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, LaB6, was proposed to enhance the mechanical properties. It was found that LaB6 reacted with the matrix to generate coherent La2O3, volatile B2O3 and tiny MoB in situ during sintering. The addition of LaB6 does not increase strength by itself, but can limit grain growth and construct a coherent interface between the as-obtained La2O3 and Mo matrix. More importantly, the oxygen impurity is removed by B in the form of B2O3, 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.