Is there any material which has the same properties of aluminium in its specific heat, thermal conductivity, density but has higher melting point of nearly 1000°C when compared to aluminium's?
It ineeds to be used for exhaust valve application in IC engines.
Have a look at the annual report on our site to see some of the research we have been doing. This may be useful in answering your question.
http://www.lime.ac.uk
I suggest you look at Ashby's textbooks about this. He gives a rigorous method to address issues like this with his maps of material properties.
And I also suggest you think about the limits you set on a given property.
Does it really have to have the SAME density etc etc.
Or close to it.
Or does the density actually matter and perhaps you are looking a something else.
Anyway, Ashby is your man.
He's written about 3 or 4 textbooks on this exact subject.
Your library should have copies.
You are looking for the holy grail of materiasl and it doesn't currently exist. That is why they use nickel and cobalt base superalloys at 1000°C, and even those often need coatings to prevent oxidation. As Thomas Grund suggested, Titanium Aluminides would be closest thing but they are expensive and difficult to work with. Or you could look at ceramics such as Silicon Nitride.
@all: thanks for all your suggestions. Most of you told that titanium can be an alternative. I have mentioned that it should have few of the properties similar to aluminium. The cost of titanium has to be taken into consideration. In addition to it, the density of titanium is little high which can be tolerable. But I mentioned it as engine application, so heat plays a important role which means that the heat transfer rate is one of the important consideration. The thermal conductivity of titanium is ver very less, its a kind of insulator so the it didn't satisfies the main criteria.
Next is magnesium: Magnesium satisfies only the density criteria. Thermal conductivity is little reasonable and ofcourse cost too. But the melting point is very less for it so that the metal will melt inside the engine combustion chamber. In addition, inside the engine all types of stress will be acting and the Young's Modulus of the element is less such that it can't withstand the stress acting on it.
@Matt Pohlman- I think the suggestion you gave will be better for the application. Till now from the datas I have collected I found that its melting point and density criteria satisfies my application. But I was not able to find its thermal conductivity and cost. Can anyone tell me a better link for finding the mechanical, Thermal, and Chemical properties of silicon nitride? I also want its cost criteria!
This one for you....
Http://www-materials.eng.cam.ac.uk/mpsite/interactive_charts/
Hi Ram, if your application is engine exhaust valves, you can forget about Al, Mg, Ti and also most of TiAl alloys, as they simply will not work (for many reasons). Besides properties you have listed, there is impact wear, sulfur hot corrosion, oxidation, HCF, carbonization, SCC, TMF, etc., etc., which do not allow even coated TiAl to perform well.
Of course one may invent fancy composite valves, but the cost is prohibitive.
The only alloy which was more or less suitable, is the high-Si Ti-Zr-Al-based composite alloy (also may have some boron), but it needs tricky processing. Some similar alloys with Nb-Si additions also may work, but due to higher density, only hot part of the valve could be formed withe those.
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