Creep of tantalum under cyclic elevated temperatures
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Ames National Laboratory is a government-owned, contractor-operated national laboratory of the U.S. Department of Energy (DOE), operated by and located on the campus of Iowa State University in Ames, Iowa.
For more than 70 years, the Ames National Laboratory has successfully partnered with Iowa State University, and is unique among the 17 DOE laboratories in that it is physically located on the campus of a major research university. Many of the scientists and administrators at the Laboratory also hold faculty positions at the University and the Laboratory has access to both undergraduate and graduate student talent.
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Abstract
An initial study was conducted on the effects of cyclic temperature variations of small amplitudes upon the creep properties of tantalum. The results show a marked weakening of the material when a temperature variation of a few degrees is applied in a sinusoidal manner at a rate of one cycle per hour.
Application of a temperature compensated time parameter for the prediction of the cyclic temperature curves is inadequate to explain the observed increase in creep rate. With vacuum arc-cast tantalum, possessing high initial cold work, relief of the residual cold work strain appears to contribute to the acceleration of the strain rate as evidenced by a reduction in hardness after the cyclic temperature application. Sintered tantalum showed a similar acceleration of the creep rate under cyclic temperatures without a change in hardness . Experimental results indicate that an optimum temperature condition may exist for plastic deformation to occur under cyclic temperatures.