Crystallographic Texture and Substructural Phenomena in 316 Stainless Steel Printed by Selective Laser Melting

Area of Science:

• Materials Science
• Additive Manufacturing
• Metallurgy

Background:

• Selective Laser Melting (SLM) is gaining traction for metal additive manufacturing.
• Understanding SLM-printed 316 stainless steel (SS316) properties is crucial but limited due to complex process variables.
• Existing literature shows conflicting findings on SS316 crystallographic textures and microstructures.

Purpose of the Study:

• To investigate the crystallographic textures and microstructures of SLM-printed SS316.
• To clarify discrepancies in reported findings regarding SLM-processed SS316.
• To analyze the stability and impact of microstructural features after heat treatment.

Main Methods:

• Characterization of as-printed SS316 using techniques to analyze crystallographic texture and microstructure.
• Investigation of microstructural features, including columnar/cellular structures and inclusions.
• Analysis of material stability and behavior after annealing (ASM solution treatment) at 1050 °C.

Main Results:

• As-printed SS316 exhibits macroscopic asymmetry in structure and crystallographic texture.
• Specific crystallographic directions (<101>, <111>) align with SLM scanning and build directions.
• Identified non-crystallographic low-angle boundary features aligned with the laser scanning direction.
• Observed 500 ± 200 nm columnar/cellular features composed of dislocations and enriched inclusions.
• These nanoscale features remained stable after 1050 °C solution treatment, hindering recrystallization and grain growth.
• Large 2-4 μm inclusions with heterogeneous chemical and phase distribution formed during solution treatment.

Conclusions:

• SLM-printed SS316 possesses unique, asymmetric crystallographic and microstructural characteristics.
• Nanoscale features, stabilized by inclusions, effectively impede high-temperature grain boundary migration.
• The inherent stability of these nanoscale structures at elevated temperatures has significant implications for material performance.