High strength, combustion-resistant, tube-extrudable aircraft-grade magnesium alloy

Abstract

Embodiments of the invention include magnesium-based alloys especially adapted for extrudable aerospace grade applications. Alloys of the invention provide excellent combinations of mechanical properties, good extrudability in hollow forms, and resistance to combustion.

1 . A magnesium-based extrusion alloy composition comprising, by weight:
 7.0%-11.0% Al, 0.1%-0.8% Zn, 0.15%-0.65% Mn, 0.6%-1.5% Ca, 0.05%-0.6% Y and a balance of Mg and unavoidable impurities.   
     
     
         2 . The alloy according to claim  0  wherein:
 a content of said Mn is between about 0.15 wt % to 0.3 wt % of said alloy. 
 
     
     
         3 . The alloy according to claim  0  wherein:
 a content of said Zn is between about 0.1 wt % to 0.35 wt % of said alloy. 
 
     
     
         4 . The alloy according to claim  0  wherein:
 a content of said Zn is between about 0.4 wt % to 0.6 wt % of said alloy. 
 
     
     
         5 . The alloy according to claim  0  wherein:
 a content of said Al is between about 8.3 wt % to 10 wt % of said alloy. 
 
     
     
         6 . The alloy according to claim  0  wherein:
 a content of said Ca and Y is between about 0.75 wt % to 1.5 wt % of said alloy. 
 
     
     
         7 . The alloy according to claim  0  wherein:
 a total combined content of said Al, Ca, and Y does not exceed 11 wt % of said alloy. 
 
     
     
         8 . An alloy according to  claim 1  wherein:
 said Ca and said Y are provided in intermetallic compounds. 
 
     
     
         9 . The alloy, according to  claim 8 , wherein said intermetallic compounds of Ca and Y comprise: Mg—Al—Ca compounds and Al—Mn—Y compounds, respectively. 
     
     
         10 . The alloy, according to  claim 9 , wherein:
 said Mg—Al—Ca intermetallic compound comprises:   
       up of up to 57 wt % Al and up to 43 wt % Ca. 
     
     
         11 . The alloy, according to  claim 9 , wherein:
 said Al—Mn—Y intermetallic compound comprises 40 wt % Al, 40 wt % Mn and 20 wt % Y.   
     
     
         12 . The alloy according to  claim 9  wherein:
 said Ca and Y intermetallic compounds contribute to flammability resistance of wrought products made from said alloy. 
 
     
     
         13 . The alloy according to claim  0  wherein:
 said alloy comprises Ca in the form of intermetallic particles; said particles having an average diameter of about less than 1 μm and finely distributed within said alloy. 
 
     
     
         14 . The alloy, as claimed in  claim 13 , wherein:
 said intermetallic particles are formed in a wrought process, including extrusion, rolling, or forging.   
     
     
         15 . The alloy, as claimed in  claim 14 , wherein:
 when said alloy is provided in a matrix phase, particles making up said alloy have an average diameter of about 10 μm or less.   
     
     
         16 . The alloy according to  claim 1  wherein:
 said alloy comprises Ca intermetallic particles and said particles make up between about 1.0% to 5.0% of said alloy by volume. 
 
     
     
         17 . The alloy, according to  claim 1 , wherein:
 said alloy has a tensile yield strength of at least 180 MPa and an ultimate tensile strength of at least 270 MPa.   
     
     
         18 . The alloy, according to  claim 1 , wherein:
 said forged or drawn alloy has a tensile yield strength of at least 170 MPa, an ultimate tensile strength of at least 280 MPa and an elongation of at least 7% in tube forms   
     
     
         19 . A method of making a product made from a magnesium-based alloy composition comprising the steps of:
 providing magnesium-based alloy composition comprising, by weight:   7.0%-11.0% Al, 0.1%-0.8% Zn, 0.15%-0.65% Mn, 0.6%-1.5% Ca, 0.05%-0.6% Y and a balance of Mg and unavoidable impurities;
 subjecting said alloy to extrusion wherein billets of said alloy 1 are hydraulically or mechanically forced through an orifice in a die to produce an extruded shape; 
 or subjecting said alloy to rolling wherein billets of said alloy 1 are successively passed through rollers to produce a rolled sheet, plate, or simple shape; 
 or subjecting said alloy to forging wherein billets of said alloy 1 are slowly compressed or quickly impacted with hammers or dies to produce a forged alloy. 
   
     
     
         20 . The method, according to  claim 19 , wherein:
 said extrusion step comprises extruding said alloy into seamless tubes via extrusion of a hollow billet around a mandrel, or into structural tubes via extrusion of solid billets using porthole dies which split metal flow and subsequently merge the metal around a mandrel to form a hollow shape.   
     
     
         21 . The method, according to  claim 19 , wherein:
 said extruded alloy has a tensile yield strength of at least 180 MPa and an ultimate tensile strength of at least 270 MPa.   
     
     
         22 . The method according to  claim 19 , wherein:
 said extruded alloy has a tensile yield strength of at least 170 MPa, an ultimate tensile strength of at least 280 MPa and an elongation of at least 7% in tube forms.   
     
     
         23 . A magnesium-based extrusion alloy composition consisting essentially of, by weight:
 7.0%-11.0% Al, 0.1%-0.8% Zn, 0.15%-0.65% Mn, 0.6%-1.5% Ca, 0.05%-0.6% Y and a balance of Mg and unavoidable impurities.