Effect of Elevated Temperature on UTS of Aluminium
Effect of Elevated Temperature on UTS of Aluminium
(OP)
I have a question regarding the degradation in mechanical properties of 6061-T6 aluminium alloy at elevated temperatures.
The application involves operation at 250degC which creates quite a severe reduction in the strength properties. If I review published data (ESDU, MMPDS-4 etc) there are heat factor curves typically for 1hr, 10hr, 1000hr and 10,000hr soak times. For my application it will only be subjected to the elevated temperature for a maximum of 10-hours in any usage cycle. However, over the life of the vehicle the total exposure time will run into thousands of hours.
My interpretation is that the 10-hour curve should be used as this is the maximum soak time. However, I have had conflicting advice that the effect is cumulative and therefore the 10,000-hour curve should be used. At the operating temperatures at which this equipment is exposed this will make a big difference in the allowable strength properties.
Any advice gratefully received!
Peter
The application involves operation at 250degC which creates quite a severe reduction in the strength properties. If I review published data (ESDU, MMPDS-4 etc) there are heat factor curves typically for 1hr, 10hr, 1000hr and 10,000hr soak times. For my application it will only be subjected to the elevated temperature for a maximum of 10-hours in any usage cycle. However, over the life of the vehicle the total exposure time will run into thousands of hours.
My interpretation is that the 10-hour curve should be used as this is the maximum soak time. However, I have had conflicting advice that the effect is cumulative and therefore the 10,000-hour curve should be used. At the operating temperatures at which this equipment is exposed this will make a big difference in the allowable strength properties.
Any advice gratefully received!
Peter





RE: Effect of Elevated Temperature on UTS of Aluminium
Use the 10,000 hr curve.
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P.E. Metallurgy, Plymouth Tube
RE: Effect of Elevated Temperature on UTS of Aluminium
RE: Effect of Elevated Temperature on UTS of Aluminium
RE: Effect of Elevated Temperature on UTS of Aluminium
Aluminum is a VERY poor choice for material in the temperature range You've noted... especially 6061.
6061-T6 is service rated ~300F... but anything more than VERY short spikes [a few minutes] at 250C/485F will degrade it to an oxidized and annealed condition very swiftly.
The only structural material I am aware of that can sustain operational temps at 350F [barely] is 2219-T6... and that should be anodized or [better] IVD [pure] aluminum coated to minimize oxidation.
Unsure what aluminum alloys are used for high performance pistons... but they would be 'best suited' for sustained high temp/stress operations.... but 485F is a sketchy 'stretch' for any aluminum alloy.
HOWEVER IF You really see a steady 485F, and minimum mass combined with strength/stiffness retention is required, then You need to consider titanium or steel alloys... with anodic, metallic or ceramic coatings for an oxidizing atmosphere.
Regards, Wil Taylor
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RE: Effect of Elevated Temperature on UTS of Aluminium