Development of Al–Nb–B master alloy with high Nb/B ratio for grain refinement of hypoeutectic Al–Si cast alloys
- 89 Downloads
Al–Nb–B master alloy has been regarded as a promising grain refiner that can reduce grain size of hypoeutectic Al–Si casting alloys. However, its grain refinement performance remains to be improved. In this work, the grain refinement efficacy of Al–Nb–B master alloy is significantly enhanced by modifying the Nb/B ratio through thermodynamic calculation. An Al–Nb–B master alloy with optimum Nb/B ratio of ~ 10:1 provides a fully equiaxed structure across the sections of the Al–10Si and commercial Al–9Si–0.08Ti alloys with an average grain size below 220 μm. The phenomenon is attributed to the existence of NbAl3 and the higher number density of NbB2 at the Nb/B ratio of ~ 10:1, which offers sufficient active nucleating sites to promote the formation of smaller grains. Moreover, the segregation behavior of Si atoms and interfacial energies after doping Si are investigated by first-principles calculations, and the results reveal that Si tends to segregate to the NbAl3/α-Al interface, whereas grain refining potency of NbAl3 for Al remains unchanged. This study has implications for strategic design of Al–Si cast alloy with fine and equiaxed grain structure inoculated by grain refiner.
This work is financially sponsored by the National Natural Science Foundation of China (51871138) and Science and Technology Commission Shanghai Municipality (19010500400). The authors acknowledge Dr. Q.L. Xiao for the FIB test.
JX (1) performed calculation of lattice mismatch f used for the development of the novel Al–Nb–B master alloy; (2) conducted experiments and measurements; and (3) wrote the paper. YL (1) performed thermodynamic calculation of Al–Nb–B system for optimizing Nb/B ratio region and (2) conducted first-principles calculation of heat of segregation and interfacial energy. BH (1) proposed to select a new inoculation system for refining casting Al–Si alloys for high-integrity structural castings and (2) provided commercial Al–9Si–0.08Ti alloy and microscope with polarized light mode. YJ performed TEM investigations. QL (1) designed the research; (2) analyzed the data on optimizing Nb/B ratio of master alloy for grain refinement by adjusting the phase fraction of NbAl3 and number density of NbB2; and (3) wrote the paper with feedback from all co-authors.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
- 21.Nadendla H, Nowak M (2013) Method of refining metal alloys. USA PatentGoogle Scholar
- 37.Hu B, Wang P, Lu Q (2018) Increasing strength of an aluminum alloy. USA PatentGoogle Scholar
- 51.Brandes EA (1983) Smithells metals reference book. Butterworths, LondonGoogle Scholar