Mechanism of surface modifications on a NiTi alloy treated with low energy high current pulsed electron beam

¹ Laboratoire d'Étude des Textures et Applications aux Matériaux (LETAM), UMR-CNRS 7078, Université Paul Verlaine, Metz, Ile du Saulcy, 57045 Metz, France
² State Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, Dalian University of Technology, Dalian 116024, P.R. China
³ Laboratoire de Physique des Matériaux (LPM), UMR-CNRS 7556, École des Mines, Parc de Saurupt, 54042 Nancy, France

Corresponding author: jianxin.zou@univ-metz.fr

Received: 28 November 2007
Revised: 27 February 2008
Accepted: 3 March 2008
Published online: 30 April 2008

Abstract

A NiTi shape memory alloy was subjected to low energy high current pulsed electron beam (LEHCPEB) irradiation. The samples were treated with the same electron beam parameters and increasing number of pulses. The treatment induces superfast melting, evaporation and rapid solidification at the top surface. As a result of selective evaporation of Ni, the Ti content was increased in the melted layer of the 5 pulse treated sample. However, for the 10 pulsed sample, a part of the vapor condensed on the surface. It is shown also that in the sub-surface, below the melted layer, the martensitic transformation was triggered due to the effects of the thermal stresses and shock waves propagating in the material.