Abstract
17-4 precipitation hardening(PH)stainless steel is a multi-purpose engineering alloy offering an excel-lent trade-off between strength,toughness,and corrosion properties.It is commonly employed in additive manufacturing via laser powder bed fusion owing to its good weldability.However,there are remaining gaps in the processing-structure-property relationships for AM 17-4 PH that need to be addressed.For instance,discrepancies in literature regarding the as-built microstructure,subsequent development of the matrix phase upon heat treatment,as well as the as-built residual stress should be addressed to enable reproducible printing of 17-4 builds with superior properties.As such,this work applies a comprehensive characterisation and testing approach to 17-4 PH builds fabricated with different processing parameters,both in the as-built state and after standard heat treatments.Tensile properties in as-built samples both along and normal to the build direction were benchmarked against standard wrought samples in the so-lution annealed and quenched condition(CA).When testing along the build direction,higher ductility was observed for samples produced with a higher laser power(energy density)due to the promotion of interlayer cohesion and,hence,reduction of interlayer defects.Following the CA heat treatment,the austenite volume fraction increased to～35％,resulting in a lower yield stress and greater work hard-ening capacity than the as-built specimens due to the transformation induced plasticity effect.Neutron diffraction revealed a slight reduction in the magnitude of residual stress with laser power.A concentric scanning strategy led to a higher magnitude of residual stress than a bidirectional raster pattern.
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