Multi-response optimization of SLM-produced Ti6Al4V alloy: focusing on density and surface roughness

This paper investigates the impact of the selective laser melting (SLM) technique on variables on roughness of surface and density. Grey relational analysis, as a multi-response optimization method, was employed to determine an ideal set of processing parameters for achieving the highest relative density and the lowest surface roughness. An experimental design using Taguchi L9 orthogonal array was conducted, focusing on scanning speed (v\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$v$$\end{document}), laser power (P\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$P$$\end{document}), and hatch spacing (h\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$h$$\end{document}). The results revealed that the optimal process parameters were P\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$P$$\end{document}: 200 W, v\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$v$$\end{document}: 1000 mm/s, and h\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$h$$\end{document}: 0.08 mm, which led to a relative density of 99.86% (4.4238 g/cm3) and a surface roughness of 16.41 mu m. Analysis of variance (ANOVA) and regression analysis were used to evaluate the contribution of each parameter, among the examined parameters, scanning speed emerged as the most influential, with hatch spacing and laser power following in importance. Validation experiments confirmed the reliability of the optimization results through optical microscopy and surface profile analyses. Microstructural characterization of the as-built samples revealed a typical SLM-induced morphology consisting of fine acicular alpha ' martensite within prior beta-phase grains, indicating a high cooling rate solidification. The microstructure exhibited a columnar growth pattern aligned along the build direction, with minimal porosity, supporting the high relative density achieved. The findings demonstrate a statistically significant relationship between process parameters and the quality indicators, offering valuable insights for optimizing SLM-produced Ti6Al4V components.