Cyclic Aging Behavior Of TC4 Powder And The Influence On Properties Of Components Built By SLM

The Selective Laser Melting(SLM)technology could achieve high utilization of materials by recycling the forming materials(powder).While,multiple properties of the powder may change during the forming and recycling processes,and that could impair the products' quality of SLM.In this paper,the influence mechanism of the microstructure and multinomial mechanical properties of formed samples were analyzed in depth on the basis of multiple parameters evolution in the process of TC4 powder recycling.First of all,this paper studied many performance indexes of TC4 titanium alloy powder after recycling by means of SEM,laser particle size distribution instrument and multifunctional powder tester.The results show that the particles still kept morphology of sphere with the increasing recycle times;few satellite particles were observed after recycling14 times;the PSD experienced the course of concentration-dispersion-concentration;the powder tap density,apparent density decreased firstly then increased with the the increasing recycle times;the angle of repose,angle of collapse,angle of spatula decreased when recycling times increased;the recycled powder showed improved flowability.Secondly,by comparing the microstructure morphology,composition,martensite,porosity of the formed samples under different cycles,the influence of powder circulation on the microstructure of the SLM forming samples is studied.It was observed that the microstructure of the samples is not affected by the powder recycle times after multidirectional observing;the composition and martensite also showed no significant change;the porosity of the formed specimen increased firstly and then decreased with the increasing recycle times;the defects in the forming sample include spherical hole,flat type and irregular cavity type defects.Last but not least,the mechanical properties,such as hardness,tensile,fatigue and impact,were compared and studied under different cycles.The comparison results show that recycle times of TC4 powder had no effect on microhardness;tensile properties and powder recycle times show no significant correlation;fatigue properties and powder recycle times also have no significant correlation;Under different cycles,the impact toughness of SLM specimens is basically the same,and has no obvious relationship with the number of powder cycles.