Aluminum(Aluminium) knife blades?

C

CliveJericho

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Sep 29, 2009
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51
I know that in some cases, aluminum is used for knife handles and other hardware.

what I'm wondering is, how feasible would a cast aluminum knife be(more specifically, a dive knife)?

Unfortunately, cast aluminum isn't very hard(less than 25 on the Rockwell C scale).

The good news is that, once I anodize it, an aluminum piece can easily hit 70RC(and I've heard that it it go as high as 80!). the anodized aluminum can also be dyed and is quite corrosion resistant.

The other factor I like is how light it is. Aluminum is almost 1/3 the weight of the same volume of steel.

I think that this could be an amazing material to work with. A hardness of 70-80RC would hold a wicked edge.

what's your opinions on this? Would the lower hardness on the inside of the piece compromise the blade, or would it act more like a differential heat treatment?
 
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Found this on-line:
Question:"Can someone familiar with anodizing process tell what type of Rockwell hardness can be achieved? How much can one increase the hardness of an aluminum workpiece surface?"
Response:"You can not get a true Rockwell hardness on anodize, You need a microhardness which you can only partially equate to a Rockwell. Reason, the anodize layer is a ceramic and the aluminum will give way enough, causing the ceramic coating to fracture and give you a low reading."
Source: http://www.finishing.com/330/49.shtml

Another source mentioned that the anodized surface can equate to several .001"'s. It would seem that once you sharpen it, the much softer aluminum would be exposed.

I am not a metallurgist but several on here are (Kevin C. for example), and can add a more technical response.
 
I was afraid of that. I just did some research and it looks like the maximum thickness of the anodized layer is about 0.15mm. so that means at the edge I can get about 0.3mm thick, no quite enough to do a god job.
 
The weight of a dive knife is not too critical underwater. You can make it part of your weight belt. Many organized dives do not allow knives. Cast Aluminum is quite porous. Forged Aluminum is much stronger. The thickness of a clear anodize coat is 0.0003". This is the specification for exterior automotive trim. The coating is pure Aluminum oxide which is an abrasive (corundum), but a thin brittle coat on a relatively soft substrate will not survive use as a cutting tool. Beta hardened Titanium would make an excellent dive knife. There are some nitrogen chemistry steels that also make good dive knives.
 
the main reason for my asking is that I had put together a aluminum casting forge last weekend. I guess I could simply make cast aluminum handles.
 
I've got a good sized piece of Ti if you want some of it for the cost of shipping.

ti.jpg
 
thanks for the offer but i don't have the tools to work titanium. perhaps i'll take you up on the offer in a few months time.
 
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