Preparation Of TC11 Alloy 3D Printing Powder And Mechanical Properties Of Printed Parts

TC11(Ti-6.5Al-3.5Mo-1.5Zr-0.3Si)alloy is widely used in key structural components such as aerospace engine blades due to its high specific strength,good high temperature mechanical properties and low density.At present,the alloy is mostly used for forging to achieve one-time near-net forming of such complex parts.However,3D printing,as a new forming and manufacturing technology,has obvious advantages in one-time near-net forming of complex structural parts and additive manufacturing repair of complex structural parts.Therefore,it is of great theoretical value and practical significance to prepare special powder for 3D printing of TC11 alloy and study its mechanical properties.In this study,TC11 alloy was selected as the research object,and the optimal process parameters for preparing alloy powder by electrode induction melting gas atomization(EIGA)were determined.The 3D printing of the alloy in different directions was realized by laser selective melting(SLM)method.The hot isostatic pressing heat treatment process test was carried out on the printed parts,and the tensile behavior at room temperature and low cycle fatigue behavior at high temperature under the above different states of the alloy were studied.The main results are as follows:(1)The optimal process parameters of TC11 alloy powder prepared by EIGA method are atomization pressure 6MPa and melting power 30 k W.The powder prepared by this process has small particle size,good sphericity and surface quality,low hollow powder content,no burning loss of elements,and low oxygen increment,which meets the requirements of SLM for powder properties.The powder surface is cellular structure and the cross section is acicular martensite.(2)The microstructure of the deposited sample prepared by SLM method is acicular α’martensite with closely packed hexagonal structure,and the grains grow upward along the deposition direction,with obvious deposition layer and anisotropy,and there is an unfused defect in the tensile fracture.The microstructure of the hot isostatic pressed sample is α + β net basket structure,the two-phase orientation confusion increases,the orientation relationship weakens,the anisotropy is weakened,and the deposited layer and the unfused defects in the fracture morphology disappear.Compared with the deposited state,the plasticity is obviously improved.The longitudinal printing samples of the two states show low strength and high plasticity compared with the transverse printing samples.(3)In the high temperature and low cycle fatigue test of the hot isostatic pressed sample,the cyclic stress response behavior of the longitudinally printed sample is cyclically stable in the range of 0.5%～1.0% external strain amplitude;the transversely printed sample shows cyclic stability in the range of 0.5%～0.8% external strain amplitude,and cyclic softening occurs at 1.0%strain amplitude.Under 0.5%～1.0% additional strain amplitude,the cyclic deformation resistance of the transverse printed sample is higher than that of the longitudinally printed sample,and the fatigue life is lower than that of the longitudinally printed sample.The fatigue cracks of the samples with different printing directions germinate on the surface of the specimen and propagate in a transgranular manner.