| 摘要 |
Some metallic compositions which, on heating or cooling to a critical temperature range, undergo a reversible transformation between the austenitic and martensitic states, can entirely or partially lose the ability to return from the martensitic state into the austenitic state. This loss of reversibility can be prevented or inhibited if the composition is subjected before its transformation into the martensitic state to an "ageing process" by holding it for a time at a temperature at which it is in the austenitic state. The time needed for a noticeable inhibition of the reversibility loss can vary with the composition. At a specific composition, the time needed shortens at the rate at which the temperature is increased. The ability of a composition to respond to a pretreatment, by means of which its AS temperature can be increased, can also be improved by subjecting the composition in the austenitic state to an ageing process before the said pretreatment is attempted.
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