**4. Improved processing routes for ECAP with magnesium alloys**

The processing routes influenced the final structure of the grain, failure of billet, and shear localization effect through the grain structure size distribution and refinement mechanism of the magnesium and its alloys. The formation of the shear bands is due to the concentration of the thin layer which belongs to the newly formed grains along with the existing grain boundaries. This shear concentration occurs in a layer due to the nearby regions shear, and it develops damage pile; thus, the failure in the billet takes place. The rise in the initial grain coarse volume leads to the rise in the shear amount, which is in the shear band. The possibilities of the localization of the shear are higher, which is shown in the first row of **Figure 1** successively the growth shown in below rows. This decision is in Correspond with the failure of the coarse grain structure in the magnesium and its alloys.

To rectify the issues in the ECAP process of the magnesium and its alloys, some measures have been improvised and designed such as the processing route along with temperature, die angle and the back pressure range and its usage. To bring down the tenor for shear localization the grain cores along with the boundary extents have to reduce. Thus a primary step of extrusion is made to refine the microstructure which can change the initial grain structure as illustrated as **Figure 1** an into refined grain structure like **Figure 1g** or **j**. As shown in the second row of **Figure 1a**, the grain refinement sequence of the newly formed grains can alter through the rise in the processing temperature. This alteration in the ECAP process

**Figure 4.** *Grain structure at the end of the deformation zone [37].*

can provide a huge volume of formed grains and reduced tenor for localization of shear [14, 24–27, 29]. The accumulation of the damage and the shear bands strain have reduced through the increase in the die angel during the ECAP process. The billet cracking which normally caused by the damage accumulation and the additional grain refinement can achieve by using the back-pressure during the ECAP process of the magnesium alloys.

An alternate method is by subjecting the magnesium alloys to the multiple ECAP as initial pas in the elevated temperature, and the sequent passes in lower temperature can help to achieve a fine-grain structure with the homogeneous distribution. This process resembles the technique which follows the extrusion process before the ECAP [31].

The customizing of the grain size distribution in the magnesium alloys is associated with the grain structure refinement mechanism of the alloys, which processed through the ECAP process. By changing the ECAP process, it is desirable to alter or control the grain structure and its fine or coarse refinement structure. To increase the certain mechanical properties of the material such as ductility and strength concept of manipulating the material grain boundary and grain refinement was introduced many years ago in the basis of the grain boundary engineering, the same concept have been followed and approached in the process of ECAP. The recent investigations showed that through the ECAP process, the alteration of the grains structure and its distribution achieved in the selected materials. This merit region in the process mentioned above is, for instance, developing a grain distribution in the bimodal configuration in nanostructured Cu, a combination of enhanced ductility and sufficient strength showed up during the tensile testing at ambient temperature which presented in research work. To obtain the sufficient strength and altered elongated grains to increase the stability during the tensile deformation, ECAP method paves the way for these through the forming ultrafine grains and altering the grain size distribution. Among the Grain size distribution, the bimodal configuration considered as the efficient thing for rising the ductility characteristics during the cyclic loading and deformation which assure mechanical properties can improve through the grain size engineering [23–27].

### **5. Effect of texture**

The influence of texture is not straightly integrated with any developed model for the refinement of the grain structure. Unless the developed modal is expected to be effective for ECAP processing route and initial texture. This typical thing

**39**

*Severely Plastic Deformed Magnesium Based Alloys DOI: http://dx.doi.org/10.5772/intechopen.88778*

achieve the deformation.

supposed due to the forming mechanism of the grain structure along with the grain boundaries has witnessed in the magnesium and its alloys which are having the distinctive initial structures while processing in the various temperature range where ECAP is typically carried out [17]. With the uniform procedure, a recent research work analyzed the texture of magnesium AZ31 which processed through the rolling process and ECAP process and they concluded that texture did not influence the size of the grain which formed after the process meanwhile texture influences the chance of formation of new grains and deformation amount which needed to

With the recent proposed modal of ECAP, the progression in the structure of the grain refinement mechanism is witnessed [29]. The bimodal distribution of grain structure observed due to the fine grain refinement and grain nucleate around the boundaries of the groan and twins in the presence of area which does not get affected by the process. A research work [8] provides a technique in which grain which subjected to the recrystallization is nucleate throughout the existing grains in the materials and progress until the structure reaches the homogenous structure equiaxial. The variation among the grain structure refinement modal relies upon the region of nucleation, which tends to form the new grain and feasibility of forming the heterogeneous distribution of grains. Some research delivered that

Because of the coarse grains at the initial stage, the predicted criteria from the developed grain refinement model is getting disapproved with the homogeneous distribution of grain sizes. Possibly grain growth and altered grain structure had observed in the material after subjecting it to the complete ECAP process. In the different stages of the grain refinement, fine grains get nucleated throughout the existing grains and in the region of twin boundaries which happened as expected by the grain structure refinement modal which leads to the distribution of grain size in a heterogeneous manner. The temperature for the intermediate process is likely to prevent the growth of grain and influenced the grain structure to form the bimodal

The maximum tensile strength is recorded through the compressive tests and in various ways as possible for the material which subjected for three passes of ECAP process which given in **Figure 5**. The data of the received material included for better understanding [30]. It witnessed that the ECAP processed specimen shows elevated flow stress in multiple directions when compared with processed ones. The material which undergone the ECAP process display an improved yield and maximum yield stress along with improved behavior in the work hardening towards the different compression direction. Significantly the ECAP processed material which tested along the direction of the Y-axis which is perpendicular to the die channel of the ECAP setup shows a concave up like feature with the strain range of 0.02–0.05. Another major witness is that processed sample demonstrates a constant hardening strain range from 0.01 to 0.03 towards the direction of Z-axis and in the direction of X axis it shows 0.01–0.06 in which the hardening rate is slightly get decreased from the initial stage. The processed material showed up a rise in harden-

From the above results, it is clear that ECAP processing ensures the mechanical anisotropy behavior of the commercially pure Magnesium. The appearance of twinning action in the material during the compression test leads to the anisotropy. The incident of increased hardening rate is clearly because of the twinning action

heterogeneous grain size distribution in the magnesium and its alloys.

distribution, which witnessed after the ECAP process.

ing rate in the range of 0.015–0.3045 in the direction of Y-axis.

**6. Effect of mechanical behavior**

#### *Severely Plastic Deformed Magnesium Based Alloys DOI: http://dx.doi.org/10.5772/intechopen.88778*

*Magnesium - The Wonder Element for Engineering/Biomedical Applications*

can provide a huge volume of formed grains and reduced tenor for localization of shear [14, 24–27, 29]. The accumulation of the damage and the shear bands strain have reduced through the increase in the die angel during the ECAP process. The billet cracking which normally caused by the damage accumulation and the additional grain refinement can achieve by using the back-pressure during the ECAP

An alternate method is by subjecting the magnesium alloys to the multiple ECAP as initial pas in the elevated temperature, and the sequent passes in lower temperature can help to achieve a fine-grain structure with the homogeneous distribution. This process resembles the technique which follows the extrusion process before the

The customizing of the grain size distribution in the magnesium alloys is associated with the grain structure refinement mechanism of the alloys, which processed through the ECAP process. By changing the ECAP process, it is desirable to alter or control the grain structure and its fine or coarse refinement structure. To increase the certain mechanical properties of the material such as ductility and strength concept of manipulating the material grain boundary and grain refinement was introduced many years ago in the basis of the grain boundary engineering, the same concept have been followed and approached in the process of ECAP. The recent investigations showed that through the ECAP process, the alteration of the grains structure and its distribution achieved in the selected materials. This merit region in the process mentioned above is, for instance, developing a grain distribution in the bimodal configuration in nanostructured Cu, a combination of enhanced ductility and sufficient strength showed up during the tensile testing at ambient temperature which presented in research work. To obtain the sufficient strength and altered elongated grains to increase the stability during the tensile deformation, ECAP method paves the way for these through the forming ultrafine grains and altering the grain size distribution. Among the Grain size distribution, the bimodal configuration considered as the efficient thing for rising the ductility characteristics during the cyclic loading and deformation which assure mechanical properties can improve

The influence of texture is not straightly integrated with any developed model for the refinement of the grain structure. Unless the developed modal is expected to be effective for ECAP processing route and initial texture. This typical thing

process of the magnesium alloys.

*Grain structure at the end of the deformation zone [37].*

through the grain size engineering [23–27].

**5. Effect of texture**

ECAP [31].

**Figure 4.**

**38**

supposed due to the forming mechanism of the grain structure along with the grain boundaries has witnessed in the magnesium and its alloys which are having the distinctive initial structures while processing in the various temperature range where ECAP is typically carried out [17]. With the uniform procedure, a recent research work analyzed the texture of magnesium AZ31 which processed through the rolling process and ECAP process and they concluded that texture did not influence the size of the grain which formed after the process meanwhile texture influences the chance of formation of new grains and deformation amount which needed to achieve the deformation.

With the recent proposed modal of ECAP, the progression in the structure of the grain refinement mechanism is witnessed [29]. The bimodal distribution of grain structure observed due to the fine grain refinement and grain nucleate around the boundaries of the groan and twins in the presence of area which does not get affected by the process. A research work [8] provides a technique in which grain which subjected to the recrystallization is nucleate throughout the existing grains in the materials and progress until the structure reaches the homogenous structure equiaxial. The variation among the grain structure refinement modal relies upon the region of nucleation, which tends to form the new grain and feasibility of forming the heterogeneous distribution of grains. Some research delivered that heterogeneous grain size distribution in the magnesium and its alloys.

Because of the coarse grains at the initial stage, the predicted criteria from the developed grain refinement model is getting disapproved with the homogeneous distribution of grain sizes. Possibly grain growth and altered grain structure had observed in the material after subjecting it to the complete ECAP process. In the different stages of the grain refinement, fine grains get nucleated throughout the existing grains and in the region of twin boundaries which happened as expected by the grain structure refinement modal which leads to the distribution of grain size in a heterogeneous manner. The temperature for the intermediate process is likely to prevent the growth of grain and influenced the grain structure to form the bimodal distribution, which witnessed after the ECAP process.
