The invention relates to a method for preparing a heterostructure
magnesium alloy based on low-temperature friction stir additive in the field of
metal processing, and designs a high-quality and high-efficiency cooling tool, which mainly comprises the following steps: firstly, cooling
alcohol to low temperature by using
liquid nitrogen; then the
magnesium alloy plate to be machined is fixed to a cooling tool in a
lap joint mode, and the tool mainly comprises a device body (1), a cooling liquid inflow hole (2), a cooling liquid outflow hole (3), a workpiece containing groove (4), a
liquid storage chamber (5), a pressing plate (6) and fastening screws (7); then low-temperature
alcohol is introduced, an advancing path and technological parameters are set, first-layer stirring friction additive manufacturing is conducted, and in the
machining process, a stirring head and a workpiece are always kept to be submerged in cooling liquid; then, the surface obtained after material adding is milled to be flat, a layer of plate is overlaid on the other unmachined surface again, and the plate is fixed into the workpiece containing groove; and finally, second-layer friction stir additive manufacturing is conducted on the other face of the plate according to the same parameters and the same path. The method can be suitable for additive manufacturing of low-melting-point
metal such as
magnesium alloy and aluminum alloy at the same time, the multi-scale gradient heterostructure
magnesium alloy can be prepared at the same time, the preparation efficiency is improved, and high-quality and low-cost preparation of heterostructure materials is achieved.