mg-zn-cu-zr-(cr-ca) alloy under gpa level high pressure and its preparation method

Abstract

The invention provides Mg-Zn-Cu-Zr-(Cr-Ca) alloy under the GPa level high pressure effect and a preparation method. A six-side ejecting hydraulic press is adopted to solidify the Mg-Zn-Cu-Zr-(Cr-Ca) alloy under the 2GPa-6GPa high pressure effect. The solidification structure characteristics, distribution of solute elements such as Zn, Cu and Ca, heterogeneous nuclei in high-pressure solidification, and strengthening and toughening mechanism are researched with the EBSD, SEM and other analytical methods. The results show that primary crystal alpha-Mg of the high pressure solidified alloy is regular isometric crystal. The average grain size is refined from 186[mu]m at the normal pressure to 22[mu]m at 6GPa. The solid solubility of Zn in the alpha-Mg matrix increases from 3.63% under the normal pressure to 6.23% under 6GPa. Intercrystalline second phase gradually changes from a network under the normal pressure to a discontinuous island or granular distribution under 6GPa. MgZn2, Mg2Ca and Cr2Zr phases are alpha-Mg crystal high-effective heterogeneous nuclear substrate in high-pressure solidification process. The number of crystal nucleus in the solidification process is greatly increased. The strength of the alloy increases with the increase of solidification pressure. Maximum resistance increases from 240MPa under atmospheric pressure to 520MPa under 6GPa during crushing.

Description

technical field [0001] The invention belongs to the technical field of Mg-Zn-Cu alloys, and relates to a Mg-Zn-Cu-Zr-(Cr-Ca) alloy under the action of GPa level high pressure and a preparation method. Background technique [0002] Mg-Zn-Cu alloy is a relatively successful Mg-Zn heat-resistant alloy in commercial application so far. Since Cu exists in the eutectic phase Mg(Zn,Cu) 2 Among them, it has better high temperature performance below 150°C, and can be used in automotive engine parts and propellers. However, the cast Mg-Zn-Cu alloys reported publicly have coarse as-cast structures, and the main strengthening phase Mg(Zn,Cu) 2 The eutectic phase is multi-linked into a network and distributed between dendrites, not only Mg(Zn,Cu) 2 The strengthening effect of the phase cannot be fully exerted, and the mechanical properties of the cast Mg-Zn-Cu alloy will also be reduced. Therefore, in order to further improve the mechanical properties of Mg-Zn-Cu alloy and expand its...

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Problems solved by technology

According to the existing high-pressure solidification theory, the pressure always reduces the activation energy of nucleation and increases the nucleation rate; inhibits the diffusion of atoms and increases the activation energy of atomic diffusion, thereby increasing the activation energy of crystal growth and reducing the crystal growth rate

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