Mechanical Behavior of Additive Manufactured Layered Materials, Part 2: Stainless Steels
MIT Lincoln Laboratory Lexington United States
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Mechanical behavior of two stainless steel alloys produced with Direct Metal Laser Sintering DMLS was measured and is compared to that of similar conventional materials. Flexural modulus measurements were obtained, tensile deformation characterization was performed, and fatigue behavior was investigated in fully reversed bending. Compared to wrought and annealed materials, DMLS 316L demonstrated significantly higher yield strength but similar strain hardening and strain to failure, whereas DMLS 17-4PH exhibited lower yield strength. Fatigue specimens produced additively in the horizontal orientation, such that cyclic stresses were applied in the direction parallel to build planes, displayed fatigue strengths of approximately 85 316L to 95 17-4PH of that of wrought, annealed material. Fatigue behavior was diminished drastically when DMLS specimens fabricated vertically were stressed across the build planes. Vertically-built 316L specimens subjected to hot isostatic pressure demonstrated improved cyclic fatigue strength. In all the additive materials, fatigue cracks initiated at surface defects, internal voids and pre-existing microcracks.
- Metallurgy and Metallography