Simulation and Experimental Investigation for the Homogeneity of Ti49.2Ni50.8 Alloy Processed by Equal Channel Angular Pressing

Diantao Zhang,Mohamed Osman,Yufeng Zheng,Li Li,Yunxiang Tong

doi:10.3390/met6030045

Diantao Zhang, Mohamed Osman + Show 3 more

Open Access

https://doi.org/10.3390/met6030045

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Journal: Metals	Publication Date: Feb 25, 2016
Citations: 26	License type: CC BY 4.0

Affiliation: Harbin Engineering University, Peking University

Abstract

Ti49.2Ni50.8 shape memory alloy (SMA) was processed by equal channel angular pressing (ECAP) for eight passes at 450 °C. The deformation homogeneity was analyzed on various planes across the thickness by Deform-3D software. Strain standard deviation (SSD) was used to quantify deformation homogeneity. The simulation result shows that the strain homogeneity is optimized by the third pass. Deformation homogeneity of ECAP was analyzed experimentally using microhardness measurements. Experimental results show that the gradual evolution of hardness with increasing numbers of passes existed and the optimum homogeneity was achieved after three passes. This is in good agreement with simulation results.

Highlights

TiNi-based shape memory alloys (SMAs) are considered one of the most promising materials for engineering and biomedical applications due to their unique shape memory effect and superelasticity [1,2]
The degree of strain distribution homogeneity was calculated from the simulation model by a mathematical coefficient called strain standard deviation (SSD) [20]: d2 řni“1 εiεavg
The ECAPed billet was cut to the same three planes as in the simulation model (Figure 2) using the low speed diamond saw cutting machine to avoid the possible change of microstructure

Summary

Introduction

TiNi-based shape memory alloys (SMAs) are considered one of the most promising materials for engineering and biomedical applications due to their unique shape memory effect and superelasticity [1,2]. In order to further improve the functional properties of TiNi SMAs, severe plastic deformation (SPD) methods have been employed to refine the microstructure of alloys [3]. In 2002, Pushin and his coworkers carried out the first ECAP of TiNi alloys and the grain size was reduced from 50–80 μm to. During conventional ECAP processing, an inhomogeneous microstructure may be achieved due to die geometry [7], friction [8] and strain hardenability of material [9]. FEM was used to analyze the deformation the deformation behavior and estimate the developed strain in the ECAP process [16,17,18]. In order to obtain the data of flow stress, Systems Inc, Poestenkill, NY, USA) at different strain rates. The conditions, including geometry process of parameters, the length of 60 mm.number, The simulation conditions, including and process parameters, the FEM elements meshing method as well asgeometry the physical properties of Ti49.2

Figure

Homogeneity Calculation

Experimental Details

Results and Discussion

The blank region in Figure

Conclusions