System development, formability quality and microstructure evolution of selective laser-melted magnesium

ABSTRACT

A selective laser melting (SLM) system, which consisted of a fibre laser, a three-dimensional motion platform and a motion control system, was developed in this study. The effect of process parameters on the microstructure evolution of SLMed magnesium parts was investigated. The results revealed that under an irradiation of laser energy density <3.0 J/mm, the powder remained in the discrete state. At a laser energy density 3.0–6.0 J/mm, the powder partially melted and sintered together, yielding incompact tracks. As the energy density increased to 6.0–12.0 J/mm, the powder fully melted forming continuous and smooth tracks. With a further increase in the laser energy density evaporation of the powder occurred. Dense magnesium parts free of pores and cracks were successfully fabricated with the optimal energy density of 10.0 J/mm. The immersion experiment revealed that the degradation product was mainly consisted of Mg(OH)₂, which slowed down the degradation rate acting as a protective layer.

KEYWORDS:

• Selective laser melting
• system development
• microstructure
• magnesium
• degradation

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The work was supported by The Natural Science Foundation of China [grant numbers 51575537 and 81572577], Overseas, Hong Kong & Macao Scholars Collaborated Researching Fund of National Natural Science Foundation of China, Hunan Provincial Natural Science Foundation of China [grant numbers 14JJ1006 and 2016JJ1027], the Project of Innovation-driven Plan of Central South University [grant numbers 2015CXS008 and 2016CX023], The Open-End Fund for the Valuable and Precision Instruments of Central South University, The Fundamental Research Funds for the Central Universities of Central South University and the fund of the State Key Laboratory of Solidification Processing in NWPU.