Effect of TiN nanoparticles on microstructure and properties of Al2024-TiN nanocomposite by high energy milling and spark plasma sintering

Abstract

Ultra-fine grained (UFG) Al2024-TiN nanocomposite was fabricated by high energy milling (HEM) and spark plasma sintering (SPS). The effect of TiN content (1, 2, 3 and 4 wt.%) on the morphology and microstructure of as-milled powders was investigated, as well as on the microstructure and properties of as-SPSed samples. Results show that TiN can accelerate the milling process, solution of Cu atoms and deformation of Al2Cu during milling. Besides, Al grain size of as-milled powders was refined from ∼87 nm to 30–50 nm after TiN was added, staying steady when TiN exceeded 2 wt.%. Moreover, Al2024-2TiN nanocomposite behaved superior comprehensive properties, showing yield and ultimate strength of ∼730 MPa and ∼871 MPa, respectively, which were 185% and 35% higher than those without TiN, and still possessing ∼10% engineering strain. The Al grain sizes of as-SPSed Al2024 and Al2024-2TiN samples were 576.5 nm and 145.4 nm, respectively, exhibiting 6.6 times and 4 times those of their corresponding milled powders. It is suggested that TiN nanoparticles are helpful to refine Al grains during milling and restrain grain growth during sintering. The high strength of Al2024-TiN nanocomposite was mainly attributed to ultra-fine grains, Orowan strengthening and dislocation strengthening due to TiN nanoparticles.