Abstract
Simultaneously improving the strength, toughness, and ductility of cast steels has always been a difficult problem for researchers. Biphase TiCx-TiB2 nanoparticle-reinforced cast steels are prepared by adding in situ nanosized biphase TiCx-TiB2/Al master alloy during the casting process. The experimental results show that a series of significant changes take place in the microstructure of the steel: the ferrite-pearlite structure of the as-cast steels and the bainite structure of the steels after heat treatment are refined, the grain size is reduced, and the content of nanoparticles is increased. Promotion of nucleation and inhibition of dendrite growth by biphase TiCx-TiB2 nanoparticles leads to a refinement of the microstructure. The fine microstructure with evenly dispersed nanoparticles offers better properties [yield strength (1246 MPa), tensile strength (1469 MPa), fracture strain (9.4%), impact toughness (20.3 J/cm2) and hardness (41 HRC)] for the steel with 0.018 wt.% biphase TiCx-TiB2 nanoparticles, which are increased by 15.4%, 31.2%, 4.4%, 11.5%, and 7.9% compared with the 40Cr steels. The higher content of nanoparticles provides higher strengths and hardness of the steel but are detrimental to ductility. The improved properties may be attributed to fine grain strengthening and the pinning effect of nanosized carbide on dislocations and grain boundaries. Through this work, it is known that the method of adding trace (0.018 wt.%) biphase TiCx-TiB2 nanoparticles during casting process can simultaneously improve the strength, toughness, as well as ductility of the cast steel.
Highlights
Solving the problem of simultaneously improving the strength and toughness of cast steels is a long-term goal for researchers
Compared with the 40Cr steel, the yield strength (1246 MPa), tensile strength (1469 MPa), and of the steel containing 0.018 wt.% TiCx -TiB2 nanoparticles are increased by 15.4%, 31.2% and 4.4%, fracture strain (9.4%) of the steel containing 0.018 wt.% TiCx-TiB2 nanoparticles are increased by respectively
Trace biphase TiCx -TiB2 nanoparticle-reinforced steels are innovatively produced by adding nanosized TiCx -TiB2 /Al master alloy during the casting process
Summary
Solving the problem of simultaneously improving the strength and toughness of cast steels is a long-term goal for researchers. TiB2 and TiC-reinforced steel matrix composites were produced through powder metallurgy, improving the wear properties of the composites [18,19,20]. Due to the large difference in specific gravity, agglomeration of nanoparticles and surface pollution of nanoparticles, it seems that the traditional casting method is not suitable for producing nanoceramic-reinforced steel. Because of these constraints, there have been few studies on enhancing the strength and toughness of cast steel with dual-phase nanosized ceramic particles (TiCx -TiB2 ).
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