Our goal is to establish the microstructural evolution and mechanical properties to prescribe optimized machine tool parameters for controllability during both additive and subtractive manufacturing. We have a systematic procedure for evaluating the material characteristics of additively manufactured metals, which ranges across traditional single materials and more advanced arrangements of multi-materials, such as 316L stainless steel with C54200 copper [1], maraging steel with CrMn steel [2], and additively manufactured AlSi10Mg on wrought Al6061 [3].

Our microstructural studies involve a series of multi-scale evaluations of the anisotropic additively manufactured metal [4], which include surface topographical characterization by optical microsopy [5], scanning electron microscopy [6], electron backscatter diffraction analysis [7], and transmission electron micropscopy. We also account for the anisotropic mechanical properties through micro-hardness indentation tests [8] and instrumented tensile/compression tests for derivation of finite element method modelling parameters [9].

We evaluate the properties of additively manufactured metals that have undergone various heat treatment processes, such as solution treatment, direct aging, and combinations of the two. Our heat treatment temperatures are primarily derived from international ASTM/ISO standards, but we also have our own contributions with the use of differential scanning calorimetry (DSC) evaluations on phase transition temperatures [10].

Publications

[1] Y. Bai, et al., Dual interfacial characterization and property in multi-material selective laser melting of 316L stainless steel and C52400 copper alloy, Materials Characterization, 167 (2020) 110489.

[2] Y. Bai, et al., Microstructure and mechanical properties of additively manufactured multi-material component with maraging steel on CrMn steel, Materials Science and Engineering: A, 802 (2021) 140630.

[3] C. Zhao, Y. Bai, H. Wang, Feasibility and reliability of laser powder bed fused AlSi10Mg/Wrought AA6061 hybrid aluminium alloy component, International Journal of Precision Engineering and Manufacturing-Green Technology, 10 (2023) 959–977.

[4] Y. Bai, et al., Densification behavior and influence of building direction on high anisotropy in selective laser melting of high-strength 18Ni-CoMo-Ti Maraging Steel, Metallurgical and Materials Transactions A, 51 (2020) 5861–5879.

[5] Y. Bai, et al., Evolution mechanism of surface morphology and internal hole defect of 18Ni300 maraging steel fabricated by selective laser melting, Journal of Materials Processing Technology, 299 (2022) 117328.

[6] C. Zhao, et al., Effect of heat treatment and electroless Ni-P coating on mechanical property and corrosion behaviour of 316L stainless steel fabricated by laser powder bed fusion, Virtual and Physical Prototyping, 19 (2024).

[7] C. Zhao, et al., Influence of scanning strategy and building direction on microstructure and corrosion behaviour of selective laser melted 316L stainless steel, Materials & Design, 209 (2021) 109999.

[8] Y. Bai, et al., Abnormal thermal expansion behaviour and phase transition of laser powder bed fusion maraging steel with different thermal histories during continuous heating, Additive Manufacturinig, 53 (2022) 102712.

[9] Z. Zheng, et al., Microstructure and anisotropic mechanical properties of selective laser melted Ti6Al4V alloy under different scanning strategies, Materials Science & Engineering A, 831 (2022) 142236.

[10] Y. Bai, et al., Effect of heat treatment on the microstructure and mechanical properties of maraging steel by selective laser melting, Materials Science and Engineering: A, 760 (2019) 105–117.

Acknowledgements

This research is proudly supported by the A*STAR Industry Alignment Funds (A-0005203-02-00 and A19E1a0097).