Abstract
Additive manufacturing has many process variables and requires additive process optimization. Line energy and scan speed are the main process variables. The objective of this work aims to investigate the effect of changes in line energy and scan speed among the process variables on the mechanical and fatigue properties of the Ti6Al4V specimens fabricated by electron beam additive manufacturing method. The size of the pore inside the specimen was 40~60 μm with the exception of the condition of 0.2 kJ/m, and the specimen with poor fusion of more than 100 μm and gas pore was found to have lower room temperature tensile and fatigue properties compared to the optimal process conditions. As line energy increased, strain hardening occurred, and yield strength and tensile strength increased. The EL:0.3 kJ/m and 800 mm/s condition is a process condition that shows no defects such as unmelted powder and poor fusion, and it represents the best fatigue strength of 400 MPa. The fatigue strength of the specimen performed with hot isostatic pressing after additive manufacturing was measured at 550 MPa, an increase of 150 MPa, which resulted in high fatigue strength enhancement. The crack initiation site and propagation behavior were analyzed by observing the fatigue fracture section of the specimen according to the line energy.
Highlights
Additive manufacturing technology using powder has been largely developed and has been used in various fields, including polymers, ceramics, stainless steel, Ti alloy, Co-Cr alloy, and Ni alloys for aircraft in recent years [1,2,3,4,5,6,7,8]
The powder bed fusion (PBF) method that builds specimens by radiating heat after spraying the powder onto a powder bed is a typical way of the selective laser melting (SLM) and electron beam melting (EBM) methods [9,10,11,12,13,14], and this study used the EBM method to conduct the additive manufacturing process
In the AM fabrication process with a scan speed of 800 mm/s, the process conditions of 0.3–0.35 kJ/m were shown to be suitable for the additive manufacturing by melting Ti6Al4V powder compared to the process conditions of 0.2–0.25 kJ/m
Summary
Additive manufacturing (hereinafter AM) technology using powder has been largely developed and has been used in various fields, including polymers, ceramics, stainless steel, Ti alloy, Co-Cr alloy, and Ni alloys for aircraft in recent years [1,2,3,4,5,6,7,8]. Polymer materials can be fabricated to variable shape but have low strength compared with additive manufacturing using metal powder. In particular Ti6Al4V alloys, represent excellent properties such as ductility, strength, heat resistance, and corrosion resistance, and are excellent materials that are widely accepted in the fields of energy and biomaterials. An additive manufacturing process changes the mechanical and physical properties of fabricated materials according to different process variables. The powder bed fusion (PBF) method that builds specimens by radiating heat after spraying the powder onto a powder bed is a typical way of the selective laser melting (SLM) and electron beam melting (EBM) methods [9,10,11,12,13,14], and this study used the EBM method to conduct the additive manufacturing process
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