FEATURES OF THE B2 PHASE STRUCTURE CHANGE IN THE NiTi SURFACE LAYER AFTER PULSED ELECTRON-BEAM IMPACT

L L Meisner,M G Ostapenko,V O Semin,A I Lotkov,A A Neiman

doi:10.17073/0368-0797-2014-8-60-65

Abstract

By X-ray diffraction, optical, scanning and transmission electron microscopy methods the structural-phase state of NiTi surface layers affected by low-energy high-current electron beams have been investigated. It was found that during treatment in recrystallized layer thickness of 8 – 10 μm a nonequilibrium single-phase structural state forms, which is characterized by a deformed B2 based phase structure, textured in a direction close to the . The downstream with depths ranging from 10 to 20 μm layer except B2 phase with insigniﬁcant distortions of the crystal lattice contains a small volume fracture (up to 5 vol. %) of martensitic phase with В19′ structure. As a result of electron-beam treatment the modiﬁed layer chemical composition has changed to titanium enrichment due to Ti2Ni phase particles melting. At the same time intervals of martensitic transformations are shifted to higher temperatures thus even at room temperature can be expected that in the present layer the main structural state is martensitic. Using transmission electron microscopy the studies have showed that in the modiﬁed layer the martensitic phase is not observed. The assumption, explaining the created by a pulsed electron beam impact on the NiTi surface structure-phase state is expressed.

Highlights

By X-ray diffraction, optical, scanning and transmission electron microscopy methods the structural-phase state of NiTi surface layers affected by low-energy high-current electron beams have been investigated
It was found that during treatment in recrystallized layer thickness of 8 – 10 μm a nonequilibrium single-phase structural state forms, which is characterized by a deformed B2 based phase structure, textured in a direction close to the
At the same time intervals of martensitic transformations are shifted to higher temperatures even at room temperature can be expected that in the present layer the main structural state is martensitic

Summary

Introduction

ОСОБЕННОСТИ ИЗМЕНЕНИЯ СТРУКТУРЫ ФАЗЫ В2 В ПОВЕРХНОСТНОМ СЛОЕ НИКЕЛИДА ТИТАНА ПОСЛЕ ИМПУЛЬСНОГО После облучения образца электронным пучком, согласно данным РСА, объемная доля фазы В2 составляет 95 % или менее 95 % После электронно-пучкового воздействия частицы Ti2Ni обнаруживаются лишь на глубине 8 – 10 мкм от поверхности и практически отсутствуют в приповерхностном модифицированном слое

Results

Conclusion