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

density modulusPlain carbon steel 7.8 gm/cc 200GPaCr-Mo steel 7.8 2006061–T6 2.7 70Ti-3Al-2.5V 4.5 110Polymer composite

yield yield/densityPlain carbon steel 240 MPa 30Cr-Mo steel 485 626061–T6 260 95Ti-3Al-2.5V 700 156

A little bit more on Ti and its alloys

Ti is polymorphic: -Ti (hcp) ––> -Ti(A2) at 882°CTi 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-3Al-2.5V 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