A degree of porosity is expected in additively manufactured (AM) materials. To aid in the qualification of AM materials, the smallest pore size that results in a debit in the… Click to show full abstract
A degree of porosity is expected in additively manufactured (AM) materials. To aid in the qualification of AM materials, the smallest pore size that results in a debit in the fatigue performance is quantified. In the work presented herein, crystal plasticity simulations are used to identify the stress concentration around pores of various sizes, revealing that a single 20-μm pore or two 10-μm pores (with centers spaced 15 μm apart) localize stress at the pore, as opposed to elsewhere in the microstructure. In situ microtomography and far-field high-energy x-ray diffraction microscopy were used to identify crack formation and the evolution of the grain-level micromechanical fields during cyclic loading. Eighteen cracks were observed (15 at pores, 3 at the surface) at highly stressed grains in a sample, although most did not propagate. The dominant crack was seen to originate from the free surface, which is rationalized by fracture mechanics.
               
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