Nd2Fe14C-based magnet with better permanent magnetic properties prepared by a simple mechanochemical method

•HEBM in heptane, Nd-Fe alloy disproportionates into NdH2+δ, α-Fe and Fe3C.•Annealed to 850°C in vacuum, NdH2+δ decomposes and Nd2Fe14C phase is formed.•The H and C atoms come from the decomposition of heptane.•Adding B to Nd-Fe promotes the formation of Nd2Fe14C and suppresses Nd-C and α-Fe.