METHOD FOR MODIFYING ALLOY FOR STRUCTURAL MEMBER PROVIDED WITH METASTABLE PHASE

摘要

PURPOSE:To obtain a high strength member in which the metallic structure of a stable phase is made fine-grained and having stabilized properties by subjecting a structural member in which its phase is transformed into a stable one by specific calorific value or above at the time of heating at a specified temp. rising rate to heat treatment at a specified temp. and slowing the above transformation. CONSTITUTION:An alloy for a structural member provided with a semistable phase transforming into a semistable one at a phase transforming temp. by =20J/g calorific value after heating at 40 deg.C/min heating rate is subjected to heat treatment at a temp. lower than the temp. Tp. Then, =50% of the semistable phase of this alloy is transformed into a stable one having a fine grain structure. In the case of an alloy having 20J/g calorific value, its strength is relatively low, its metallic structure is coarsened by the above heating treatment and the strength is furthermore deteriorated. Moreover, in the case of 50% transforming ratio from the semistable phase into a stable one, a tendency that the properties of the alloy is made unstable is shown.