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Abstract Various methods have been proposed to produce metallic and bulk form materials.Severe plastic deformation, the ways in which you can set quite a lot of mechanical work applied to the metal. Various methods have been proposed to produce metallic and bulk form materials. However, despite the widespread need for tubes with high strength to weight ratio, few studies and attempts have been done to produce ultra-fine and nano structures.Ultra-fine grain metal created by the process have a high resistance by itself. therefore, these can be as high strength steels are used in harmony with the environment. In this study, optimal design of a cast is done in order to increase the homogeneity of the material microstructure and reduce applied force of the pipe production process.Finite element software is used to design the desired format. Since the framework has been designed based on the pressure in angular channels with parallel tube, the channels angles, corners and curved angles, reshaping and the channel radius ratio, the coefficient of friction between the pipe and the channel and the number of passes are the parameters affecting the process.The effect of the above parameters in a homogeneous effective strain rate and force of the process has been studied.

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In this study, the effect of Parallel tubular channel angular pressing (PTCAP) as a severe plastic deformation (SPD) process on the microstructural, mechanical properties and superplasticity of AZ31 magnesium alloy were investigated. PTCAP method at 300°C was performed for production of ultra-fine grained (UFG) tube with a high superplasticity. After the first pass of PTCAP a bimodal microstructure, large gains surrounded by a large number of tiny recrystallized ones, was observed. The grain refinement and homogeneity of the microstructure increased by applying subsequent passes of PTCAP. After four pass of PTCAP, the average grain size of the material decreased from 43 µm to 6.8 µm. Vickers microhardness measurements revealed that by applying more PTCAP passes and consequently, more grain refinement, the value of hardness increased. Fractographic SEM images showed that predominately ductile fracture was occurred in all hot tensile specimens. A higher elongation to failure of 256% was achieved at a higher tensile testing temperature of 450°C and a strain rate of 10-3 1/s, due to grain boundary sliding as a dominant deformation mechanism, while this values for the as-received sample is 116% at the same tensile testing condition. Finally, it was observed that the four-pass PTCAP processed sample has higher room temperature microstructural and mechanical properties and also higher elevated temperature superplasticity than the as-received sample. Also, the grains thermal stability test was done on the four-pass PTCAP processed sample at 5 different temperatures.

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The main goal of this study is achieving thin-walled AZ31 magnesium alloy tubes with high ductility at elevated temperature. For this purpose, a combined severe plastic deformation method, including parallel tubular channel angular pressing (PTCAP) and tube backward extrusion (TBE) was used. First, PTCAP process was applied on tubular samples at 300°C and then, TBE process was performed at 300°C. After PTCAP, a necklace like microstructure, large gains surrounded by a large number of tiny recrystallized ones, was observed and the average grain size of the material decreased from 520 µm to 11.1 µm. At the next stage, After TBE, an ultra-fine grain microstructure with an average grain size of 8.6 µm was formed. After performing this combined method, the hardness value of the PTCAP and TBE processed sample increased from 37 HV to 69 HV. Hot tensile testing studies at 300°C revealed an elongation to failure value of 181% for the PTCAP and TBE processed sample, while this value for as-received sample was 55%. Fractographic SEM images showed that predominately ductile fracture was occurred in all hot tensile specimens due to nucleation of microvoids and their subsequent growth and coalescence with each other.

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The main goal of this study is achieving thin-walled AZ31 magnesium alloy tubes with high ductility at elevated temperature. For this purpose, a combined severe plastic deformation method, including parallel tubular channel angular pressing (PTCAP) and tube backward extrusion (TBE) was used. First, PTCAP process was applied on tubular samples at 300°C and then, TBE process was performed at 300°C. After PTCAP, a necklace like microstructure, large gains surrounded by a large number of tiny recrystallized ones, was observed and the average grain size of the material decreased from 520 µm to 11.1 µm. At the next stage, After TBE, an ultra-fine grain microstructure with an average grain size of 8.6 µm was formed. After performing this combined method, the hardness value of the PTCAP and TBE processed sample increased from 37 HV to 69 HV. Hot tensile testing studies at 300°C revealed an elongation to failure value of 181% for the PTCAP and TBE processed sample, while this value for as-received sample was 55%. Fractographic SEM images showed that predominately ductile fracture was occurred in all hot tensile specimens due to nucleation of microvoids and their subsequent growth and coalescence with each other.