Development of Microstructural Control for Laser-PBF Ti-6Al-4V

Ti-6Al-4V is widely used in the aerospace industry because of its high specific strength, excellent heat resistance and corrosion resistance. On the other hand, the manufacturing cost is higher than other alloys due to its high cutting and material cost. AM (Additive Manufacturing), which can provide them with enhanced functionality through high flexibility of design and improvement of material yield by near-net shape, is expected to be a solution to the above problem. In particular, the Laser-PBF (Powder Bed Fusion) method enables high-precision building of complex shapes, so this method is being applied to products.<br/> <br/>However, since process of AM is a new technology, there are many unclear points regarding the relationship between manufacturing conditions, quality, and mechanical properties, and it is important to clarify the fundamental phenomena in order to obtain stable material properties. The purpose of this study is to control material properties of additive manufactured Ti-6Al-4V. The test specimens were built by L-PBF method under several conditions of process parameters (power, scan speed, hatch spacing, layer thickness). Also, we clarified the thermal history during building through the analysis and estimated the effect of the building condition on the As-built microstructure. Then, we clarified the influence of the process parameter on the As-built microstructure from the comparison of the experimental and analytical results.<br/> <br/>The prior-β grain size, which is dominant in the As-built microstructure, largely depends on the spacing of the laser scan paths. In addition, it was indicated that the proportion of α’ martensite was related to the thermal history during building.