1. A preparation method for nano-porous FePt alloys with strong permanent magnetism comprising:(1) precursor alloys ingots are prepared using electric arc melting or high-frequency induction melting under an Ar atmosphere;
(2) amorphous or amorphous+nanocrystalline alloy ribbons are prepared using a single-roller melt-spinning technology, and a thickness and phase structure of the ribbons are controlled by a rotational speed of a copper roller;
(3) precursors containing uniformly distributed nano-composite phases of hard magnetic L10-FePt and soft magnetic Fe2B are directly obtained by melt-spinning or obtained by conducting vacuum annealing on the melt-spun ribbon samples;
(4) by taking the precursor as a working electrode, Ag/AgCl as a reference electrode, and an acid solution with a H+concentration of 0.02-1.0 mol/L as an electrolytic solution, dealloying is conducted using electrochemical technique under constant voltages of ?0.28-1.5 V, phases mainly including soft magnetic Fe2B except hard magnetic L10-FePt are selectively dissolved, and nano-porous FePt alloys with permanent magnetism containing a single L10-FePt phase are prepared;
the nano-porous FePt alloys with strong permanent magnetism, wherein the nano-porous alloys are composed of ordered hard magnetic of L10-Fe-Pt phase and have a chemical composition of FewCoxPtyPdz, w, x, y and z respectively representing atomic percent of each corresponding element in the expression, where 25?w?55, 0?x?25, 45?w+x?55, 45?y?55, 0?z?10, 45?y+z?55, and w+x+y+z=100;
the nano-porous alloys are prepared from the precursor alloys through a dealloying technique, and have an integrated doubly-connected nano-porous structure with pore sizes of 10-50 nm, and ligament thicknesses of 20-80 nm;
an expression of the composition of the precursors for preparing the nano-porous alloys is FeaCobPtcPddBeCfPgSih, a, b c, d, e, f, g and h respectively representing atomic percent of each corresponding element in the expression, where 30?a?70, 0?b?30, 40?a+b?70, 8?c?40, 0?d?5, 8?c+d?40, 10?e?35, 0?f?5, 0?g?5, 0?h?3, 10?e+f+g+h?35, and a+b+c+d+e+f+g+h=100, and
the nano-porous FePt alloys with strong permanent magnetism has strong permanent magnetism: under an applied magnetic field of 50 kOe, a coercivity is 13.4-18.5 kOe, a magnetization is 40.4-56.3 emu/g, and a remanence is 28.3-37.4 emu/g.