High-strength molybdenum matrix composites with in-situ Mo2C by graphene addition

Abstract

Molybdenum matrix composites with three different Mo2C contents were developed by in-situ reaction of Mo-graphene using hot pressing sintering at 1700 °C. Microstructure characterization results revealed that micron and submicron Mo2C particles were distributed homogeneously and well bonded with Mo matrix, without cracks or pores in the interface. The well dispersed in-situ Mo2C resulted in matrix grain refinement and significantly reinforced the composites. With increasing content of Mo2C, the hardness of composites was increased gradually. And when the Mo2C content raised above 8.8 vol%, the yield strength was enhanced remarkably. Especially, the microhardness (312 HV0.3) and yield strength (1013 MPa) of Mo matrix composite with 13.7 vol% Mo2C processed by high energy ball milling were 1.6 and 2.8 times that of the pure Mo, respectively. Quantitative analysis of strengthening mechanisms indicated that the high yield strength was attributed to grain refinement and dislocation piling up at the interface between Mo2C particles and Mo matrix. Moreover, the composites with 4.9 vol% and 8.8 vol% Mo2C exhibited noticeably greater strain hardening rates as a result of interaction of dislocations with each other and Mo2C particles.