BME213 Sem 4 Flashcards
What is an alloy? Why is it different from pure metal?
An alloy is a mixture of two or more elements, where at least one is a metal.
It’s designed to have improved properties compared to pure metals.
What are the 3 most widely used metal alloy classes in medical applications?
- Stainless Steel (e.g., SS316L)
- Cobalt-Chromium (e.g., ASTM F75)
- Titanium Alloys (e.g., Ti-6Al-4V)
For SS306L, what does L note mean?
L note means Low carbon ( >0.03%)
For SS306L, why does Carbon % need to be less than 0.03%?
To reduce the possibility of in Vivo corrosion (Stress Corrosion Cracking)
When C>0.03%, carbides form at the grain boundaries
Steel prone to fail through corrosion-assisted fractures that originated at the grain boundaries
Justify the usage of titanium as stem in artificial hip joint implant
- Titanium has impressive corrosion resistance property due to the presence of thin protective layer of TiO2 on the surface of the Ti metal
- Titanium is also bio active an promoting Osseo-integration forming strong bonding between the material and the host bone tissue, owing to the presence of the TiO2 which is highly bioactive
- Titanium has an excellent strength to weight ratio (lower dentistry) compared to stainless steel, hence giving comfort to the patient. The implant will be light but yet strong enough to have adequate mechanical property
- Titanium’s modulus is only half that of stainless steel, so the remaining in bones will suffer less from stress shielding
- In addition, by controlling the porosity of titanium, we can match the stiffness of Ti to the stiffness of the cortical bone
What is annealing in heat treatment?
Annealing is a heat treatment process where metal is heated to a specific temperature, held, and then cooled slowly, usually in a furnace.
Give 1 example and use of a Stainless Steel alloy in medicine.
Example: SS316L
Use: Bone plates, screws, surgical tools
Give 1 example and use of a Cobalt-Chromium alloy in medicine.
Example: ASTM F75 Co-Cr alloy
Use: Joint replacements, dental implants
Give 1 example and use of a Titanium alloy in medicine.
Example: Ti-6Al-4V
Use: Hip implants, dental implants, pacemaker housings
Which alloy class offers the best biocompatibility?
Titanium alloys — they promote osseointegration and are lightweight and corrosion-resistant.
Compare Stainless Steel, Co-Cr, and Titanium alloys by strength and corrosion resistance.
Stainless Steel: Moderate strength, good corrosion resistance
Co-Cr: Very high strength, excellent wear & corrosion resistance
Titanium: High strength, excellent corrosion resistance, most biocompatible
What is quenching in heat treatment?
Quenching is a heat treatment process where metal is heated to a high temperature and then rapidly cooled, typically in water or oil.
What are the effects of annealing on metal properties?
• Increases ductility
• Reduces hardness
• Relieves internal stresses
• Improves machinability
• Refines grain structure
What are the effects of quenching on metal properties?
• Increases hardness and strength
• Reduces ductility
• May cause internal stresses or brittleness
• Creates a harder, more wear-resistant structur
Key difference between annealing and quenching?
Annealing = slow cooling to soften metal
Quenching = rapid cooling to harden metal
