| Budget Amount *help |
¥25,610,000 (Direct Cost: ¥19,700,000、Indirect Cost: ¥5,910,000)
Fiscal Year 2015: ¥3,250,000 (Direct Cost: ¥2,500,000、Indirect Cost: ¥750,000)
Fiscal Year 2014: ¥8,060,000 (Direct Cost: ¥6,200,000、Indirect Cost: ¥1,860,000)
Fiscal Year 2013: ¥14,300,000 (Direct Cost: ¥11,000,000、Indirect Cost: ¥3,300,000)
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| Outline of Final Research Achievements |
This work revealed that ultrafine-grained Ti-6Al-4V alloy (α’-UFG) produced by new type of processing exhibited low-temperature-high-strain-rate superplasticity at the highest level. Herein, dynamic β precipitation from a metastable single α starting microstructure (occurred under deformation) contributed to a stress-accommodation mechanism. Accompanied by this dynamic β-precipitation, grain boundary sliding mode of theα’-UFG dynamically evolved from the type of the Ball-Hutchison model to the type of the Gifkins Core-Mantle model. In addition, high ductility at high temperature is also obtained in the martensite starting microstructure. This is due to the frequent occurrence of dynamic recrystallization during deformation, resulting in enhancement of stress-accommodation and grain-boundary-sliding. Similar behavior has been also confirmed in Ti-6242 alloy. So, formation of metastable starting microstructure was found to be new concept for enhancing the superplastic property.
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