Larry, You are right that 6061 T6 is far and away the most common alloy.
But heating will alter the temper (the T6 suffix) and weaken the part. For
example, 6061 tensile strength is 18,000 psi annealed, 45,000 psi for T6.
Something to keep in mind. Your advice to remove the damaged surface
layer is good, as stress concentration can be 2-3x higher at the root of
notches and cracks. But a fatigue crack can initiate even in apparently
flawless metal, which is why mechanics are alway inspecting airplane skins
around rivets (those dang stress concentrations again). Your practical
experience is an example of what you can do. But in general aluminum
is much less forgiving than steel.
/Bill
> from:larrybsp@aol.com (Larry Stark)
>
> Jim,
> Several factors come into play when bending aluminum, alloy being the most
> important. Most of the commercial alloys are 6061 T6, the T6 indicating it
> has been solution heat treated and aged. It has also been roll formed.
> This stuff is not easy to bend. I've had success by heating the outside of
> the bend with an acetylene torch while bending the material. Plenty of heat
> is needed because the aluminum carries the heat away quickly. You may still
> get some surface cracking. To prevent further problems grind/sand down the
> cracks to clean solid metal. This eliminates the places for a fatigue crack
> to initiate. It worked for me.
>
> Larry
>
> In a message dated 8/10/01 8:47:40 AM Pacific Daylight Time, billh@pa.dec.com
> writes:
>
> << Subj: Re: trouble bending aluminum sway bar arms, advice?
> Date: 8/10/01 8:47:40 AM Pacific Daylight Time
> From: billh@pa.dec.com (Bill Hamburgen 650-617-3329 FAX -3374)
> Sender: owner-ba-autox@autox.team.net
> To: black94pgt@pacbell.net
> CC: billh@pa.dec.com, ba-autox@autox.team.net
>
> > im trying to bend the speedway engineering sway bar arms i have. they are
> > about 1/2 thick and 1 inch across. i heated them to c. 550 F and quenched
> > to anneal them, but even then i could not bend it even 1 degree.
>
> James,
>
> Don't!!!! Aluminum has completely different properties than steel and if
> you don't know the alloy and how it's been treated, you're begging for
> crack initiation and eventual fatigue failure.
>
> Your heat/quench may have already damaged the bar. You might call Speedway
> and get their opinion - probably something like "Why'd ya do dat??". I sort
> of doubt they'll tell you much. If you care about sway bar failure, you
> might want to have it inspected for cracks after it's been in service a
> little while. I think fluorescent dye penetrant is how it's done.
>
>
> /Bill
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