Aluminum-alloy ingot and manufacturing method thereof

Abstract

An aluminum-alloy ingot contains TiB2 aggregates (2) dispersed in an aluminum matrix (1). The TiB2 aggregates (2) are formed by aggregation of TiB2 particles (3). The average value of the circle-equivalent diameters of the TiB2 aggregates (2) in the state in which the TiB2 aggregates (2) are exposed at a surface of the aluminum matrix (1) is 3.0 μm or less and the average value of the circularities is 0.20 or more.

1 . An aluminum-alloy ingot comprising:
 an aluminum matrix; and   TiB 2  aggregates, which are dispersed in the aluminum matrix and are formed of aggregated TiB 2  particles;   wherein the average value of the circle-equivalent diameters of the TiB 2  aggregates in the state in which the TiB 2  aggregates are exposed from the aluminum matrix is 3.0 μm or less and the average value of the circularities is 0.20 or more.   
     
     
         2 . The aluminum-alloy ingot according to  claim 1 , wherein the content of the TiB 2  aggregates in the aluminum matrix is 0.0001 mass % or more and 0.0010 mass % or less based on the boron atoms. 
     
     
         3 . A method of manufacturing the aluminum-alloy ingot according to  claim 1 , comprising:
 melting a crystal-grain refining agent, which contains TiB 2  particles in a base composed of aluminum and has an average value of center-to-center distances between adjacent TiB 2  particles in an arbitrary cross section that is 0.60 μm or more, in a melt of aluminum alloy; and   after the melting step, casting the melt.   
     
     
         4 . A method of manufacturing the aluminum-alloy ingot according to  claim 1 , comprising:
 melting a crystal-grain refining agent, which contains TiB 2  particles in a base composed of aluminum in which the TiB 2  particles are aggregated, in a melt of an aluminum alloy; and   after the melting step, casting the melt;   wherein, when projection-surface areas of 2,000 or more TiB 2  aggregates are measured in the state in which TiB 2  aggregates are exposed from the base, the TiB 2  aggregates in the crystal-grain refining agent have a particle-size distribution in which the average value of the circle-equivalent diameters of TiB 2  aggregates, which have a projection-surface area in the 95 th  percentile or higher, is 3.0 μm or less.   
     
     
         5 . The method of manufacturing the aluminum-alloy ingot according to  claim 3 , wherein the melt is cast within 30 min after the crystal-grain refining agent has been melted in the melt.