Functionally graded Ti6Al4V-Mo alloy manufactured with DED-CLAD® process

Abstract

This paper presents the results of functionally graded Ti6Al4V-Mo alloy manufactured with directed energy deposition called CLAD ® (Construction Laser Additive Direct) process. Single track width sample with five gradients of composition, from 0 to 100 wt.% Mo, was manufactured using a coaxial nozzle. Both Ti6Al4V and Mo ratios were modified with a 25 wt.% increase or decrease in the chemical composition of each gradient. A two-powder feeder was used to input the correct ratio of each powder, so as to obtain the desired chemical composition. XRD analysis allowed to define the phases present in each deposition, as well as the lattice parameter. SEM observations showed microstructural evolution from 25 wt% Mo on, namely where the ␤-phase becomes dominant. Moreover, dendrites appear from 50 wt.% Mo on. Microhardness analysis revealed variation along the deposition depending on the chemical composition. The homogeneity of the powder mixture under laser beam was highlighted thanks to tomography on the manufactured samples, which validates the processability of functionally graded material (FGM) by CLAD ® process.

On the Use of Functionally Graded Materials to Differentiate the Effects of Surface Severe Plastic Deformation, Roughness and Chemical Composition on Cell Proliferation

“…The microstructure features of the different graded materials in their as-deposited states has been detailed previously [34,35]. The main features are just recalled in Figure 1b,c for the sake of clarity.…”

“…The powders and manufacturing data (power, speed, pitch, etc.) of the samples have been detailed in the works of Schneider et al [34,35]. The FGM walls were cut into 1.5 mm thick slices.…”

“…The evolution of the microstructure for the Ti-Nb and TA64-Mo walls shared a number of aspects and the features shown in Figure 1b,c for TA64-Mo pertain for the other FGM sample. Because of the fast cooling rate [34,35], the initial layers of Ti or Ti6Al4V were characterized respectively by a Widmanstätten or a martensitic α' microstructure, issued from the high temperature parent phase nucleated from the melt (Figure 1c). With the addition of Nb or Mo, the microstructure became beta equiaxed with a decreasing grain size as the alloying element amount increased (Figure 1b).…”

“…To this end, FGMs have been made based on the Ti-Nb and Ti6Al4V-Mo constituents and then treated by SMAT. The FGMs compositions range from 100% Ti to 100% Nb as well as 100% Ti6Al4V to 100% Mo and were manufactured with a DED technique called CLAD® [34,35]. The FGMs were investigated in their polished (P), SMATed (S) and SMATed + polished (S+P) conditions then human mesenchymal stem cells were deposited and counted as function of time from three up to 21 days.…”

Multiscale study of different types of interface of a buffer material in powder-based directed energy deposition: Example of Ti6Al4V/Ti6Al4V - Mo/Mo - Inconel 718

“…T good miscibility between the two materials), and sharp interfaces which form intermetallic phases, that have bad mechanical properties and tend to separate easily. For example Schneider-Maunoury et al [6] showed that there is a good metallurgical bonding between different gradients in a Ti6Al4V-Mo alloy FGM made with CLAD®. Moreover Onuike and Bandyopadhyay [7] studied the interface between Inconel 718 and Ti6Al4V using additive manufacturing and showed that to construct a FGM with these two materials, a buffer material is needed due to numerous defects (delamination, intermetallic phases, cracking) when the two materials are directly in contact.…”