Tezin Türü: Yüksek Lisans
Tezin Yürütüldüğü Kurum: Yıldız Teknik Üniversitesi, Fen Bilimleri Enstitüsü, Metaluji ve Maleme Mühendisliği, Türkiye
Tezin Onay Tarihi: 2018
Tezin Dili: İngilizce
Öğrenci: MAZIN SALAH ABED ABED
Danışman: Hakan Yılmazer
Özet:
Stainless steel was the first modern metal to be used as a structural biomaterial. In 1931,
stainless steel was applied in the first femoral neck fixation device. After a few years, in
1936, the alloy cobalt-chromium was used for bone plates. Then, a decade later in 1947,
Titanium and its alloy were used for bone plates and hip joints.
The difference in the value of young modulus between bone and metal causes stress
shielding when implanted in bone. This impact wears far the bone and causes the implant to loosen and finally lose the mission's ability. The young modulus of bone is around
30 GPa, while the modulus of stainless steel, cobalt-chromium and titanium are 200,
230 and 127 GPa respectively. However, the young modulus of beta phase titanium can
be reduced to as 40 GPa, with suitable alloying elements additions. The last few
decades have seen an increase in the use of β titanium alloy as structural biomaterials.
Their combination of excellent mechanical properties, corrosion resistance and
biocompatibility, along with a lower Young’s modulus than stainless steel, cobaltchromium and commercially pure titanium make the β titanium alloys ideal
biomaterials β type titanium alloy Ti-29Nb-13Ta-4.6Zr, (referred as TNTZ), with low elastic
modulus has been developed for biomedical applications, and utilization is being taken
into account.
In this study, thermomechanical heat treatments and their effects on the microstructure
and mechanical properties of severely deformed TNTZ have been systematically
investigated. TNTZST5,10,30 and 60 following by water quenching and air cooling has been
applied on the severely cold rolled TNTZ with an over 90% reduction ratio, designed as TNTZCR. While, microstructural features have been analyzed using optical
microscopy, XRD and SEM, mechanical tests such as using hardness measurements,
tensile and fatigue tests have been carried out to analyze mechanical behavior. The
optical microstructure of TNTZST was observed only single β phase with an equiaxed
coarse grain structure and an average grain size of about 57 μm. On the other side the
microstructure of TNTZCR do not observed because of high dislocation density with
rolling direction. In addition TNTZST-WQ and TNTZST-AC are observed grain boundaries
with an average grain size around (6-11 μm) after annealing above 10 minutes.
The (XRD) of TNTZST and TNTZCR are composed only single β phase. The (XRD)
profiles of TNTZST5-WQ and TNTZST5-WQ samples shown α″ martensitic phase are
formed in β matrix. It is considered that the β (110) was the strongest peak in both air
cooling and water quenching treatments.The Vickers hardness measurements of
TNTZCR samples. The average hardness values are 189 and 251 HV for TNTZST and
TNTZCR, respectively. The optimum value of hardness measurement was evaluated
under TNTZST-60-AC. Its hardness value is 261 HV. The stress-strain curve of TNTZST-10-
WQ show highest yield strength about 448 MPa and ultimate tensile strength ~1200 MPa.
Whereas, the TNTZST-5-WQ curve shows minimum yield strength 259 MPa and tensile strength 950 MPa. The maximum yield strength was shown by TNTZST-5-AC. The yield
strength and ultimate tensile strength of TNTZST-5-AC is 600 MPa and 1300 MPa
respectively. While minimum yield strength and ultimate tensile strength shown by
TNTZST-60-AC. It’s observed yield strength 252 MPa and ultimate tensile strength more
than 1200 MPa. The SEM fractography analysis of the tensile specimens showed that
all TNTZ annealed of titanium alloys experience ductile failure. Ductile behavior is
desirable in biomedical applications. In additional, TNTZST-30-WQ and TNTZST-60-WQ
surfaces showed significantly compatible for cell adhesion. TNTZST-30-WQ and TNTZST60-WQ surfaces showed significantly compatible for cell adhesion. NIH-3T3 cells exhibits well- developed and increased the filaments to contact with each other on the TNTZSTAC-30 and TNTZST-30-WQ and TNTZST-60-AC and TNTZST-60-WQ.