Evolution of secondary phase particles during deformation of Al-5Ti-1B master alloy and their effect on α-Al grain refinement

Hong Yu¹，Ning Wang²，Renguo Guan^1,2，Di Tie²，Zheng Li¹，Yanan An¹，Yang Zhang²

1. State Key Laboratory of Solidification Processing,Center of Advanced Lubrication and Seal Materials,School of Materials Science and Engineering,Northwestern Polytechnical University2. School of Materials Science and Engineering,Northeastern University

摘 要：Addition of Al-5Ti-1B alloy to molten aluminum alloys can refine α-Al grains effectively and thereby improve their strength and toughness. TiAl₃ and TiB₂ in Al-5Ti-1B alloy are the main secondary-phase particles for refinement, while the understanding on the effect of their sizes on α-Al grain refinement continues to be fragmented. Therefore, Al-5Ti-1B alloys with various sizes and morphologies of the secondary-phase particles were prepared by equal channel angular pressing（ECAP）. Evolution of the secondary-phase particles during ECAP process and their impact on α-Al grain refinement were studied by X-ray diffraction and scanning electron microscope（SEM）. Results show that during the ECAP process, micro-cracks firstly appeared inside TiAl₃ particles and then gradually expanded, which resulted in continuous refinement of TiAl₃ particles. In addition, micro-distribution uniformity of TiB₂ particles was improved due to the impingement of TiAl₃ particles to TiB₂ clusters during deformation. Excessively large sizes of TiAl₃ particles would reduce the number of effective heterogeneous nucleus and thus resulted in poor grain refinement effectiveness. Moreover, excessively small TiAl₃ particles would reduce inhibitory factors for grain growth Q and weaken grain refinement effectiveness. Therefore, an optimal size range of 18-22 μm for TiAl₃ particles was suggested.

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