A mandrel-free hot-spinning was developed as a near-net-shape titanium alloy plate forming technique. In this work, a Ti-6Al-4V alloy conical product with a wall angle of 34 degrees and 170mm height was formed from a large size Ti-6Al-4V plate (890～920mm dia. × 30mm thick). The product was characterized metallurgically and mechanical properties were measured, and the shape of formed products was investigated. It was found that the mandrel-free hot-spinning is able to form a large size titanium alloy plate. Material properties including tensile strength and microstructure of the formed products satisfied the material specifications. Fatigue stress of the formed product was higher than that of the typical Ti-6Al-4V material. For a further improvement, a forming method using pre-formed material was proposed and which was successfully conducted with two types of preforms and found to be effective in the forming process.
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