INFLUENCE PROCESSING PARAMETERS ON THE MICROSTRUCTURE OF

ODS ALLOYS

DiscussionJan Hoffmann

2nd ODISSEUS Workshop 2015

What are desired microstructures?

What are desired microstructures?

Free of texture?

Ultra fine grains?

Cold deformed?

What are desired microstructures?

Free of texture?

Ultra fine grains?

Cold deformed?

Considering that the size and density of nano-particles are similar, the low creep resistance of 9Cr-ODS relative to that of 12Cr-ODS is thought to be due to small grains which can accelerate grain boundary-induced deformation at relatively low applied stress. T. Muroga et al., Fus Eng. Des 89 (2014)

What are desired microstructures?

Free of texture?

Ultra fine grains?

Cold deformed?

Considering that the size and density of nano-particles are similar, the low creep resistance of 9Cr-ODS relative to that of 12Cr-ODS is thought to be due to small grains which can accelerate grain boundary-induced deformation at relatively low applied stress. T. Muroga et al., Fus Eng. Des 89 (2014), Japan

[9%Cr-ODS] Under long-term thermal aging at 973 K, the fraction of low misorientation angles remained unaffected after aging up to 5000 h and only minor decrease after up to 10,000 h. Yanfen Li et al. JNM 255 (2014)

Main influences?

Main influences?

Mechanical alloying?

Compaction?

TMT

Main influences?

Mechanical alloying?

Compaction? TMT

…a significant dissolution of Y into the crystalline iron matrix at these milling times [60 hours] was highly unlikely. Hilger et. al JNM 447 (2014), HZDR

Main influences?

Mechanical alloying? Compaction? TMT

“….all TMT methods refined the grain size, increased dislocation density and ensured improved tensile and impact fracture properties” , Oksiuta et al. JNM 451 (2014), PSI

“…the detailed behaviors of phase transformation, dislocation recovery, and diffusion during the repeated hot-rolling treatment are not understood well.”, Thak Sang Byun et al. JNM 449 (2014), ORNL

Main influences?

Mechanical alloying? Compaction? TMT

“….all TMT methods refined the grain size, increased dislocation density and ensured improved tensile and impact fracture properties” , Oksiuta et al. JNM 451 (2014), PSI

“…the detailed behaviors of phase transformation, dislocation recovery, and diffusion during the repeated hot-rolling treatment are not understood well.”, Thak Sang Byun et al. JNM 449 (2014), ORNL

Taylored ODS alloys?

Taylored ODS alloys?Control of:

ODS-Particle size/density/distribution

Taylored ODS alloys?Control of:

ODS-Particle size/density/distribution

Grain size

Taylored ODS alloys?Control of:

ODS-Particle size/density/distribution

Grain size

Cold work during TMT

THANK YOU FOR THE DISCUSSION!