Investigation of the scanning strategy on the microstructure and tensile property of Ti6Al4V alloy fabricated by selective laser melting

The tensile properties and microstructure of Ti6Al4V titanium (TC4) alloy specimens fabricated by SLM under five scanning strategies were studied. They are the bidirectional scanning with a 67 degrees rotation (R-scan) strategy, bidirectional scanning along with x-axis (X-scan) strategy, bidirectional scanning along with y-axis (Y-scan) strategy, bidirectional scanning with a 90 degrees rotation in each layer (XY-scan) strategy, and the filled scanning strategy with homocentric squares (H-scan) strategy. Through the tensile experiments of specimens fabricated by different scanning strategies, it is found that the fabricated specimens by the XY-scan strategy show the best tensile properties. Compared with the R-scan strategy, the maximum tensile strength of the specimens prepared by the XY-scan strategy increased by 17.3%, and the maximum tensile strength reached 919.55 MPa. The tensile experiment of the fabricated specimens by the angle offset XY-scan strategy shows that the tensile property is the best when the offset angle is 45 degrees. Compared with the XY scanning strategy, the maximum tensile strength of the specimens prepared by the angle-shifted XY scanning strategy was increased by 46.1%, and the maximum tensile strength reached 1343.27 MPa. The fracture surfaces of the specimens are mainly composed of cleavage cracks and dimple cracks. The tensile properties are the worst when the fracture cracks are mainly cleavage cracks and the tensile properties are the best when the cracks are mainly dimple cracks. When the alpha '-phase direction of acicular martensite inside and outside the beta-phase of columnar crystal is parallel to the tensile direction, the tensile properties of specimens are improved. When the secondary alpha '-phase direction is parallel to the tensile direction, the tensile property is further improved.