Since tubes are widely used for different industrial applications, processing of tubes by the Severe Plastic Deformation (SPD) method has been the target of different attempts. Among these attempts, development of SPD processes for tubes based on Equal Channel Angular Pressing (ECAP) has been more successful. As an illustration, Tube Channel Pressing (TCP) has been presented as an attractive SPD process since a relatively homogenous strain can be imposed on different sizes of tubes by this process. However, since die/mandrel geometry has a remarkable effect on the Deformation behavior of tube in this process, more efforts must be focused on the optimization of the geometry of this process. This work is aimed to examine a new die geometry for TCP in order to reduce the strain heterogeneity and rupture risk of tube through the process. For this purpose, the effects of different geometrical parameters on the Deformation behavior of tube during the process are studied using FEM simulations. In these simulations, the rupture risk of tube is considered using a damage criterion and then, results of simulations are compared with experiments. Results show that the new geometry of TCP imposes more intense strain, causes less strain heterogeneity and results in less risk of rupture of tube during the process. In addition, comparison of simulations and experiments shows that the applied simulation method can predict the rupture of tube during TCP. Besides this, different geometrical parameters of the new geometry of TCP are optimized by simulations considering dimensions of tube.

Over the last 20-30 years, Severe Plastic Deformation (SPD) technologies have caused a significant resonance in the production of ultrafine grained and nanostructured materials. However, the growth of demand for such technologies is largely limited by the high cost of making products from such materials due to the high energy and labour intensity of their production. Therefore, this article analyzes modern technologies for the production of ultra-fine grained metals and alloys with high strength and ductility, using relatively simple and inexpensive equipment and with minimal time required for their production. The development and proliferation of continuous casting machines in the second half of the 20th century led to the development of many continuous press methods used for Deformation of long billets, among which Conform, Extrolling, Linex and combined rolling-press technologies stand out. Therefore, in the present article all combined and continuous processes currently available for the production of long products with ultrafine grains and nanostructures will be considered. Such structures are fundamentally different from conventional materials, because they combine high strength properties with high ductility. This is relevant for applications where weight, size or special performance characteristics of the parts are important.

High-pressure torsion (HPT) is a metal processing method in which the sample is subjected to a very high Plastic shear Deformation. This process can produce exceptional levels of grain refinement, and provides a corresponding improvement in mechanical properties. To investigate the stress and strain distribution due to HPT process finite element simulation were conducted to investigate effective parameters. The simulation results demonstrate that the lowest effective strain obtained in the centers of the disk and the highest at the edges. Also, the mean stress varies linearly from the center of the disk to the edge region. The compressive stresses are higher in the disk centers and lower at the edges. By increasing the friction coefficient and the die angle, mean stress decrease and stress variation along the disc diameters become more homogeneous.Increasing of the pressure load leads to increase the mean stress and its heterogeneity along the disc radius.

The mechanical properties and thermal stability are the main concerns for the commercial application of Severe Plastic deformed (SPD) metals. Microstructure of a material controls its final mechanical properties. The thermal stability of a microstructure can be defined as the resistance to the restoration processes of recovery and recrystallization. These thermally activated processes are two major phenomena which control microstructure evolution and restore the deformed microstructure. In this investigation, static recrystallization kinetics of copper, Severely deformed by a novel SPD technique, known as simple shear extrusion (SSE), was studied. The micro hardness and microstructure of the deformed samples with different strains annealed at temperature range of 180oC to 290oC were analyzed. Softening fractions calculation at different times and temperatures resulted in investigation of JMAK equation constants. As a result, as the strain increases from 1.15 to 6.9 crystal size and thermal stability decrease, and also time for 50% recrystallization of the material at 210oC which is 864s for the first pass decrease to 299 and 207s for the second and sixth pass, respectively.

In this study, the evolution of parallel tubular channel angular pressing (PTCAP) as a Severe Plastic Deformation process on the hot Deformation behavior of the extruded AZ31 magnesium tube was investigated. After four passes, a more refined and homogeneous microstructure was achieved. To understand constitutive behavior, hot tensile tests were carried out on four passes of specimens at temperatures of 350, 400, and 450º C with strain rates of 0. 0001, 0. 001, and 0. 01 s-1. The dependence of flow stress on strain rate and temperature was investigated by the Zener-Hollomon equation and the activation energy was found to be around 131. 26 kJ/mol. Effect of strain was included in the constitutive equation by applying material constants. Based on the constitutive model, the stress-strain curves of PTCAP processed tubes were extracted and compared with the experimental curves. The results indicate good agreement between experimental and predicted flow curves by considering the softening effect.

Severe Plastic Deformation (SPD) methods were developed for producing of metals and alloys with ultrafine grained (UFG) microstructures having high strength. Parallel tabular channel angular pressing (PTCAP) as a noble Severe Plastic Deformation (SPD) method was used to produce ultrafine grained (UFG) and nanostructured Cu-30%Zn tubes. In this paper, the effect of PTCAP process temperature on the Deformation microstructures and mechanical properties were investigated using experimental tests. Optical microscopy (OM) and scanning electron microscopy (SEM) were used to evaluate microstructural evolutions and fractured surface analysis. Micro hardness and tensile tests were employed to mechanically characterize the PTCAP processed samples. The results showed the strength and the hardness decrease with increasing process temperature up to 100oc, but at 200oc, strength and hardness increase in comparison to that in 100oc. The rise in the strength and hardness of the sample processed at 200oc compared to that at 100oc is because of the partial recrystallization, forming new fine grains with high angle boundaries and twin boundaries. Twinning is dominant Deformation mechanism of brass material in order to low stacking fault energy (SFE).Observations revealed that the failure mode in PTCAPed brass was a ductile rupture with the existence of deep dimples. It also indicates that the temperature has no obvious effect on the fracture mood.

In this work, tendencies of pure Niobium, Fe-20Cr stainless steel, and Ti-36Nb-2Ta-3Zr to formation of micro shear bands inside their microstructures during Severe Plastic Deformation are compared with their mechanical properties. For this purpose, strain hardening behavior and strain rate sensitivity of flow stress of these alloys were measured using tension tests and nano-indentation tests, respectively. Microstructures of the alloys were studied using electron backscattering diffraction method before and after imposition of Severe Plastic Deformation. Results show that increase of the strain hardening exponent and/or strain rate sensitivity of flow stress causes decrease of tendency to formation of micro shear bands during Deformation. Moreover, formation of micro shear bands can be approximately predicted using a parameter previously proposed for prediction of formation of macro shear bands.

A review on the microstructural evolution in magnesium alloys during Severe Plastic Deformation was presented. The challenges deserved to achieve ultrafine/ nanostructured magnesium were discussed. The characteristics of the processed materials are influenced by three main factors, including i) difficult processing at low temperatures, ii) high temperature processing and the occurrence of dynamic recrystallization and grain growth processes, and iii) a combined effect of grain refinement and crystallographic texture changes. Reviewing the published results indicate that there are two potential difficulties with Severe Deformation of magnesium alloys. First, it is very hard to achieve homogeneous ultrafined microstructure with initial coarse grains. The second is the dependency of microstructure development on the initial grain size and on the imposed strain level. It was clarified that different grain refining mechanisms may be contributed along the course of multi-pass Severe Deformation. It was clarified that discontinuous recrystallization takes places during the first stages of Deformation, whereas continuous refinement of the recrystallized grain may be realized at consecutive passes. Shear band formation as well as twinning were demonstrated to play a significant role in grain refinement of magnesium alloy. Also, the higher the processing temperature employed the more homogeneous microstructure may be achieved with higher share of low angle grain boundaries.