Methods of forming magnesium-based alloys having a bimodal microstructure and magnesium-based alloy components made therefrom

Abstract

Methods of making magnesium-based alloy components are provided. A preform of a magnesium-based alloy having a plurality of zirconium-rich domains distributed in a magnesium-alloy matrix is subjected to a temperature of ≥ about 360° C. and a deformation process that facilitates selective dynamic recrystallization to create a bimodal microstructure in the magnesium-based alloy component having a plurality of un-recrystallized regions distributed in a matrix comprising dynamically recrystallized grains. The magnesium-based alloy includes zinc (Zn) at ≥ about 2 to ≤ about 4 wt. % of the magnesium-based alloy, zirconium (Zr) at ≥ about 0.62 wt. % to ≤ about 1 wt. % of the magnesium-based alloy, total impurities at ≤ about 0.1 wt. % of the magnesium-based alloy, and a balance of magnesium (Mg). Hot-formed magnesium-based alloy components formed from such methods are also contemplated, including automotive components.

What is claimed is: 
     
         1 . A method of making a magnesium-based alloy component comprising:
 casting a magnesium-based alloy by melting a magnesium-based alloy in a furnace having a temperature (T) of greater than or equal to T=650° C.+(500×((C Zr −0.6))° C., where C Zr  represents a concentration of zirconium (Zr) at greater than or equal to about 0.62 wt. % to less than or equal to about 1 wt. % of the magnesium-based alloy, and the magnesium-based alloy further comprises zinc (Zn) at greater than or equal to about 2 to less than or equal to about 4 wt. % of the magnesium-based alloy, total impurities at less than or equal to about 0.1 wt. % of the magnesium-based alloy, and a balance of magnesium (Mg);   solidifying the magnesium-based alloy into a preform comprising a plurality of zirconium-rich domains distributed in grains of a magnesium-alloy matrix; and   subjecting the preform to a temperature of greater than or equal to about 360° C. and a deformation process that facilitates selective dynamic recrystallization to create a bimodal microstructure in the magnesium-based alloy component to form a plurality of un-recrystallized regions distributed in a matrix comprising dynamically recrystallized grains having an average size of greater than or equal to about 0.5 micrometers to less than or equal to about 10 micrometers.   
     
     
         2 . The method of  claim 1 , wherein after the subjecting the preform to the temperature of greater than or equal to about 360° C., a plurality of nanoparticles comprising zirconium and zinc are formed that are precursors to the plurality of un-recrystallized regions formed after the deformation process. 
     
     
         3 . The method of  claim 1 , wherein the subjecting the preform to the temperature of greater than or equal to about 360° C. and the deformation process occur concurrently. 
     
     
         4 . The method of  claim 1 , wherein the casting is conducted at a temperature (T) of greater than or equal to about 700° C. to minimize formation and settling of a plurality of solid particles comprising zirconium in the molten magnesium-based alloy. 
     
     
         5 . The method of  claim 1 , wherein the deformation process is selected from the group consisting of: extruding, forging, flow forming, and combinations thereof. 
     
     
         6 . The method of  claim 1 , wherein the magnesium-based alloy comprises zinc (Zn) at greater than or equal to about 2 to less than or equal to about 3.5 wt. % of the magnesium-based alloy and zirconium (Zr) at greater than or equal to about 0.65 wt. % to less than or equal to about 0.8 wt. % of the magnesium-based alloy. 
     
     
         7 . The method of  claim 1 , wherein the magnesium-based alloy comprises zinc (Zn) at greater than or equal to about 2 wt. % to less than or equal to about 2.5 wt. % of the magnesium-based alloy and zirconium (Zr) at greater than or equal to about wt. % to less than or equal to about 0.8 wt. % of the magnesium-based alloy. 
     
     
         8 . The method of  claim 1 , wherein the magnesium-based alloy component has the plurality of un-recrystallized regions homogeneously distributed in the matrix. 
     
     
         9 . The method of  claim 1 , wherein the plurality of un-recrystallized regions occupy greater than or equal to about 15% by area to less than or equal to about 40% by area of the magnesium-based alloy component and the plurality of un-recrystallized regions has an average equivalent diameter of greater than or equal to about 10 micrometers to less than or equal to about 100 micrometers. 
     
     
         10 . The method of  claim 1 , wherein at least one region of the magnesium-based alloy component has a yield strength of greater than or equal to about 170 MPa and an elongation of greater than or equal to about 15%. 
     
     
         11 . The method of  claim 1 , wherein at least one region of the magnesium-based alloy component has a yield strength of greater than or equal to about 185 MPa and has an elongation of greater than or equal to about 20%. 
     
     
         12 . The method of  claim 1 , wherein the magnesium-based alloy component is an automotive component. 
     
     
         13 . A hot-formed solid magnesium-based alloy component comprising:
 a bimodal microstructure having a plurality of un-recrystallized domains distributed in a matrix comprising dynamically recrystallized grains having an average size of greater than or equal to about 0.5 micrometers to less than or equal to about 10 micrometers, wherein a magnesium-based alloy comprises zinc (Zn) at greater than or equal to about 2 to less than or equal to about 4 wt. % of the magnesium-based alloy, zirconium (Zr) at greater than or equal to about 0.62 wt. % to less than or equal to about 1 wt. % of the magnesium-based alloy, total impurities at less than or equal to about 0.1 wt. % of the magnesium-based alloy, and a balance of magnesium (Mg).   
     
     
         14 . The hot-formed solid magnesium-based alloy component of  claim 13 , wherein the magnesium-based alloy comprises zinc (Zn) at greater than or equal to 2 to less than or equal to about 3.5 wt. % of the magnesium-based alloy and zirconium (Zr) at greater than or equal to about 0.65 wt. % to less than or equal to about 0.8 wt. % of the magnesium-based alloy. 
     
     
         15 . The hot-formed solid magnesium-based alloy component of  claim 13 , wherein the magnesium-based alloy comprises zinc (Zn) at greater than or equal to about 2 wt. % to less than or equal to about 2.5 wt. % of the magnesium-based alloy and zirconium (Zr) at greater than or equal to about 0.65 wt. % to less than or equal to about 0.8 wt. % of the magnesium-based alloy. 
     
     
         16 . The hot-formed solid magnesium-based alloy component of  claim 13 , wherein the plurality of un-recrystallized domains is homogeneously distributed in the matrix, wherein the plurality of the plurality of un-recrystallized domains occupy greater than or equal to about 15% by area to less than or equal to about 40% by area of the hot-formed solid magnesium-based alloy component, and the plurality of un-recrystallized domains has an average equivalent diameter of greater than or equal to about 10 micrometers to less than or equal to about 100 micrometers. 
     
     
         17 . The hot-formed solid magnesium-based alloy component of  claim 13 , wherein at least one region of the hot-formed solid magnesium-based alloy component has a yield strength of greater than or equal to about 170 MPa and an elongation of greater than or equal to about 15%. 
     
     
         18 . The hot-formed solid magnesium-based alloy component of  claim 13 , wherein at least one region of the hot-formed solid magnesium-based alloy component has a yield strength of greater than or equal to about 185 MPa and has an elongation of greater than or equal to about 20%. 
     
     
         19 . The hot-formed solid magnesium-based alloy component of  claim 13 , wherein the hot-formed solid magnesium-based alloy component is an automotive component. 
     
     
         20 . The hot-formed solid magnesium-based alloy component of  claim 13 , wherein the hot-formed solid magnesium-based alloy component is a wheel.