Experimental investigation of mechanical properties of the AISI 316L stainless steel: macro- and microscale

Additive manufacturing (AM) has recently gained popularity over the conventional manufacturing methods as it allows for innovative design solutions in terms of geometric complexity and shape optimization. As a result of the geometry, size and heterogeneous microstructure of the AM samples, conventional macroscale experiments are, however, frequently inadequate in determining the resulting material parameters. In such cases, nanoindentation represents a viable non-destructive technique for determining the mechanical properties such as Young's modulus (EIT) and hardness (HIT) of small samples' volumes. The nanoindentation measurements on a Keysight G200 machine equipped with a standard Berkovich tip are performed in this study on AISI 316L wrought samples as well as samples obtained via the laser-powder bed fusion (L-PBF) AM process. The standard depth-controlled loadingunloading method is used. With the aim of comparing the material properties on the macro- and microscale, conventional monotonic uniaxial tensile tests are also performed on both samples types. The possibility of calibrating the material parameters of finite element (FE) numerical models using nanoindentation test results to obtain the load vs. the indentation depth curve is finally discussed. Experimentally obtained load-displacement curves are used to calibrate the elastic and plastic material parameters of the FE model. Since FE modelling of the nanoindentation process is a nonlinear elasto-plastic contact problem, Young's modulus and hardness alone are, in fact, not sufficient to characterize properly the overall material behaviour.