Robust interface and excellent as-built mechanical properties of Ti–6Al–4V fabricated through laser-aided additive manufacturing with powder and wire

The feasibility of manufacturing Ti-6Al-4V samples through a combination of laser-aided additive manufacturing with powder(LAAM_(p))and wire(LAAM_(w))was explored.A process study was first conducted to successfully circumvent defects in Ti-6Al-4V deposits for LAAM_(p) and LAAM_(w),respectively.With the optimized process parameters,robust interfaces were achieved between powder/wire deposits and the forged substrate,as well as between powder and wire deposits.Microstructure characterization results revealed the epitaxial prior β grains in the deposited Ti-6Al-4V,wherein the powder deposit was dominated by a finerα′microstructure and the wire deposit was characterized by lamellar α phases.The mechanisms of microstructure formation and correlation with mechanical behavior were analyzed and discussed.The mechanical properties of the interfacial samples can meet the requirements of the relevant Aerospace Material Specifications(AMS 6932)even without post heat treatment.No fracture occurred within the interfacial area,further suggesting the robust interface.The findings of this study highlighted the feasibility of combining LAAM_(p) and LAAM_(w) in the direct manufacturing of Ti-6Al-4V parts in accordance with the required dimensional resolution and deposition rate,together with sound strength and ductility balance in the as-built condition.

Additive manufacturing of high-entropy alloys by thermophysical calculations and in situ alloying

Electron beam melting(EBM)is a promising technology to manufacture various alloys with outstanding properties;however,the number of available alloys is limited.We propose in situ alloying to accelerate the development of advanced and novel alloys,based on thermophysical calculations and CALPHAD approach,during the EBM process.We demonstrate our concept through the design and fabrication of high entropy alloys(HEAs).Three CoCrFeNiMn-xTi(x=0.18,0.50,2.00,in molar%)HEAs are manufactured.EBM-built HEAs achieve a homogeneous distribution of elements while forming multiphase alloys resulted from the hot powder bed.The topological structures formed by secondary phases contribute to an increase in the hardness of EBM-built HEAs up to 900 HV1.Considering alloy design,a systematic analysis on Co Cr Fe Ni Mn-0.18 Ti HEA elucidates the microstructural evolution in detail.These findings provide a deep understanding of in situ alloying and pave the way to develop new alloys specific to the EBM process.