Investigation of Mechanical Properties and Microstructure Analysis of 5356 Al Alloy Thin Plate and Block Fabricated by Directed Energy Deposition-Arc

Directed Energy Deposition-Arc (DED-Arc) method is popularly being used to produce the near-net-shape products having large structure and complex geometrical features. The repeated heating of previously fabricated layers, during the layer-by-layer deposition of metal in DED-Arc, may result into anisotropy in the mechanical properties and microstructure at different locations. In the present work, the microscopic and mechanical properties of gas metal arc welding-based DED-Arc of material 5356 aluminum alloy thin plate and block are investigated. Microstructural examinations are conducted by optical microscope, energy-dispersive x-ray analysis, scanning electron microscope, and x-ray diffraction analysis. Microscopic examination illustrated that the microstructure has inter-layer and inner layer regions in vertical direction and homogeneous microstructure in horizontal direction of plate and block. Inner and inter-layer regions are also found in the width direction of the block. Macro- and micro-pore are observed in both plate and block samples, and air gaps are present in block samples due to improper penetration between two adjacent layers. alpha-Al and beta-Al3Mg2 second-phase particles are found near the boundary and within the matrix. Mechanical properties are examined by tensile tests and microhardness tests. The average hardness value is found to increase from the bottom region to top the region in both the plate and block. As compared with the casted 5356 Al alloy, the DED-Arc fabricated 5356 Al alloy plate sample has better tensile properties. Block samples showed poor tensile properties due to the presence of more pores and air gaps. The fractures of all the samples collected from both thin plate and block are ductile in nature.