Consolidation of Titanium-Magnesium Powders by Severe Plastic Deformation for the Production of Dental Implants

نوع: Type: Thesis

مقطع: Segment: PHD

عنوان: Title: Consolidation of Titanium-Magnesium Powders by Severe Plastic Deformation for the Production of Dental Implants

ارائه دهنده: Provider: Elnaz Gharehdaghi

اساتید راهنما: Supervisors: Dr. Faramarz Fereshte-Saniee

اساتید مشاور: Advisory Professors: Dr. Loghman Rezaei-soufi, Dr. Abbas Farmany

اساتید ممتحن یا داور: Examining professors or referees: Dr. Ali Alavi Nia, Dr. Mohammad Bakhshi Jouybari, Dr. Yousef Mazaheri Roudbali

زمان و تاریخ ارائه: Time and date of presentation: 2025

مکان ارائه: Place of presentation: آمفی تئاتر

چکیده: Abstract: In this research, Cyclic Expansion-Extrusion (CEE) was employed as a simple and efficient Severe Plastic Deformation technique. The objective was to consolidate titanium-magnesium powders and produce semi-biodegradable implant rods. The process was applied with two different approaches: the first method involved processing loose powders, while the second method used pre-compacted powders, prepared using Cold Isostatic Pressing. These two methods were compared to evaluate the effect of pre-compaction on the final properties of the produced rods. Titanium powders were mixed with magnesium powders at a volume ratio of 17% and then subjected to the CEE process at a temperature of 400 °C. The study investigated the effects of press speed and the number of CEE passes on the density, mechanical properties (namely compressive strength, hardness, and elastic modulus), microstructure, and corrosion behavior of the produced samples. The results showed that increasing the number of passes increased the density of the samples and reduced the porosity, leading to significant improvements in hardness and mechanical strength. This effect was more pronounced for the loose powders. The final compressive strength values of the composites produced in this study ranged from 354 to 712 MPa. Some samples exhibited up to a 30% increase in strength compared to Grade 4 titanium. These values, in terms of compressive strength, are comparable to the range of natural human bone strength, indicating the high potential of these composites for biomedical applications, particularly in the fabrication of bone implants. The addition of magnesium led to a 20–40% reduction in the elastic modulus (depending on the processing conditions), which is highly desirable for minimizing the “stress shielding effect” in bone tissue. Microstructural analyses, using XRD and SEM, revealed that magnesium was uniformly distributed in the titanium matrix, with no intermetallic phases formed. Hence, the Ti-Mg composite product has been a suitable candidate for biomechanical applications. The corrosion test results indicate the superior corrosion resistance of samples prepared via the CEE method compared to those produced by other methods. Furthermore, an increase in the number of passes during the CEE process leads to a significant enhancement in the corrosion resistance of the implantable samples. Statistical analyses also underscore the more pronounced influence of the number of passes in the CEE process relative to pressing speed on the mechanical and physical properties of the samples. By optimizing the CEE process parameters, the mechanical properties of Ti-Mg implants can be tailored to meet specific medical requirements. This study has highlighted the great potential of the CEE method for producing durable and biocompatible implants with favorable mechanical, structural and corrosion properties.

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