In this study, annealed pure copper was extruded using equal channel angular extrusion （ECAE） for a maximum of eight passes. The fatigue resistance of extruded specimens was evaluated for different passes and applie...In this study, annealed pure copper was extruded using equal channel angular extrusion （ECAE） for a maximum of eight passes. The fatigue resistance of extruded specimens was evaluated for different passes and applied stresses using fatigue tests, fractography, and metallography. The mechanical properties of the extruded material were obtained at a tensile test velocity of 0.5 mm/min. It was found that the maximum increase in strength occurred after the 2nd pass. The total increase in ultimate strength after eight passes was 94%. The results of fatigue tests indicated that a significant improvement in fatigue life occurred after the 2nd pass. In subsequent passes, the fatigue life con-tinued to improve but at a considerably lower rate. The improved fatigue life was dependent on the number of passes and applied stresses. For low stresses （or high-cycle fatigue）, a maximum increase in fatigue resistance of approximately 500%was observed for the extruded material after eight passes, whereas a maximum fatigue resistance of 5000%was obtained for high-applied stresses （or low-cycle fatigue）. Optical microscopic examinations revealed grain refinements in the range of 32 to 4 μm. A maximum increase in impact energy absorption of 100%was achieved after eight passes. Consistent results were obtained from fractography and metallography examinations of the ex-truded material during fatigue tests.展开更多
The purpose of this investigation was to refine the grains of annealed 6063 aluminum alloy and to improve its yield stress and ul- timate strength. This was accomplished via the equal channel angular extrusion （ECAE...The purpose of this investigation was to refine the grains of annealed 6063 aluminum alloy and to improve its yield stress and ul- timate strength. This was accomplished via the equal channel angular extrusion （ECAE） process at a temperature of 200℃ using route A, with a constant ram speed of 30 mm/min through a die angle of 90° between the die channels for as many as 6 passes. The experiments were conducted on an Avery universal testing machine. The results showed that the grain diameter decreased from 45 μm to 2.8 μm after 6 extru- sion passes. The results also indicated that the major improvement in fatigue resistance occurred after the first pass. The subsequent passes improved the fatigue life but at a considerably lower rate. A maximum increase of 1100% in the case of low applied stresses and an ap- proximately 2200% increase in fatigue resistance in the case of high applied stresses were observed after 5 passes. The improvement of fa- tigue resistance is presumed to be due to （1） a reduction in the size and the number of Si crystals with increasing number of ECAE passes, （2） the aggregation of Cu during the ECAE process, （3） the formation and growth of CuA12 grains, and （4） grain refinement of the A1--6063 alloy during the ECAE process.展开更多
基金the Research Council and the Vice Chancellor of Research Affairs of Islamic Azad Universitythe University Putra Malaysia for its support
文摘In this study, annealed pure copper was extruded using equal channel angular extrusion （ECAE） for a maximum of eight passes. The fatigue resistance of extruded specimens was evaluated for different passes and applied stresses using fatigue tests, fractography, and metallography. The mechanical properties of the extruded material were obtained at a tensile test velocity of 0.5 mm/min. It was found that the maximum increase in strength occurred after the 2nd pass. The total increase in ultimate strength after eight passes was 94%. The results of fatigue tests indicated that a significant improvement in fatigue life occurred after the 2nd pass. In subsequent passes, the fatigue life con-tinued to improve but at a considerably lower rate. The improved fatigue life was dependent on the number of passes and applied stresses. For low stresses （or high-cycle fatigue）, a maximum increase in fatigue resistance of approximately 500%was observed for the extruded material after eight passes, whereas a maximum fatigue resistance of 5000%was obtained for high-applied stresses （or low-cycle fatigue）. Optical microscopic examinations revealed grain refinements in the range of 32 to 4 μm. A maximum increase in impact energy absorption of 100%was achieved after eight passes. Consistent results were obtained from fractography and metallography examinations of the ex-truded material during fatigue tests.
基金the Faculty of Engineering, University Putra Malaysia (UPM) for its supportthe Research Council and the Vice Chancellor of Research Affairs of Islamic Azad University, Takestan Branch, for their financial support
文摘The purpose of this investigation was to refine the grains of annealed 6063 aluminum alloy and to improve its yield stress and ul- timate strength. This was accomplished via the equal channel angular extrusion （ECAE） process at a temperature of 200℃ using route A, with a constant ram speed of 30 mm/min through a die angle of 90° between the die channels for as many as 6 passes. The experiments were conducted on an Avery universal testing machine. The results showed that the grain diameter decreased from 45 μm to 2.8 μm after 6 extru- sion passes. The results also indicated that the major improvement in fatigue resistance occurred after the first pass. The subsequent passes improved the fatigue life but at a considerably lower rate. A maximum increase of 1100% in the case of low applied stresses and an ap- proximately 2200% increase in fatigue resistance in the case of high applied stresses were observed after 5 passes. The improvement of fa- tigue resistance is presumed to be due to （1） a reduction in the size and the number of Si crystals with increasing number of ECAE passes, （2） the aggregation of Cu during the ECAE process, （3） the formation and growth of CuA12 grains, and （4） grain refinement of the A1--6063 alloy during the ECAE process.
