In situ phase interface engineering of MoLa alloys for enhanced strength

Incoherent interphases and oxygen segregation at the grain boundaries (GBs) significantly deteriorate the strength of Mo-based alloys. In this study, a new additive, LaB 6 , was proposed to enhance the mechanical properties . It was found that LaB 6 reacted with the matrix to generate coherent La 2 O 3 , volatile B 2 O 3 and tiny MoB in situ during sintering. The addition of LaB 6 does not increase strength by itself, but can limit grain growth and construct a coherent interface between the as-obtained La 2 O 3 and Mo matrix. More importantly, the oxygen impurity is removed by B in the form of B 2 O 3 , which purifies the GBs. As a result, the as-sintered Mo-La-B billets present an extremely high ultimate tensile strength of 965 MPa, which is among the best recorded values for all sintered Mo-based alloys. The enhanced strength can be attributed to the refined grain size, coherent phase interface , and purified GBs.