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Showing 3 results for Ultrafine-Grained Materials
Hesam Torabzadeh Kashi, Ghader Faraji,
Volume 15, Issue 8 (10-2015)
Abstract
In this research, a novel severe plastic deformation (SPD) method entitled cyclic flaring and sinking (CFS) is presented for producing of the ultrafine-grained (UFG) thin-walled cylindrical tubes. Finite element (FE) results showed that CFS process has a good strain homogeneity and requiring a low load. CFS process includes two different flaring and sinking half-cycles. At flaring half cycle, the flaring punch with two stepped regions is pressed into the tube. Shear and normal tensile strains are applied as a result of the existence of shear zones and increase in the tube diameter. In the second half cycle, the tube is then pressed to sinking die that applies same shear strains and normal compression strain so that the initial diameter of the tube is achieved and high plastic strain is applied. This process can be run periodically on the tube to exert more strain and consequently finer grain size and ultimately achieve better mechanical properties. The results indicated that the yield and ultimate strengths of the CFS processed Al (1050) tube were significantly increased to 165 MPa, and 173 MPa, respectively from the initial values of 50 MPa, and 115 MPa. The elongation to failure was decreased to about 14% after three cycles from the initial value of 42%. In addition, the hardness increases to ~38 Hv after ten cycles of CFS from ~23 Hv. Keywords
Behzad Binesh, Mehrdad Aghaie-Khafri, Mohammad Daneshi,
Volume 17, Issue 8 (10-2017)
Abstract
In this study, severe plastic deformation of 7075 aluminum alloy was investigated using a new method, based on the combination of conventional upsetting and direct extrusion. In this process, which is called repetitive upsetting-extrusion, cylindrical samples were first subjected to upsetting and were subsequently subjected to extrusion at 250 °C with various processing cycles. Die design was carried out considering the possibility of conducting both upsetting and extrusion by using a single die and the maximum of four RUE cycles were successfully performed on the samples. Finite element method was used to simulate the deformation behavior of 7075 alloy during repetitive upsetting-extrusion processing and the strain distribution was obtained for the deformed samples. The finite element simulation results correlated fairly well with the microstructural observations. Based on the simulation results, the maximum effective strain was observed at the central region of the samples. The deformation behavior and the flow pattern were discussed based on the experimental and the simulation results. In addition, the effect of applied strain on mechanical properties of processed samples was studied. Tensile strength and elongation of deformed samples increased with extending the number of repetitive upsetting-extrusion cycles.
S.a. Hosseini-Moradi , B. Binesh, M.r. Yazdanpanah ,
Volume 19, Issue 11 (11-2019)
Abstract
In this research, semi-constrained groove pressing (SCGP) as one of the severe plastic deformation techniques was investigated to achieve an ultrafine-grained structure in interstitial free steel sheets. The maximum of four semi-constrained groove pressing passes was successfully applied on the samples and the effects of the number of SCGP passes on the microstructure and mechanical properties of the samples were investigated. The microstructural investigations of the deformed specimens indicate that the semi-constrained groove pressing can effectively reduce the grain/crystallite size so that it ranges from about 41 μm in annealed condition to 232 nm after four passes. The results also showed that the strength and hardness of the samples are increased significantly by applying the pressing process. The highest tensile and yield strengths were observed in the two-pass SCGP processed sample, which showed an increase of about 90% and 75%, respectively, compared to the initial sample. The maximum hardness value of 165 Vickers was obtained for a three-pass SCGP processed sample, which is about 68% higher than the annealed sample. Regarding the hardness tests results, the uniformity of deformation increased with increasing the number of SCGP passes. Finite element method was used to simulate the semi-constrained groove pressing, and the strain distribution was obtained for the deformed samples. The finite element simulation results correlated fairly well with the analytical results.
