Abstract
Processing by Equal-Channel Angular Pressing (ECAP) is generally considered superior to most other SPD techniques because it uses relatively large bulk samples. However, due to their low deformability it has proven almost impossible to successfully process NiTi alloys by ECAP at room temperature and therefore the processing is conducted at elevated temperatures. Recently, a new billet design was introduced and it was used to achieve the successful processing of NiTi shape memory alloys by ECAP. In this procedure, a NiTi alloy was inserted as a core within an Fe sheath to give a core-sheath billet. In this research, a NiTi was processed by one pass ECAP with this new billet design at room temperature. The structural evolution during annealing was investigated by X-ray diffraction (XRD) and microhardness measurements. Post deformation annealing (PDA) was carried out at 400°C for 5 to 300 min and the results indicate that the shape memory effect improves by PDA after ECAP.
Highlights
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NiTi alloys are known as the most important shape memory alloys because of their many applications based on the shape memory effect and superelasticity [1]
It seems martensite reorientation does not take place after the heavy deformation and the stress level decreases by increasing the annealing time from 0 to 30 min as a result of decreasing the density of dislocations which act as an obstacle for detwinning. These results indicate that the shape memory effect is improved significantly after Post deformation annealing (PDA) in comparison with solution annealing (SA) and Equal-Channel Angular Pressing (ECAP) condition
Summary
This content has been downloaded from IOPscience. Please scroll down to see the full text. 63 012111 (http://iopscience.iop.org/1757-899X/63/1/012111) View the table of contents for this issue, or go to the journal homepage for more. Download details: IP Address: 152.78.130.228 This content was downloaded on 12/09/2014 at 13:30 Please note that terms and conditions apply
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