Magnesium is one of the lightest stuffs among all alkalic Earth metals. They are more attractive as structural stuff used in many applications such as Aerospace industries, automotive industries, stuff ‘s handling, transit industries and electronic industries ( B.L. Mordike et.al. ( 2001 ) , R.Ye. Lapovok et.al. ( 2004 ) , Mustafa Kemal Kulekci ( 2008 ) ) . Because of many advantages of Mg, that is low denseness, first-class muffling capacities, really good recycling capacities, good machinability ( T.S. Srivatsan et.al. ( 2008 ) , Yuichi Miyahara et.al. ( 2006 ) ) , and besides characterized by high specific strength, stiffness, high electromagnetic shielding and good thermal or electrical conduction at elevated temperatures ( JIANG Ju-fu et.al. ( 2010 ) ) . Even though Mg metals have many advantages, they have few restrictions in industrial applications at atmospheric temperatures, because of low strength, hapless formability, and hexagonal closed battalion ( HCP ) construction with the lower limit faux pas system, which leads to hapless ductileness ( Manuel Marya et.al. ( 2006 ) ) . In order to get the better of these restrictions few decennaries ago many research workers have developed conventional and multi-pass bulge processes for enforcing the big strain in the stuffs but these procedures did non accomplish up to the degrees which are used in the industrial applications ( A. Azushima et.al. ( 2008 ) ) . After extended probes, research workers used terrible fictile distortion ( SPD ) techniques to enforce the big plastic strain in the stuff by manufacturing the majority metals to make into ultrafine grained metals ( R.Z. Valiev et.al. ( 2000 ) , Y. Iwahashi et.al. ( 1997, 1998 ) ) .
So to supply the best consequences, one of the interesting SPD techniques is Equal Channel Angular Pressing and besides known as Equal Channel Angular Extrusion ( V.M. Segal ( 1995, 2002 ) , L. Olejnik et.al. ( 2005 ) ) . It was developed among all the techniques such as Accumulative Back Extrusion ( S.M. Fatemi-Varzaneh et.al. ( 2009, 2010 ) ) , Cyclic Extrusion Compression ( Y.J. Chen et.al. ( 2008 ) , Qudong Wanga et.al. ( 2010 ) ) , Accumulative axial rotation Bonding ( J.A. del Valle et.al. ( 2005 ) , ZHAN Mei-yan et.al. ( 2008 ) ) , Friction splash processing ( B.M. Darras et.al. ( 2007 ) , DU Xing-hao et.al. ( 2008 ) , ZHANG Da-tong et.al. ( 2011 ) ) , High Pressure Torsion ( Genki Sakai et.al. ( 2005 ) ) , Twist bulge ( Y. Beygelzimer et.al. ( 2009a, 2009b ) , M.I. Latypov et.al. ( 2012 ) ) , Reciprocating bulge ( Shih-Wei Lee et, Al. ( 2007 ) , Jien-Wei Yeh et.al. ( 1998 ) , YANG Wen-peng et.al. ( 2012 ) ) , Insistent corrugation and strengthening ( V. Rajinikanth et.al. ( 2008 ) , S.C. Pandey et.al. ( 2012 ) ) , Severe tortuosity straining ( Katsuaki Nakamura et.al. ( 2004 ) ) , Cylinder covered compaction ( X. Zhao et.al. ( 2004 ) , ZHAO Xin et.al. ( 2007 ) ) , Submerged clash splash processing ( Douglas C. Hofmann et.al. ( 2005 ) ) , Constrained channel pressure ( Dong Hyuk Shin et.al. ( 2002 ) , F. Khakbaz et.al. ( 2012 ) ) and Insistent upsetting ( W. Guo et.al. ( 2012 ) ) .The purpose of ECAP technique is to obtain effectual mechanical belongingss and microstructures in nanometer graduated table of the stuff. By polishing the majority stuffs in ECAP at disconnected dice angle, without any alterations in form of the stuff, big plastic strain was imposed and concluded the mean grain size was less than a micron. It was clearly explained by the undermentioned Hall-Petch equation ( Ruslan Z. Valiev et.al. ( 2006 ) ) :
…………………….. ( 1 )
Where K is a changeless value, ?o is a clash emphasis, ? is a output emphasis and vitamin D is a grain size of the stuff.
Chiefly, ECAP is developed for few advantages as compared to other techniques. First, it has a simple process to enforce the plastic strain in the stuff at a shear zone where the shear distortion is occurred. Second, the size of the grains in the stuff is decreased by increasing the figure of base on ballss so that output strength of the stuff can better. Third, it is a best method to better the mechanical belongingss of the stuff at any conditions ( hot working and cold working procedures ) . Fourth, the flexibleness ( crystal construction ) of the stuff improves efficaciously in the ECAP procedure. Overall, the ECAP procedure is a valuable technique among all the SPD techniques.
Wrought Mg metals
Wrought metals are available in assorted forms as bars, sheets and metal bars as compared to project Mg metals ( metal bars merely ) , as illustrated in Fig.1 ( a ) ( Horst E. et.al. ( 2006 ) ) . In this, the major per centum of Mg stuff combined with minor per centum of other metals such as an Aluminum, Zinc and Manganese for altering their belongingss, usually called as metal. Particularly AZ ( Aluminum and Zinc ) wrought Mg metals have more industrial application as compared to aluminum metals. Therefore, AZ wrought Mg metals are used to augment the strength required for stuff who is addition with the addition in Al ‘s content.
Harmonizing to ASM enchiridion ( 1992 ) , the composings and their mechanical belongingss of the AZ wrought Mg metals are illustrated in the Table.1. The AZ31B metals are chiefly used in cathodic protection due to their medium strength with formability, but in instance of AZ31C is a lower-purity commercial fluctuation of AZ31B used where the minimal corrosion opposition in light weight applications. The AZ61 metal has high strength than AZ31 metal, and it has a high corrosion opposition as high-purity metal. The highest strength metal in the AZ metal is AZ80 metal, and it can be unnaturally aged for extra strength.
This reappraisal paper has explained elaborate overview of assorted rules, which are developed in ECAP procedures. Furthermore, it has described the current position of the ECAP procedure was used as a processing tool for the fiction of bulk metals to make into ultrafine grained constructions in the stuff by minimising the figure of base on ballss. This paper reviewed on factors, which are act uponing in ECAP procedure at different parametric quantities and besides this paper reviewed the belongingss ( output strength, Ultimate tensile strength, elongation, hardness ) of this shaped Mg metal at different conditions.
Methodologies of ECAP
Many research workers with new advanced thoughts in the overall universe have done legion alterations and modernisations of different die-set design for ECAP procedure for bettering the shear distortion and belongingss of the stuffs as illustrated in table. 2. Therefore, the basic information about the different dies for ECAP, which was developed by research workers explained clearly as follows.
2.1. Conventional Side Extrusion for ECAP
First, the Segal was proposed ECAP procedure to enforce the big plastic strain in the specimen by refined majority stuffs. Furthermore, the grain size of the stuff has to be reduced extensively for bettering the mechanical belongingss. The rule of ECAP is schematically outlined in Fig. 2. In this procedure, a sample was pressed through ECAP dice to enforce the big plastic strain in majority stuffs to make an ultra-fine grain micro-structure or bomber micron constructions. The ECAP dice channel was set at regular angle called as dice angle ( ? ) usually taken as 90 deg. ( see in table 5 ) and the point at which channels are intersected is called as either outer discharge of curvature ( ? ) or radius ( R ) . Hence the entire strain imposed on the specimen is calculated by utilizing the undermentioned equation ( F. Djavanroodi et.al. ( 2010 ) , Seung Chae Yoon et.al. ( 2008 ) , I. Balasundar et.al. ( 2009 ) , C.J. Luis Perez ( 2004 ) ) . At a individual base on balls, the entire strain of the specimen for this conventional ECAP was acquired by equation ( 2 ) , and the accrued sum strain is n? after ‘n ‘ figure of base on ballss.
? = …………….. ( 2 )
Where ? is entire strain, is die angle, is outer arc curvature.
On other custodies, the ECAP has four basic cardinal paths to material flow procedures during the operation. They are route A, path, path, and path C ( Minoru Furukawa et.al. ( 1998 ) , P. Venkatachalam et.al. ( 2010 ) ) . Where in path A, the samples were pressed without any rotary motions ; in path, the specimen rotated by 90 deg. with clock wise way between back-to-back base on ballss ; in path, the specimen rotated by 90 deg. counter clock wise between back-to-back base on ballss, and specimen rotated by 180 deg. between base on ballss in Route C. From the Table 5, it can be observed that maximal figure of research workers had been used path and they reported that the micro construction of the specimen in Route after 4 base on ballss was same in Route A after 10 base on ballss. But in this dice in every base on balls of ECAP procedure the sample has to be removed, with or without rotary motions ( Ruslan Z. Valiev et.al. ( 2006 ) ) . In order order to avoid these restrictions, many research workers have been developed different processs are like rotary-die ECAP, multi base on balls for ECAP, side bulge procedure for ECAP.
2.2 Rotary-die ECAP
It has a simple rule to increase the fictile strain without taking samples from dice in every back-to-back base on balls by utilizing the rotational method of ECAP procedure. The rule of rotary dice ECAP is schematically outlined in fig.3 ( Aibin Ma, et.al. ( 2005 ) , Y. Nishida, et.al. ( 2002 ) ) . In this, the channels intersect each other with an angle of 90 grades, and the stuff was inserted in dice for imperativeness by speculator in fig. 3 ( a ) . In fig. 3 ( B ) , the specimen was pressed by speculator it means one base on balls has to be finished, and in fig. 3 ( degree Celsius ) the sample was pressed once more after rotated by 90 deg. By utilizing this processes for a individual sample can be pressed up to maximum 32 base on ballss. By observation of fig. 3 ( a ) , Route A was suited for this procedure without any rotary motion. However, the sample is nonuniform due to aspect ratios are little ( Ruslan Z. Valiev et.al. ( 2006 ) ) .
2.3 Side Extrusion with back force per unit area for ECAP
The rule of insistent side bulge for ECAP is schematically outlined in Fig. 4 ( Akira Azushima, et.al. ( 2002 ) ) . It seems to be a rotary-die ECAP procedure but have a different methodological analysis. It consists of four clouts, i.e. clout A, clout B, clout C, and punch D. Punch A and clout B is movable with a changeless velocity and changeless dorsum force per unit area severally. Where, Punch C and Punch D are fixed as shown in fig. 4.
The sample was pressed through the dice in between Punch A and Punch B to enforce the big plastic strain in the specimen obtained 1.15 after one base on balls. So Route A is suited for these procedures every bit same as rotary-die ECAP but the figure of base on ballss increased up to 10passes efficaciously without remotion of the specimen ( Ruslan Z. Valiev et.al. ( 2006 ) ) .
2.4 Multi-Pass Bulge for ECAP
In order to cut down the figure of base on ballss like rotary-die ECAP procedure and insistent side bulge for ECAP procedure research workers have been developed another procedures by increasing the figure of channel angles are schematically outlined in fig. 5 ( Kiyotaka Nakashima, et.al. ( 2000 ) ) . However it has multiple bends to press the stuff through the channel. Hence it is a really effectual method to better mechanical belongingss by cut downing the figure of base on ballss, and they reported the entire strain of the stuff reveal no difference between multi-pass ECAP and standard insistent ECAP procedure in either micro hardness or micro construction rating.
2.5 Parallel channel Bulge for ECAP
The rule of the Parallel channel bulge for ECAP procedure is schematically illustrated in fig. 6 ( G.I. Raab, et.al. ( 2005 ) ) . In this the shear distortion takes topographic point two times by individual operation when a sample was pressed through a parallel channels for obtaining the ultrafine grained metals. Where ‘? ‘ is the angle which intersects at the parallel channel, ‘N ‘ is the shear way and ‘K ‘ is the supplanting between the channels it was about equal to impart diameter ‘dc ‘ as shown in fig 6. The advantage of this procedure is to enforce the entire strain in the stuff is homogenous with the minimal figure of base on ballss.
Equal channel angular turn overing
In order to bring forth continues long metal strips, the Equal channel angular peal ( ECAR ) have been introduced. It is besides called every bit uninterrupted confined strip shearing ( S2C2 ) or Dissimilar-channel angular pressure ( DCAP ) . The rule of ECAR/DCAP/S2C2 is schematically outlined in fig. 7 ( Yong Qi Cheng, et.al. ( 2007, 2008 ) ) . In this procedure, the thin sheet stuff entered in between specially designed rollers ( feeding axial rotation and Guide axial rotation ) which gives power to the specimen to acquire into the ECAP channels ( Channelss are in dissimilar to entry and issue ) for organizing as shown in fig. 7. Here the entry channel at rolled operation and mercantile establishment channel of ECAP thickness was decreased and ‘H ‘ is a channel tallness, ‘? ‘ is an oblique angle and ‘r ‘ is an oblique radius of the ECAR channel.
Con shearing ECAP
The rule of con shearing ECAP is schematically outlined in fig. 8 ( H. Utsunomiya, et.al. ( 2004 ) , Y. Saito, et.al. ( 2000 ) ) . This method was developed for continues and long metallic strip, which is similar to ECAR procedures but here the specimen is fed into the orbiter axial rotations and the cardinal axial rotation which is rotated at the same velocities to acquire a high bulge force so after the specimen entered into the ECAP dice from the axial rotation factory. In this, the entire strain imposed efficaciously because of uninterrupted shear distortion taken topographic point.
Another alternate method for bring forthing the ultrafine grained long metallic bars is ECAP-conform procedure. The rule of conform ECAP is schematically outlined in fig. 9 ( Ruslan Z. Valiev et.al. ( 2006 ) ) . It has a revolving shaft with a channel at the centre of conform installation, and a stationary restraints die. So that the frictional forces are generated at these three contact interfaces ( revolving shaft, stationary constrained dice, channel ) to give a motion of the work stuff into ECAP where it was arranged at issue channel of this conform installation. The forced stationary dice is used to command the work stuff and besides forces to displacement the way to regular ECAP procedure. Therefore, this procedure is utilizing for continues processing of metals ( Cheng Xu, et.al. ( 2010 ) ) .
2.9 Change channel angular pressure ( CCAP )
Tianmo Liu et Al ( 2009 ) , LIU Yu et Al ( 2011 ) , were proposed new technique to make an ultrafine grain in a nanometre scope in the stuff. The rule of Change channel angular Extrusion ( CCAE ) was schematically outlined in fig. 10. It is a combination of ECAE procedure and High bulge ratio procedure. In this, the entire strain imposed in bulk stuff by pressed the sample into two inequalities cross-sectional country crossing channels to make ultrafine grain stuffs and besides to better mechanical belongingss of metals. The chief aim of CCAE procedure is to cut down the grain size by reduces the figure of base on ballss. AZ31 Mg metals have been examined in CCAE procedure, obtained the grains to 15 µm from 500 µm at 523 K ( LIU Yu et Al ( 2011 ) .
2.10 Double alteration channel angular pressure ( DCCAP )
Liwei Lu et Al ( 2012 ) , proposed a new bulge technique is a dual alteration channel angular pressure ( DCCAP ) to polish the grains significantly without any clefts during the shear distortion of AZ31 metals. The rule of Double alteration channel angular pressure ( DCCAP ) is as shown in fig. 11. It has a perpendicular channel same as in the ECAP procedure and besides have two smaller diameter horizontal channels for produce the flexibleness of the stuff. The chief advantage of this procedure is to enforce the big strain for making the UFG micro constructions in the majority metals at even corner points of the sample. It is used as a simple technique and efficaciously to alter the micro structures at the ambient temperatures for HCP metals like Mg metals.
2.11 Tubular Channel angular pressing TCAP
Ghader Faraji et.al. ( 2011, 2012 ) , introduced a new SPD novel technique is Tubular channel angular pressure ( TCAP ) . As illustrated in fig.12, the rule of TCAP procedure has constrained by the inner and outer dies. It has a four level part ( a, B, degree Celsius and vitamin D ) and three shear distortion zones for impose the entire strain in the cannular work piece with extra radial and circumferential tensile and compressive strain in a part B and degree Celsius severally pressed by clout as shown in fig. 12 ( a ) . R and Ri are the radii of the tubing in the channel part and concluding tubing severally as shown in fig. 12 ( B ) .
Research workers have been obtained the tantamount strain of a cannular work pieces was calculated as 2.67, and it was higher than the three base on ballss of ECAP procedure is 1.863. This technique was applied to a commercial AZ91 Mg metal, and a important grain polish was achieved even after individual rhythm TCAP. The micro hardness of the tubing was increased to 78Hv from an initial value of 51 Hv. This new fresh SPD procedure is assuring for future industrial application ‘s, peculiarly cylindrical tubings. The channels are made by either triangular or semicircular forms.
2.12 Parallel cannular channel angular pressure ( PTCAP )
Another new novel SPD procedure is a parallel cannular channel angular pressure ( PTCAP ) was introduced by Ghader Faraji et Al ( 2012 ) , for the bring forthing ultrafine grained and nanostructure tubings. It is a new design of TCAP procedure, and the rule of this procedure is schematically represented as shown in fig. 13.
It consists of two half rhythms. The tube stuff is pressed through two shear zones to make a larger size, and so the stuff is pressed back through the same shear zones to make its initial dimensions at first half and 2nd half rhythms of PTCAP severally. The tantamount plastic strain was calculated in PTCAP is about 3±0.05. The grain size of the tubing is refined from ~59 ?m to 150-300 nanometer and the micro-hardness increased from 61 Hv to about 117 Hv for pure Cu stuff ( Ghader Faraji, et.al. ( 2012 ) ) .
On the other manus, the Equal channel angular drawing ( ECAD ) procedure ( A. Azushima et.al. ( 2008 ) , ( Ruslan Z. Valiev et.al. ( 2006 ) ) , I-shaped equal channel angular pressure ( I-ECAP ) ( A. Azushima et.al. ( 2008 ) ) , and clash reduced ECAP ( A. Azushima et.al. ( 2008 ) ) were proposed by many research workers to make ultrafine grained metals by impose the big plastic distortion in the stuff.
3. Factors of ECAP
The ECAP procedure is a metal forming procedure in which ; the sample was pressed through the dice by utilizing a speculator, to enforce the big plastic strain by simple shear distortion on majority metals to measure the ultrafine grained constructions. However, there are several factors are influenced on extremist mulct grained micro structural features of the as-pressed specimens. Therefore, this paper reviewed the factors which are influenced chiefly while making the operation of ECAP procedure. They are, values of the angles ( die angle ( ? ) and angle of curvature ( ? ) ) of the dice in ECAP procedure, the faux pas systems and shearing forms took topographic point while treating the paths ( A, , and C ) , the ram velocity of pressure, the temperature of the pressure operation, back force per unit area ( with or without ) .
3.1 Die geometry
In order to better the ultrafine grain metals and its micro constructions, the big plastic strain is imposed in metals by pressing the specimen into the dice of ECAP. It means that, the values of the angles within the die Acts of the Apostless as a cardinal function for enforce the big strain in the specimen. In this, the dice angle ( ? ) influenced straight to the entire strain imposed on the specimen was calculated from equation ( 2 ) and reported the consequences in fig. 14. Many research workers have been developed and reported that, the lower limit dice angles and corner angles are produced big tantamount strains for important UFG micro constructions in the stuff ( Ruslan Z. Valiev et.al. ( 2006 ) , Kiyotaka Nakashima et.al. ( 1998 ) ) .
From fig. 14, research workers have been evaluated the sum strain which was decreased when the channel angle is increased from 45 deg. to 180 deg. with the discharge of curvature ranges from zero deg. to 90 deg. for a individual base on balls at N=1 ( Ruslan Z. Valiev et.al. ( 2006 ) ) . However, the corner angles are non affected much as compared to the ? angles except below 90 deg. So that lower angles are given ever better strains for a stuff as compared to higher angles. From table 5, research workers were suggested the lower limit dice angle with minimal discharge of curvature to obtain the UFG construction in the stuff.
However, till the day of the month, there is a small or no effort to make any important comparing between the different channel angles for shaped Mg alloys every bit reported like pure aluminium at different angles as shown in fig. 15. In this they were examined the entire strain values of the specimen at different channel angles by the lower limit of discharge of curvature for Al ‘s stuff ( Ruslan Z. Valiev et.al. ( 2006 ) , Kiyotaka Nakashima et.al. ( 1998 ) ) . Unlike from the above figure, there is a small information described on AZ wrought Mg metals by compare the stuffs at different channel angles with different discharge of curvatures for optimising their consequences ( see table 5 ) .
3.2 Processing Paths in ECAP
There are four basic cardinal processing paths in ECAP procedure was already described in this paper as shown in fig. 16. Research workers have been improved the different micro constructions in assorted shaped Mg metals by utilizing these paths. They obtained important UFG micro constructions in as-pressed samples with path than route A ( see table 5 ) . Furthermore, they have examined the combination of paths at different back-to-back phases and addressed there is no extra net income in micro constructions.
While treating these paths in ECAP procedure, they are associated with the different faux pas systems in different base on ballss at X, Y and Z planes as represented schematically in fig. 17. So that the entire strain in a sample was evaluated in every base on balls through the procedure. Further, when measuring the influence of processing paths consider the shearing system deductions in matching four paths, which are described by took an illustration of 3-dimensional component. So the deformations of paths are introduced into a 3-dimensional component at X, Y and Z planes for eight base on ballss to measure the UFG microstructure as represented in fig. 18 ( Ruslan Z. Valiev et.al. ( 2006 ) ) .
However, from the above observations, research workers have concluded in the undermentioned ways. First, there is no distortion occurred in path Angstrom at Z plane. Second, the component has restored its original form in path and path C at Y plane is in every 2passes, and everyone base on balls severally but in the X plane, the component restored its original form in every 4passes and every back-to-back base on balls in the same two paths severally. Furthermore, the component was deformed efficaciously in the path A and path ( Ruslan Z. Valiev et.al. ( 2006 ) ) .
The specimen pressed through the dice in the ECAP procedure by utilizing random-access memory for polishing the grain size of the specimens. Therefore, the random-access memory velocity besides to be considered as one of the factors act uponing in ECAP procedure. The hydraulic imperativenesss normally used random-access memory velocity is up to 20 mm/sec. In last few decennaries research workers have been examined on the random-access memory velocities from mm/sec to 10 mm/sec. They reported that there is no important influence on the equilibrium size of UFG metals during ECAP because it was influenced by increasing the figure of base on ballss ( Ruslan Z. Valiev et.al. ( 2006 ) ) .
Chin-Sung Chung et.al. ( 2005 ) , proposed the output strength of the AZ31 metal at ram velocity was 5 mm/sec, The values vary 126 MPa, 126 MPa, 152 MPa and 180 MPa for 1, 2, 3and four base on ballss correspondingly. Furthermore, for the same random-access memory velocity was 5mm/sec, the output strength of the AZ61 metal varies 193 MPa, 202 MPa, 208 MPa and 191 MPa for 1, 2, 3 and four base on ballss severally.
So the random-access memory velocity has a minor important influenced factor for grain polish in the specimen. A similar observation was besides made from others, and it was presented in table.5. They reported that the random-access memories velocity may hold increased when the specimen was heated at higher temperatures every bit good as lower velocities are used for lower temperatures.
Temperature of the specimen is another of import factor influencing in the ECAP procedure while treating the shaped Mg alloys because of HCP construction. Yuichi Miyahara et.al. ( 2006 ) , selected the temperatures of 473 K and 523 K for AZ61 metal in Ex-ECAP procedure for refine the grain size of the sample. They improved the size of the grains for these temperatures are around ~0.6 µm and ~1.3 µm severally. M. Janecek et.al. ( 2007 ) , proposed the output emphasis ( MPa ) decreases when the specimen temperature increased as shown in fig. 19.
At room temperatures, the output strength of the AZ31 metal varies from 65 MPa at zero passes to 210 MPa after four base on ballss, but the output emphasis decreased to less than 65 MPa at 573 K. So that the output emphasis of the specimen gives an effectual consequence at room temperature than the elevated temperatures. K. Xia et.al. ( 2005 ) , improved the grain size of the AZ31 metal by treating the ECAP at lower temperatures. They reported the grain size was decreased from ~15-22 µm to ~2 µm at 473 K after eight base on ballss but the grain size significantly reduced to ~1 µm at 423 K. The size of the grains at 373 K reduced between 0.2 µm and 0.5 µm after four base on ballss. Therefore, the lower angle grain boundaries improved by increasing the temperature, but whereas at lower temperatures, the smallest possible equilibrium grain size and the highest fraction of high-angle boundaries have been achieved ( see table 5 ) .
Back force per unit area
Back force per unit area is one of the of import factors in the ECAP procedure for obtaining the UFG structured stuffs. Fig. 20 ( V.V. Stolyarov et.al. ( 2003 ) ) , shows a set-up of ECAP procedure with controlled back force per unit area at typical lading curves. The chief advantage of back force per unit area is used to better the workability of the stuff. To heighten the visibleness in the uniformity of the metal flow during ECAP operation. And besides to better the grain polish by cut downing the figure of base on ballss in the pressed stuff ( K. Xia et.al. ( 2005 ) , Feng Kang et.al. ( 2009 ) , Cheng Xu et.al. ( 2009 ) , R. Lapovok et.al. ( 2008 ) ) .
Majid Al-Maharbi et.al. ( 2011 ) , was reported the consequences to heighten the uniformity shear distortion in the AZ31 metal, with an bulge ratio of 0.075mm/sec at 473 K with the back force per unit area of 30 MPa. X.N. Gu et.al. ( 2011 ) , used multi base on balls ECAP procedure to better the mechanical belongingss of the AZ31 Mg metal with back force per unit area and without back force per unit area. They reported that it had been efficaciously improved the mechanical belongingss of Mg metals with back force per unit area whereas without back force per unit area. In this, the grain size decreased from 28 µm to 8.5 µm after 4passes, besides the output strength, ultimate tensile strength and elongation vary about 150MPa, 230 MPa and 16.5 % severally whereas without back force per unit area the YS, UTS and elongation vary about 105 MPa, 280 MPa and 31 % severally. Finally, they have decreased the mean grain size about 1.7MPa and besides the YS, UTS, Elongation values was improved about 285 MPa, 430 MPa, and 31 % severally.
Jizhong Li et.al. ( 2011 ) , proposed the consequences with same multi-pass ECAP procedure with the back force per unit area was the mean grain size ( 0.8 µm ) by polishing the coarse grained ( 980 µm ) for pure Mg metal bar at room temperature. Furthermore, it is a sensible to expect from earlier consequences that the presence of back force per unit area will take to important extra grain polish but really few consequences are available to day of the month for measuring the consequence of back force per unit area on the ability to accomplish homogeneousness in the Mg AZ wrought metals.