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Karaj, Iran

Nafari Q. M.,AMR of Technology | Abbasi S.M.,Advanced Materials Research Laboratory
Transactions of the Indian Institute of Metals | Year: 2013

The effects of composition, specially the Cu element and thermomechanical training process on the transformation and one way shape memory behavior (OWSM) of NiTi based alloys were investigated using differential scanning calorimetry and microstructural analysis. The hot rolled strips with different compositions were trained under various applied pre-strains by bending test at martensitic state. It was found that the presence of Cu in the NiTi alloy results in an improvement of the OWSM effect by reducing the transformation hysteresis and forming the longer martensitic variants with lower interfacial energy than the NiTi binary alloys. Increasing the applied pre-strain and the number of thermomechanical training cycles caused OWSM effect to decrease. Although the transformation temperature increased at the higher applied pre-strain, it was reduced during the thermomechanical training process. © 2013 Indian Institute of Metals. Source

Shore F.M.,AMR of Technology | Morakabati M.,AMR of Technology | Mahdavi R.,AMR of Technology
International Journal of Materials Research | Year: 2014

Hot ductility was investigated in Incoloy901 using hot tensile testing over a temperature range of 900 to 1 200 °C and at strain rates of 0.01 to 1 s-1, in the cast and wrought conditions. Maximum ductility was detected in the cast and wrought conditions at temperature ranges of 1 000 to 1 050 °C and 1 000 to 1 100 °C, respectively. More voids were seen at the fracture surface of the wrought specimens compared to the cast ones. At 950 °C, the formation of large and non-homogeneous voids at the fracture surface, as well as the appearance of transgranular and intergranular cracks in the wrought specimen, support moderate ductility of the alloy. Microstructural analysis does not support the occurrence of dynamic recrystallization in the cast specimens. In contrast, dynamic recrystallization in the wrought specimens at the region of maximum hot ductility promoted diffusion, leading to ductile fracture. At temperatures higher than the maximum ductility range, the formation of intergranular cracks resulted in a remarkable decline in ductility. © Carl Hanser Verlag GmbH & Co. KG. Source

Sheikhali A.H.,AMR of Technology | Morakkabati M.,AMR of Technology | Abbasi S.M.,AMR of Technology | Rezaei A.,AMR of Technology
International Journal of Materials Research | Year: 2013

The superplastic behavior of Ti-13V-11Cr-3Al alloy with beta single phase structure and average grain size of 220 l m was investigated. It was found that elongation increases with temperature at strain rates of 0.1 and 1 s -1. The optimum condition for superplastic deformation of the alloy was achieved in the temperature range 1 030- 1 080 ° C and with a strain rate of 0.1 s-1. In this condition the amount of elongation reaches 200 %. Grain refinement occurred during deformation which can be attributed to the occurrence of dynamic recovery and continuous dynamic recrystallization. In addition, it was seen that in the temperature range 930-1 080 ° C, the strain rate sensitivity parameter (m) was higher than 0.3, which is an appropriate value for superplastic deformation. A high value of m, elongation over 100 %, and coarse-grained microstructure of the alloy suggested that superplastic behavior of the Ti-13V-11Cr-3Al alloy can be similar to the behavior of coarsegrained superplastic alloys. © Carl Hanser Verlag GmbH & Co. KG. Source

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