Effects of TiC nanoparticle inoculation on the hot-tearing cracks and grain refinement of additively-manufactured AA2024 Al alloys
Zhaojin Fan, Chun Li, Hailin Yang, Zhilin Liu
Abstract
The hot-tearing cracks and porosities of Al alloys usually developed in the selective laser melting (SLM) additive manufacturing, impairing the corresponding mechanical properties and machining performance. Thus, it is necessary to eliminate these defects via grain refinement of microstructures. In the present work, the SLMed TiC/AA2024 Al alloy was obtained by adding different contents of TiC nanoparticles into the AA2024 Al alloy powder at different laser scanning speeds. Experimental results show that the addition of TiC nanoparticles significantly refined the microstructures of SLMed AA2024 Al alloy matrix. Coarsening columnar grains were gradually transitioned to small equiaxed grains, which suppresses the formation and propagation of cracking and porosities. Such phenomenon was mainly attributed to the significant grain refinement during SLM solidification. The externally added TiC nanoparticles and the in-situ formed Al3Ti particles have certain orientation relationship (ORs) with their surrounding metal matrix. These ORs are related to the nucleating interface with low lattice mismatch, which promotes grain refinement via heterogeneous nucleation.