Study On Microstructures And Mechanical Properties Of Bulk Ultrafine-Grained AlTiB Alloy Materials Prepared By Equal Channel Angular Processing

The AlTiB master alloy is a good grain refiner for Aluminum and its Alloys. However, there are also some quality problems at present. For example, the large grain size of TiAl₃ which exist in AlTiB master alloy as second phases will reduce the effectiveness of grain refinement.Equal Channel Angular Processing (ECAP) technique has been proved to be an effective method for the fabrication of various bulk ultrafine-grained materials. Subjected to intense plastic straining in a die for ECAP, the sample can obtain Micrometer-sized or Nanometer-sized microstructure.The deformation force was calculated. And the die for ECAP was designed and manufactured. Subsequently, the AlTiB master alloy samples were pressed through the die at room-temperature. The main factors for the grain refinement, and the distortion behavior of second phase were discussed in detail. Shear performance, microstructure development and property characteristic of the AlTiB master alloy materials were researched by X-ray diffraction device, optical microscope and scan electronic microscope. In the paper, an ultrafine-grained material of AlTiB alloy which average grain size was 5μm has been fabricated. This wills broad the application range of AlTiB alloy. The yield strength increase 69.4 % with the number of 142.0MPa before ECAP and 240.5MPa after 8 passes. In addition, the Vickers-hardness has also greatly improved.According to analysis, it concluded that the rigid TiAl₃ particle can shear the matrix of AlTiB alloy. This helps to grain refinement. The distortion behavior of second-phase was also preliminary research. Responding to shearing force during ECAP process, dislocation movement leads to stress concentration, and then induces tiny crack around the second TiAl₃.