with a grain size of 30-40 nm in two-phase
titanium alloys is proposed. It is shown, that the nanostructure can be formed in billets of
150×70×15 mm, and sheets of 250×150×1 mm. The method consists of several steps including
hydrogen alloying of the alloy, heat treatment, warm deformation and finally dehydrogenating
α-, α+β and β-titanium alloys have been investigated. Hydrogen content varied in the range 0.1–
30 at. %. Microstructure was examined using optical, scanning, transmission electron microscopy
and X-ray analysis after every step of the treatment.
The investigations have shown that a specific character of phase transformations in hydrogenated
titanium alloys plays a leading role in formation of nanostructure. The effect of dissolved hydrogen
on dynamic recrystallization in α- and β- phases is of a secondary importance. Additional
refinement in structure is observed in the deformed alloys after vacuum annealing, if its temperature
is less than the temperature of their deformation.
The work was focused on the optimization of hydrogen content and deformation conditions with
the aim to create the nanostructure in titanium alloys and to enhance their mechanical properties.
Abstract: Back pressure equal channel angular (BP-ECA) processing was utilised to consolidate a
dehydrided (DH) Ti powder of high interstitial content (1.15 wt.% O, 0.09 wt.% N) at 630°C into
fully dense bulk ultrafine-grained (UFG) Ti. The consolidated samples showed an increase in the
contents of oxygen (1.34 wt.%) and nitrogen (0.3 wt.%). The measured densities of 4.53 g/cm3 for
the consolidated samples after 1 and 3 passes were very close to the theoretical value of pure Ti.
TEM revealed the formation of a bimodal microstructure in the one-pass sample, comprising
equiaxed grains of several micrometers in size with ultrafine grains of the order of 100 nm
uniformly distributed at the triple grain junctions. Most grains had high-angle grain boundaries with
some boundaries exhibiting non-equilibrium characteristics. Upon further BP-ECA processing to
three passes, the micrometer-sized grains were refined down to the ultrafine level and copious
nanoscale deformation twins were introduced by severe plastic strain into those ultrafine grains of
the order of 100 nm. As a result of high interstitial contents and refined grains, the sample after
processing for 3 passes exhibited remarkably enhanced true yield and ultimate strengths of 1510
and 2050 MPa, respectively. Significantly, a noticeable compressive ductility was simultaneously
attained despite such a high interstitial content, thanks probably to the non-equilibrium grain
boundaries, bimodal grain structure and the occurrence of deformation twinning.
Abstract: The microstructure and mechanical properties of nano-crystalline 2219 Al alloy (Al-6.4Cu-0.29Mn,
all in wt %) was studied. Nanocrystalline powders were produced from gas atomized 2219 Al alloy
powders by high energy ball milling at room temperature. Powders were collected at different
milling times and X-ray diffraction (XRD) analysis was used to evaluate grain size. High Vickers
hardness (250HV), high compressive strength (920 MPa) and low ductility (2%) were observed in
unimodal bulk nanostructured 2219 Al alloys consolidated to 99% density by hot pressing (HP). In
addition, these nanocrystalline powders were blended with 15, 30 and 50% of (gas atomized)
coarse-grained powders to obtain balanced mechanical properties of enhanced yield and ultimate
strength and reasonable ductility and toughness as compared to either conventional or
nanocrystalline 2219 alloys.
Abstract: Microstructures of Fe-Cr-Ni and Fe-Mn alloys subjected to severe plastic deformation
under pressure have been studied by high pressure torsion and twist extrusion. This processes have
similar deformation schemes, but very different pressure levels. The paper shows that this has a
dramatic effect on the value of the residual high pressure e-phase in Fe-Mn alloys that underwent
severe plastic deformation using these methods. Under roughly the same equivalent deformation of
5-6 units, the value of the residual e-phase in HPT with 20 GPa pressure reaches 100%. In TE with
1.5 GPa, it does not exceed 50%.
Abstract: Batch severe plastic deformation (SPD) processes are mainly used for laboratory
purposes. More industrially oriented are continuous processes among which the new SPD process
of Incremental Equal Channel Angular Pressing (I-ECAP) is an attractive option. This paper
investigates the feasibility of using I-ECAP for nanostructuring of plates rather than bars. First, a
3D finite element simulation has been performed which shows the importance of restricting
material flow in the direction of plate width. A laboratory rig has been designed, which converts the
vertical movement of the machine crosshead into an oblique movement of the reciprocating punch.
Preliminary trials of I-ECAP have been carried out on a 4x30x100mm Al 1070 plate. Metallurgical
samples after 4 and 8 passes of I-ECAP (route A) have been investigated using TEM. In conclusion,
the new SPD process of I-ECAP is capable of processing plates, which opens up new possibilities
of nanostructuring metals on an industrial scale.
Abstract: Bulk magnesium was consolidated from pure Mg particles with an average size of ~59
µm by back pressure equal channel angular pressing. The Mg powder was processed at 200°C for 4
and 8 passes, respectively, using route C. The consolidated materials displayed density of 1.78
g/cm3, compared to the theoretical value of 1.74 g/cm3 for pure Mg. Vickers microhardness (HV)
values were measured to be about 54. Compressive tests at room temperature revealed yield
strengths of 100-110 MPa and ultimate strengths of up to 142 MPa with strains to fracture of ~9%,
comparable to those for extruded pure Mg. Microstructures were examined using optical
microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy