Controlled Interfacial Reactions and Superior Mechanical Properties of High Energy Ball Milled/Spark Plasma Sintered Ti-6Al-4V-Graphene Composite

Ball milling process has become one of the effective methods for dispersing graphene nanoplates (GNPs) uniformly into matrix; however, there are often serious issues of structural integrity and interfacial reactions of GNPs with matrix. Herein, GNPs/Ti-6Al-4V (GNPs/TC4) composites are synthesized using high energy ball milling (HEBM) and spark plasma sintering. Effects of ball milling on microstructural evolution and interfacial reactions of GNPs/TC4 composite powders during HEBM are investigated. As ball milling time increase, particles size of TC4 is first increased (e.g., approximate to 104.15 mu m, 5 h), but then decreased to approximate to 1.5 mu m (15 h), which is much smaller than that of original TC4 powders (approximate to 86.8 mu m). TiC phases are in situ formed on the surfaces of TC4 particles when ball milling time is 10Thinsp;h. GNPs/TC4 composites exhibit 36-103% increase in compressive yield strength and 57-78% increase in hardness than those of TC4 alloy, whereas the ductility is reduced from 28% to 7% with an increase of ball milling time (from 2 to 15 h). A good balance between high strength (1.9 GPa) and ductility (17%) of GNPs/TC4 composites is achieved when the ball milling time is 10 h, attributing to the synergistic effects of grain refinement strengthening, solid solution strengthening, and load transfer strengthening from GNPs and in situ formed TiC.

Automated summary

High energy ball milling and spark plasma sintering were used to synthesize GNPs/TC4 composites, and the effects of ball milling on microstructural evolution and performance were investigated. With increasing ball milling time, the size of TC4 particles initially increased and then decreased, leading to significant improvements in strength and hardness of the composites but reduced ductility. The optimum balance between strength and ductility was achieved at a ball milling time of 10 hours, attributed to synergistic effects of various strengthening mechanisms.