Analysis of the effect of surface morphology on tensile behavior of LPBF SS316L microstruts

Abstract

The study demonstrates that the presence of sharp notch-like features on the as-built surface of microstruts fabricated via laser powder bed fusion (LPBF) results in reduced mechanical performance under quasi-static tensile loading. 3D models of 250μm diameter cylinders textured with uniform surface features of 25μm, 45μm, 65μm, and 85μm heights were designed to mimic the typical as-built surfaces of LPBF microstruts. Finite element analysis was utilized to simulate the tensile plastic flow interaction with the respective surface morphologies of the microstruts. The localized increase in uniaxial stress at the roots of notches associated with the induced surface features causes an overall strengthening effect in the microstruts, which increases with increasing feature heights. As a result, the ultimate tensile strength increases from 533 MPa for the plain (notch-free) microstrut to a maximum of 760 MPa for the surface textured microstruts. Further, local increase in triaxiality at notch roots restrict plastic flow. As a result, the uniform elongation strain decreases from ∼0.52 for the plain microstrut to a range of 0.36−0.38 for the surface textured microstruts. Post UTS, increasing localization of strain and shifting of maximum triaxiality to notch roots of the surface textured microstruts initiates the final failure.