Weldable in-situ nano-strengthened rare-earth metal containing aluminum alloy with high strength and toughness and preparation method thereof

A preparation method of a weldable in-situ nano-strengthened rare-earth metal-containing aluminum alloy, the weldable in-situ nano-strengthened rare-earth metal-containing aluminum alloy comprising the following chemical components in mass percentages:

• Zn:
• 5 to 7, Mg:
• 2 to 3, Mn:
• 0.7 to 0.8, Cr:
• 0.1 to 0.2, Cu:
• 0.2 to 0.3, Zr:
• 1.5 to 8, Ti:
• 1.5 to 8, B:
• 0.4 to 5, O:
• 0.2 to 2, Er:
• 0.05 to 0.3, Sc:
• 0.05 to 0.3, Y:
• 0.1 to 0.5, and Al:
• the balance, wherein the weldable in-situ nano-strengthened rare-earth metal-containing aluminum alloy is prepared through composition control, in-situ nano-ceramic particle strengthening and refinement, rare-earth metal microalloying, acoustic magnetic field-controlled compounding, and ultrasonic semi-continuous casting based on an Al—Zn—Mg aluminum alloy as a matrix, to obtain the weldable in-situ nano-strengthened rare-earth metal-containing aluminum alloy comprising nano-Al3(Er+Zr) rare-earth metal-containing precipitated phase, nano-Al3(Sc+Zr) rare-earth metal-containing precipitated phase, and nano-Al3Y rare-earth metal-containing precipitated phase uniformly distributed in grains and a large number of in-situ nano-ZrB2 ceramic particles, in-situ nano-Al2O3 ceramic particles, and in-situ nano-TiB2 ceramic particles distributed at grain boundaries;
• and the preparation method comprises the following specific steps:
• (1) performing an in-situ reaction for in-situ generating the nano-ceramic particles under a control of an acoustic magnetic field;
• (2) after the in-situ reaction is completed, introducing metal elements and rare-earth metals as follows:
• after the in-situ reaction is completed, cooling to 750° C. to 760° C., adding pure Zn, pure Cu, Al—Cr, Al—Mn, Al—Zr, and rare-earth metal-containing intermediate alloys, and conducting a reaction for 10 min to 15 min;
• after the reaction is completed, conducting slagging-off, refining, and degassing;
• and cooling to 680° C., adding pure Mg, and further conducting a reaction for 10 min to 15 min, wherein the rare-earth metals are Sc, Er, and Y;
• (3) preparing an aluminum alloy ingot with uniform components, and a controllable distribution of the nano-ceramic particles in the grains or at the grain boundaries through the ultrasonic semi-continuous casting;
• and
• (4) finally, subjecting the aluminum alloy ingot to homogenization, forming, and a heat treatment to obtain the weldable in-situ nano-strengthened rare-earth metal-containing aluminum alloy.