Page 36 - MSAM-3-2

Materials Science in Additive Manufacturing LPBF of Ti-Al-graded multi-materials

powder were homogeneously mixed in a weight ratio of 25 building heights were used, as shown in Figure 2C. In
to 75 (Figure 1C-E). Mixing was performed using a V-10L addition, cylindrical samples with a length-to-diameter ratio
V-shaped mixer (Changsha Miqi instrument equipment of 1.5:1 were processed for compression testing. The parts
Co., LTD, China) under an argon atmosphere, with a produced using LPBF are presented in Figure 2D.
mixing time of 0.3 h and a mixing speed of 50 r/min.
2.3. Physical characterization of the samples
2.2. Graded multi-material parts LPBF process The LPBF processed samples were ground and polished
A self-developed LPBF-80 apparatus was used to fabricate following standard metallographic procedures, followed
the Ti6Al4V/AlMgScZr-graded multi-material parts. The by etching using Kroll reagent (1 mL HF, 2 mL HNO ,
3
apparatus consists of a 200 W fiber laser with a spot size of 47 mL H O, Sinopharm Chemical Reagent Co., Ltd.,
2
70 μm, an automatic powder spreading system, a process China) for 30 s. The density of the LPBF processed parts
control system, and a protective atmosphere system. The was measured according to Archimedes’ principle. The
schematic of graded multi-material parts for the LPBF crack area was observed using an optical microscope (OM)
process is illustrated in Figure 2A. Initially, Ti6Al4V powder (BX53M, OLYMPUS, Japan) and calculated using Image J
was spread onto a room-temperature Ti6Al4V substrate at software (National Institutes of Health, USA). The surface
oxygen concentration below 50 ppm, employing a flexible roughness of the graded layer was examined using a LEXT
rubber recoater blade to fabricate the Ti6Al4V layer. OLS5000 laser confocal scanning microscope (OLYMPUS,
Subsequently, the powder cylinder and recycled product Japan). The microstructure of the Ti6Al4V/AlMgScZr-
were cleaned, and the graded powder and AlMgScZr powder graded multi-material parts at the interface was observed
were added to two separate powder cylinders to process the using a scanning electron microscope (SEM) (LYRA3,
subsequent layers. The Ti6Al4V/AlMgScZr-graded multi- TESCAN, Czech Republic), and the XFlash 6130 EDS
material samples were fabricated using the parameters listed system (BRUKER, YYY) was used for characterizations
in Table 1, with both Ti6Al4V and AlMgScZr adopting their to identify the parts and element distributions around the
respective optimized laser process parameters. However, the interface. Phase constitution was measured using a D8
graded layer exhibited a high propensity to crack under the Advance X-ray diffractometer (XRD) (Germany) with Cu
same heat input as Ti6Al4V and AlMgScZr, which could be Kα radiation at 40 kV and 45 mA, in the 2θ range of 30° –
reduced by appropriately increasing the scanning speed of the 90° and a scan rate of 4°/min.
graded layer. An island scanning strategy with a rotation angle
of 37° between layer N and layer N+1 was applied to mitigate 2.4. Characterization of mechanical properties of
the effect of thermal stress (Figure 2B). For microstructure the samples
analysis of the interface, cubic samples with two different Microhardness tests were performed using a Micromet

A B

C

D

Figure 2. Schematic and experiments of LPBF-processed Ti6Al4V/AlMgScZr-graded multi-material parts. (A) Schematic of graded multi-material
parts LPBF process. (B) The chessboard scanning strategy applied in LPBF. (C) The graded multi-material block model. (D) The laser-processed parts.
Abbreviations: CAD: Computer aided design; LPBF: Laser powder bed fusion.

Volume 3 Issue 2 (2024) 4 doi: 10.36922/msam.3088