Materials selection properties Materials selection properties Materials selection

Materials selection - properties

Materials selection - properties

Materials selection - properties

Materials selection - environment

Bicycle frames

Bicycle frames

Bicycle frames – hot piercing for seamless tubing

Bicycle frames – cold drawing of seamless tubing Cold drawing – need high formability ––> extensive work-hardening

Bicycle frames

Bicycle frames

Bicycle frames – common materials used Plain carbon steel Cr-Mo steel 6061–T 6 Ti-3 Al-2. 5 V Polymer composite Plain carbon steel Cr-Mo steel 6061–T 6 Ti-3 Al-2. 5 V density 7. 8 gm/cc 7. 8 2. 7 4. 5 modulus 200 GPa 200 70 110 yield 240 MPa 485 260 700 yield/density 30 62 95 156

A little bit more on Ti and its alloys Ti is polymorphic: -Ti (hcp) ––> -Ti(A 2) at 882°C Ti mostly alloyed with Al, V Remember - & -Fe w/ chromium, & nickel Various elements have different solubilities in - & -Ti

A little bit more on Ti and its alloys Ti-3 Al-2. 5 V is an " - alloy" Enuf -stabilizer (V) added so that a little phase can exist at room temp & phase solution strengthened by Al & V alloys are stronger than those containing only or phase

Joining techniques Conventional arc welding Tungsten inert gas (TIG) welding Brazing Adhesive bonding

Joining techniques Plain carbon steel frame – TIG welded Tubing is strengthened by drawing operation – but softened near weld Use butted tubing for strengthening HAZ region

Joining techniques Cr-Mo steel frame – TIG welded But weld and HAZ harder than tubing – more rapid cooling than that experienced by tubing – get Bainite original tube