Development of Mo alloys with improved resistance to embrittlement by recrystallization and irradiation

In order to overcome the recrystallization embrittlement and irradiation embrittlement in Mo and W, which are major problems for their fusion applications, the basic idea of alloy design and microstructure control was presented. By applying the idea to Mo, ultra-fine grained Mo alloys with very fine TiC particles mostly existing at grain boundaries were developed for TIC additions of 0.1 to 1.0 wt%. Impact three-point bending tests showed that before and after recrystallization and fast-neutron irradiations to 0.08 dpa the developed alloys exhibit much lower ductile-brittle transition temperature (DBTT) and higher strength than TZM. The developed alloys also showed much higher resistance to recrystallization and grain growth. Both resistance increased with increasing TiC content; in the irradiated state the 1.0 wt% TiC-added alloy showed a DBTT lower by more than 200 K than TZM. The cause of the observed improvement was discussed.