Methods of preparing heat resistant, creep-resistant aluminum alloy

Abstract

A heat-resistant, creep-resistant aluminum alloy containing from 10 to 30 mass % of silicon, from 3 to 10 mass % of at least either iron or nickel in total, from 1 to 6 mass % of at least one rare earth element in total, and from 1 to 3 mass % of zirconium, preferably excluding titanium, magnesium and copper, with the rest substantially consisting of aluminum, is prepared by a method including providing a rapidly cooled aluminum alloy powder, molding the powder into a pressurized powder compact, and performing hot plastic working on the compact to form a product shape such as a billet. The compact is exposed to a temperature of at least 450° C. for at least 10 seconds and not more than 30 minutes before forming the product shape by the hot plastic working.

What is claimed is:  
     
         1 . A method of preparing a heat-resistant, creep-resistant aluminum alloy containing at least 10 mass % and not more than 30 mass % of silicon, at least 3 mass % and not more than 10 mass % of at least either iron or nickel in total, at least 1 mass % and not more than 6 mass % of at least one rare earth element in total and at least 1 mass % and not more than 3 mass % of zirconium with the rest substantially consisting of aluminum, 
 comprising a step of molding rapidly cooled alloy powder consisting of an aluminum alloy into a pressurized powder compact ( 1   a ) and thereafter working said pressurized powder compact ( 1   a ) into a product shape (1c) by hot plastic working, wherein    the time exposing said pressurized powder compact ( 1   a ) not yet worked into said product shape (1c) to a temperature of at least 450° C. is at least 15 seconds and within 30 minutes.    
     
     
         2 . The method of preparing a heat-resistant, creep-resistant aluminum alloy according to  claim 1 , performing solidification by hot plastic working at a rate of change of at least 60% in average area of a section perpendicular to a pressurization axis for working said pressurized powder compact ( 1   a ) into said product shape (1c).  
     
     
         3 . The method of preparing a heat-resistant, creep-resistant aluminum alloy according to  claim 1 , wherein said hot plastic working includes a step of performing solidification by hot forging.  
     
     
         4 . The method of preparing a heat-resistant, creep-resistant aluminum alloy according to  claim 1 , wherein said step of working said pressurized powder compact ( 1   a ) into said product shape ( 1   c ) by said hot plastic working includes steps of: 
 performing first heat treatment on said pressurized powder compact ( 1   a ) at a temperature of at least 420° C. and not more than 550° C.,    performing powder forging on said pressurized powder compact ( 1   a ) subjected to said first heat treatment thereby obtaining a powder-forged body ( 1   b ),    performing second heat treatment on said powder-forged body ( 1   b ) at a temperature of at least 400° C. and not more than 550° C., and working said powder-forged body ( 1   b ) subjected to said second heat treatment into said product shape (1c) by shape forging.    
     
     
         5 . The method of preparing a heat-resistant, creep-resistant aluminum alloy according to  claim 1 , wherein said step of working said pressurized powder compact ( 1   a ) into said product shape ( 1   c ) by said hot plastic working includes steps of: 
 performing heat treatment on said pressurized powder compact ( 1   a ) at a temperature of at least 450° C. and not more than 550° C.,    performing powder forging on said pressurized powder compact ( 1   a ) subjected to said heat treatment thereby obtaining a powder-forged body ( 1   b ), and    working said powder-forged body ( 1   b ) into said product shape ( 1   c ) by shape forging.    
     
     
         6 . The method of preparing a heat-resistant, creep-resistant aluminum alloy according to  claim 1 , wherein said step of working said pressurized powder compact ( 1   a ) into said product shape ( 1   c ) by said hot plastic working further includes steps of: 
 performing heat treatment on said pressurized powder compact ( 1   a ) at a temperature of at least 450° C. and not more than 550° C., and    working said pressurized powder compact ( 1   a ) subjected said to heat treatment into said product shape ( 1   c ) by powder shape forging.    
     
     
         7 . The method of preparing a heat-resistant, creep-resistant aluminum alloy according to  claim 1 , wherein said step of working said pressurized powder compact ( 1   a ) into said product shape ( 1   c ) by said hot plastic working includes steps of: 
 performing first heat treatment on said pressurized powder compact ( 1   a ) at a temperature of at least 420° C. and not more than 550° C.,    performing extrusion on said pressurized powder compact ( 1   a ) subjected to said first heat treatment thereby obtaining an extruded body ( 1   b ),    cutting said extruded body ( 1   b ),    performing second heat treatment on cut said extruded body ( 1   b ) at a temperature of at least 400° C. and not more than 550° C., and    working said extruded body ( 1   b ) subjected to said second heat treatment into said product shape ( 1   a ) by shape forging.    
     
     
         8 . A method of preparing a billet ( 1   b ) of a heat-resistant, creep-resistant aluminum alloy containing at least 10 mass % and not more than 30 mass % of silicon, at least 3 mass % and not more than 10 mass % of at least either iron or nickel in total, at least 1 mass % and not more than 6 mass % of at least one rare earth element in total and at least 1 mass % and not more than 3 mass % of zirconium while containing none of titanium, magnesium and copper, with the rest substantially containing aluminum, 
 comprising a step of molding rapidly cooled alloy powder consisting of an aluminum alloy into a pressurized powder compact ( 1   a ) and thereafter performing hot plastic working on said pressurized powder compact ( 1   a ) thereby forming a billet ( 1   b ), wherein    the time exposing said pressurized powder compact ( 1   a ) to a temperature of at least 450° C. before forming said billet ( 1   b ) is at least 10 seconds and within 20 minutes.