The Laser Rapid Forming Technology With Low Cost Hydrogenation Dehydrogenization Titanium Alloy Powders

Laser rapid forming of titanium and titanium alloys was a promising manufacturing technology because it had several advantages, such as low cost, short lead times and excellent properties. In order to reduce the cost more and accelerate the application in the civil area, the laser rapid forming technology with low cost hydrogenation dehydrogenization ( HDH ) titanium alloy powders had been investigated, and the following results were obtained:1 Disclosed the formation mechanisms and influencing factors of the defects by studying the powder's characteristic and processing parameters:(1) The porosities were originated by entrapment of argon gas from shrouding environment. Increasing the loose density of the powders can decrease the gas porosity rate when the appearance and the particle size range of the powders were fixed.(2) The mismatching of the processing parameters was the main reason leading to the ill bonding. A dense sample with ideal quality was obtained by the optimized processing parameters, including the laser power, scanning velocity, overlap and Z-increment â–³ Z.2 Disclosed the influence regularity of element Nd on the structure and mechanical property of laser rapid formed HDH TC4 alloy.(1) As the increasing of the content of element Nd, the macrostructure of laser rapid HDH TC4 changed from prior β columnar crystal to complete β equiaxed crystal, and the primary Widmanstaten a structure transformed to basket weave a structure. The coarse a laths increased gradually and tended to gather. At the same time, the volume fraction of a cluster on the grain boundary increased obviously.(2) As the content of element Nd increased, the strength of the HDH TC4 decreased a little, and the plasticity increased significantly at first and then decreased sharply. The mechanism of action is that the addition of element Nd in proper quantities can scavenge the oxygen in the titanium matrix while the formed Nd₂O₃ particles can dispersion strengthened the titanium matrix to coverthe loss of solution strength. The excessive content of Nd would lead to theoversized Nd2O3 particles and the coarse grain boundary a phase, which led tofracture finally.3 By controlling the processing parameters, loose density of the powders and adding element Nd in proper quantities, low cost HDH titanium alloy powders can be used instead of expensive sphere powders in some conditions.