T-tial alloy-based component comprising areas having a graduated structure

Abstract

The invention relates to a component produced in one piece from an intermetallic γ-TiAl-based alloy with graduated microstructure transition between spatially adjacent areas each of different microstructure structure, which has a lamellar cast microstructure composed of α 2 /γ lamellae in at least one area, and a near-γ microstructure, duplex microstructure or fine-lamellar microstructure in at least one other area, and a transition zone with graduated microstructure, in which the lamellar cast microstructure gradually changes into the other named microstructure, is present between these areas, as well as to a process for its production.

1 . Component produced in one piece from an intermetallic γ-TiAl-based alloy with graduated microstructure transition between spatially adjacent areas each of different microstructure structure, characterized in that it has a lamellar cast microstructure composed of α 2 /γ lamellae in at least one area, and a near-γ microstructure, duplex microstructure or fine-lamellar microstructure in at least one other area, and a transition zone with graduated microstructure, in which the lamellar cast microstructure gradually changes into the other named microstructure, is present between these areas.  
     
     
         2 . Component according to  claim 1 , characterized in that the lamellar cast microstructure composed of α 2 /γ lamellae has been produced by oriented solidification of a melted alloy.  
     
     
         3 . Component according to claims  1  or  2 , characterized in that the near-γ microstructure, duplex microstructure or fine-lamellar microstructure has been produced from the cast microstructure in the at least one other area by massive metal-forming and optionally a post-treatment.  
     
     
         4 . Component according to claims  1 , characterized in that it is a cylindrical semi-finished product, obtained pore-free in bar shape from the melt by means of continuous casting, which is massively metal-formed by extrusion of a bar area.  
     
     
         5 . Component according to claims  1 , characterized in that it is a cylindrical semi-finished product obtained cavity-free from the melt by means of centrifugal casting, which is then massively metal-formed by extrusion of a bar area.  
     
     
         6 . Component according to  claim 1 , characterized in that the alloy corresponds to the empirical formula  
       Ti Al (44-48) (Cr, Mn, V) 0.5-5 (Zr, Cu, Nb, Ta, Mo, W, Ni) 0.1-10 (Si, B, C, Y) 0.05-1    
       expressed in atom-%.  
     
     
         7 . Component according to  claim 1 , characterized in that it is a valve for combustion engines.  
     
     
         8 . Process for the production of components according to  claim 1 , characterized in that a suitable Ti-Al melt is produced in customary manner in a first step, the TiAl melt is converted by oriented solidification in a second step to a semi-finished product which has a lamellar cast microstructure composed of α 2 /γ-TiAl lamellae, and, in a part area or in part areas of the semi-finished product, the lamellar cast microstructure composed of α 2 /γ-TiAl lamellae is converted by massive metal-forming in a third step in a temperature range of 900° C. to 1400° C. to a near-γ microstructure, duplex microstructure or fine-lamellar microstructure.  
     
     
         9 . Process according to  claim 8 , characterized in that a pore-free, cylindrical semi-finished product is produced from the TiAl melt by means of continuous casting, and is then massively metal-formed by extrusion of a bar area.  
     
     
         10 . Process according to  claim 8 , characterized in that a cylindrical semi-finished product is produced cavity-free from the TiAl melt by means of centrifugal casting, and is then massively metal-formed by extrusion of a bar area.  
     
     
         11 . Process according to at least one of  claims 8  to  10 , characterized in that the TiAl alloy corresponds to the empirical formula:  
       Ti A (44-48) (Cr, Mn, V) 0.5-5 (Zr, Cu, Nb, Ta, Mo, W, Ni) 0.1-10 (Si, B, C, Y) 0.05-1    
       expressed in atom-%.  
     
     
         12 . Process according to  claim 8 , characterized in that a valve for combustion engines is produced.