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This work conducted to investigate the effects of accumulative roll bonding (ARB) method on achieving the ultra-fine grain microstructure in AZ31 alloy. Accordingly, a number of ARB routes at 400°C, applying thickness reductions per pass of 35%, 55%, and 85% were performed. The results indicate that both the final grain size and the degree of bonding have been dictated by the thickness reduction per pass. The larger pass reductions promote a higher degree of bonding. Increasing the total strain stimulates the formation of a more homogeneous ultra fine grain microstructure.

Nowadays, Severe Plastic Deformation (SPD) methods are at the focus of material researchers and among these methods, Twist Extrusion (TE) is one of promising ones to pave the way of commercialization. In this Investigation the magnitude of strain distribution along 4 selected paths of sample after 3 passes of Twist Extrusion were investigated by computer simulation and its influence on aluminum 1100 microstructure by experimental tests. ABAQUS 6.5 software based on FEM was applied for the former and 70 mm length samples with cross-section of 18*28 mm were exploited for the latter. According to the simulation results, corner, middle of small side, middle of long side and center of the cross-section are placed from maximum to minimum magnitude of strain respectively. Theses achievements were verified with metallographic images in aspect of metal flow and grain size as well.

Let $D$ be an integral domain with quotient field $K,$ throughout$.$ Call two elements $x,y\in D\setminus \{0\}$$v$-coprime if $xD\cap yD=xyD.$ Call a nonzero non-unit $r$ of an integral domain $D$ rigid if for all $x,y|r$ we have $x|y$ or $y|x.$ Also, call $D$ semirigid if every nonzero non-unit of $D$ is expressible as a finite product of rigid elements. We show that a semirigid domain $D$ is a GCD domain if and only if $D$ satisfies $\ast :$ product of every pair of non-$v$-coprime rigid elements is again rigid. Next, call $a\in D$ a valuation element if $aV\cap D=aD$ for some valuation ring $V$ with $D\subseteq V\subseteq K$ and call $D$ a VFD if every nonzero non-unit of $D$ is a finite product of valuation elements. It turns out that a valuation element is what we call a packed element: a rigid element $r$ all of whose powers are rigid and $\sqrt{rD}$ is a prime ideal. Calling $D$ a semi-packed domain (SPD) if every nonzero non-unit of $D$ is a finite product of packed elements, we study SPDs and explore situations in which a variant of an SPD is a semirigid GCD domain.

A new noble severe plastic deformation method, called accumulative back extrusion (ABE), was developed to assist generating ultra fine grain materials. In the present work the ABE process was successfully applied on AZ31 magnesium alloy up to three passes without any danger of cracks. The results showed that a large shear deformation may introduce through step one, where extensive shear banding and twinning are present in the microstructure. As the second step proceeds via constrained compressive deformation, more deformation inhomogenieties, which may act as preferred nucleation sites for new grains, were introduced in the microstructure. By increasing the number of passes to 3, more homogeneous microstructure with no significant smaller grain size was formed. The strain induced twinning and strain localization, which were led to occurrence of dynamic recrystallization (DRX), were found to be the main reasons of grain refinement during ABE process.