The Use of Strain Softening to Improve the Properties of Refractory Metals

摘要

Work has been continuing to determine the flexing procedure that will result in the maximum lowering of transition temperature. Unfortunately, the scatter in NDT for the most recently obtained heat of Mo-0.5 Ti alloy is so broad (approximately 80F) it has been difficult to evaluate property changes. Attempts will be made to reduce the scatter range by improving the surface finish using mechanical and electrochemical finishes. In spite of the excessive scatter, a general behavior pattern appears to be developing: Flexing does not cause a uniform lowering of the transition temperature as one might expect, for example, with a continuous decrease in interstitial content. Instead, the bend-angle vs. testing temperature curve is similar to the as-received one down to the vicinity of the NDT temperature (possibly with a lower shelf height). At still lower temperatures a ductility recovery occurs causing a hump or double transition. The cause for this is still not known, but it appears that the length of the slip element is decreased by flexing. (Author)