Selective laser melting

Residual stress

Metallurgy

Materials science

Ultimate tensile strength

Machinability

Titanium

Surface roughness

Alloy

Microstructure

Composite material

Acicular

Machining

Titanium alloy

Martensite

Journal of Manufacturing Processes

Due to its vast benefits, Additive Manufacturing (AM) has attracted a great deal of attention during the last two decades. Selective Laser Melting (SLM) is one of the most increasingly used AM techniques in the world. The machinability of SLM-manufactured Ti6Al4V parts in as-built (SLM-AB) and stress-relief (SLM-SR) conditions was studied in this work via toroidal milling. A conventional processed Ti6Al4V alloy was tested as a reference. SLM process parameters for producing near fully dense parts were optimized to yield a volumetric energy density of 46.4 J/mm3. Relative density, microstructure, hardness, residual stresses, surface roughness, cutting forces, tool wear, and chip morphology were evaluated. The SLM-manufactured parts gave a relative density of 99.70 % and higher hardness values than those of the conventional parts by a factor of about 1.2. The conventional, SLM-AB, and SLM-SR Ti6Al4V alloys exhibited microstructures consisting of α and β phases, acicular α′ martensite, α′ martensite and some amounts of α + β phases, respectively. The conventional alloy had the lowest residual stress. SLM-AB had considerable residual tensile stress in the 0° direction of measurement, whereas SLM-SR had the highest compressive stress in both 0° and 90° directions. The lowest cutting force was observed in the conventional alloy and the highest in the SLM-SR alloy. The SLM-AB alloy featured the highest flank wear. However, no significant difference in flank wear was observed in the conventional and SLM-SR alloys.

Machinability of SLM-produced Ti6Al4V titanium alloy parts