THE CHANGE IN RESISTIVITY, HARDNESS AND M ICROSTRUCTURE OF BETA-TI-FEBINARY-ALLOYS WITH ACCUMULATIVE ISOCHRONAL AGING

After previous result on the solution treated at 1173K for 3.6ks and w ater quenched(STQ) slate, the beta phase was retained in alloys contai ning more than 4mass% Fe. Resistivity of the 5 similar to 15mass% Fe a lloys showed the negative temperature dependence. The aging behavior o f the quenched Ti-4 similar to 10mass% Fe beta alloys with accumulativ e isochronal aging was investigated by changes in resistivity, hardnes s, and phase constitution which was identified by X-ray diffractometry . The hardness increases by precipitation of isothermal omega phase an d decreases by precipitation of a phase consuming the precipitated ome ga phase. Above 723K, the hardness of the Ti-4 similar to 6mass% Fe al loys became lower than that of STQ state. In 50K/1.8ks accumulative is ochronal aging, the temperature at which precipitation of isothermal o mega phase confirmed by X-ray diffractometry increases with increasing Fe content. On the Ether hand, the influence of Fe content on the tem perature of a phase precipitation is not clear. Precipitation of TiFe can not be detected by the X-ray diffraction in accumulative isochrona l aging up to 773K. The increase of resistivity of Ti-8mass% Fe and Ti -10mass% Fe alloys at room temperature observed in the aging up to 523 K has been attributed to the phase separation in Fe concentration of b eta phase or the precursor of isothermal w phase.