Sustainable manufacturing of maraging steel seamless tube via flow forming: structure–property relations

Abstract Sustainability in manufacturing is increasingly pushing the metal forming sector to manufacture components with less material wastage. Flow-forming is a sustainable manufacturing route to produce high-value near-net-shape components of complex geometries. The triaxial stress-state and localised deformation occurring during this process necessitates the comprehension of underlying deformation micromechanisms. In this study, flow-forming of MLX ® 19 maraging steel alloy was performed at varying feed rates and the effect on the concomitant microstructural evolution was examined. Increasing the feed rates from 5 to 10 mm/rev resulted in a localised deformation and defects in the flow-formed component. The microstructural features of the outer region of the flow-formed component demonstrated refined and elongated grains while the centre and inner regions exhibited less refined grains. The obtained microstructural heterogeneity was further correlated with the associated governing factors such as the deformation and thermal gradients, as well as strain distribution. Regarding the crystallographic texture evolution, the outer region showed the highest volume fraction (~ 16%) of the rotated Goss component $$\left(011\right)\left[0\overline{1 }1\right]$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mfenced> <mml:mn>011</mml:mn> </mml:mfenced> <mml:mfenced> <mml:mn>0</mml:mn> <mml:mover> <mml:mn>1</mml:mn> <mml:mo>¯</mml:mo> </mml:mover> <mml:mn>1</mml:mn> </mml:mfenced> </mml:mrow> </mml:math> indicating that this region underwent excessive shear deformation in addition to compression. On the other hand, the inner region displayed predominant copper-like $$\left(111\right)\left[0\overline{1 }1\right]$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mfenced> <mml:mn>111</mml:mn> </mml:mfenced> <mml:mfenced> <mml:mn>0</mml:mn> <mml:mover> <mml:mn>1</mml:mn> <mml:mo>¯</mml:mo> </mml:mover> <mml:mn>1</mml:mn> </mml:mfenced> </mml:mrow> </mml:math> and rotated cube $$\left(001\right)\left[\overline{1 }10\right]$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mfenced> <mml:mn>001</mml:mn> </mml:mfenced> <mml:mfenced> <mml:mover> <mml:mn>1</mml:mn> <mml:mo>¯</mml:mo> </mml:mover> <mml:mn>10</mml:mn> </mml:mfenced> </mml:mrow> </mml:math> textures (~ 24.5 and 13.6% respectively) suggesting the fact that the inner region experienced predominantly compressive deformation. Tensile tests confirmed that the flow-formed component demonstrated higher strength and lower ductility compared to the base metal (BM) which was attributed to the dislocation density and refined grain formation.