Abstract
Due to the combination of lightness, high specific strength and corrosion resistance, titanium and its alloys are highly interesting for applying in many areas of industry (mechanical engineering, shipbuilding, and aircraft manufacturing). Technically pure titanium is the first choice to be used in medicine because of its high biocompatibility and lack of toxic elements. Pure titanium has high ductility and corrosion resistance but it is inferior to titanium alloys in other mechanical characteristics, such as tensile strength, yield strength, and hardness. Megaplastic deformation (MPD) is a promising method for increasing the strength of titanium to the level of highly alloyed alloys. The paper deals with the study of the influence of MPD in the Bridgman chamber on the structure (phase transformations occurring in technically pure VT1-00 and VT1-0 titanium), corrosion resistance, and microhardness. Using the high-pressure torsion (HPT), the authors obtained samples with different degrees of deformation: from 0.25 to 4 revolutions of the movable anvil. The authors carried out the X-ray diffraction analysis and electrochemical tests of samples and studied the phase composition of titanium samples of two grades containing 0.1 and 0.3 % of impurities before and after MPD. The study identified that the HPT led to the formation of a two-phase mixture a+ɷ. The results showed the positive effect of MPD on the mechanical properties of titanium. The microhardness of the deformed material increases in comparison with the initial state, while there is no deterioration in the corrosion resistance in the studied environment. Under all deformation modes, titanium stays in a passive state. For the VT1-0 alloy, the stationary corrosion potentials of samples after HPT have a more positive value compared to the original undeformed material.
Highlights
Уже при малых степенях деформации (N=1⁄4) микротвердость марки ВТ1-0 возрастает с 2,6 до 3,75 ГПа, для титана ВТ1-00 – с 2,35 до 2,95 ГПа, затем изменяется незначительно
Balakrishnan A., Lee B.C., Kima T.N., Panigrahib B.B. Corrosion behavior of ultra fine grained titanium in simulated body fluid for implant application // Trends in Biomaterials and Artificial Organs
Summary
В качестве материала для исследований были выбраны технически чистый (ВТ1-0) и максимально технически чистый (ВТ1-00) титан для изучения влияния небольшого количества примесей на изменение структуры и коррозионной стойкости в процессе МПД. Химический состав образцов соответствует ГОСТ 19807-91, он приведен в таблице 1. Эксперимент проводился при комнатной температуре со скоростью вращения подвижного бойка 1 об/мин. Рентгеноструктурный анализ проводился на дифрактометре ДРОН-3 с использованием излучения СuКα (λ=1,54178 A). Оценка коррозионной стойкости образцов проводилась с использованием потенциостата IPC-Pro 3А. Исследование коррозионного поведения титана проводилось в 1 M HCl. За величину стационарного потенциала коррозии (Еcor) принимали значение потенциала образца после выдержки в коррозионной среде без поляризации в течение 1 ч. Химический состав материала, % (ГОСТ 19807-91) Table 1. Трех месяцев выдерживались при комнатной температуре в исследуемой среде, при этом через определенные промежутки времени производилась фиксация бестокового стационарного потенциала Еcor. При определении микротвердости (HV) использовали метод Виккерса (ГОСТ Р ИСО 6507-1-2007).
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