Page 35 - MSAM-3-2

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

thereby weakening the bonding strength of the Ti6Al4V/ of approximately 417 MPa. These results underscore
AlSi12 multi-material parts, which exhibited a tensile the effectiveness of Ti/Al-graded multi-material parts
strength of approximately 110 MPa. In a separate study, in alleviating issues such as cracking deformation and
Wu et al. utilized LPBF to fabricate Ti6Al4V/AlSi10Mg inferior performance caused by differences in properties
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multi-material parts, achieving a good metallurgical between Ti and Al at the interface.
bonding with a transition zone width of only 0.1 mm. The In this study, a graded joining method was employed,
in situ generated nanoparticles Ti Si during interfacial which added a composition-graded layer (25 wt.% Ti6Al4V
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reactions improved interfacial bonding, resulting in a + 75 wt.% AlMgScZr) to avoid excessive formation of
tensile strength of 264.8 MPa. However, a large lattice brittle IMCs and consequent property mismatch. This
distortion at the interface was observed, attributed to the method facilitated a gradient transformation from the
absence of heat treatment.
interface composition while ensuring good metallurgical
It has been reported that the direct joining strategy for bonding. The Ti6Al4V/AlMgScZr-graded multi-material
fabricating multi-material parts consisting of Ti alloy and parts were fabricated using LPBF technology. Detailed
Al alloys often leads to the formation of cracks. These cracks investigations were conducted on the relationships between
primarily arise from the abrupt change in the composition process parameters, densification behavior, microstructure
at the interface and the mismatches in properties between evolution, and mechanical properties. In addition, the
the two materials. Therefore, Liu et al. fabricated mechanisms underlying the IMC generation and crack
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Ti6Al4V/AlSi10Mg-graded multi-material parts using formation were elucidated, providing a fundamental
LDED. In their study, the composition gradually changed understanding of LPBF-processed Ti6Al4V/AlMgScZr-
from 100 vol.% Ti6Al4V to 100 vol.% AlSi10Mg, effectively graded multi-material parts.
mitigating interface properties mismatch at the interface.
Their results indicated a gradual variation in microstructure 2. Materials and methods
and phase constitution with the increasing proportion of 2.1. Materials
AlSi10Mg, leading to the formation of a graded reaction
transition layer approximately 2-mm thick along the In this study, Ti6Al4V/AlMgScZr-graded multi-material
building direction. This transition layer comprised α-Ti → parts were fabricated using gas-atomized Ti-6Al-4V
AlTi → Al Ti + Ti Si + Al Ti → Al Ti + Ti Si + Al Ti + powders (TLS Technology Co. LTD, Germany) and
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Al → Al Ti + Al. Despite the increased thickness of IMCs, Al-4.2Mg-0.6Sc-0.2Zr powders (Heraeus Materials
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the systematic gradient variation of these compounds Technology, Taiwan, China) with particle sizes distribution
also resulted in a gradual change in microhardness along of 20 – 67 μm (Figure 1A) and 22 – 67 μm (Figure 1B),
the building direction, culminating in a tensile strength respectively, were used. Ti6Al4V powder and AlMgScZr
A B

C D E

Figure 1. The raw materials for laser powder bed fusion-processed Ti6Al4V/AlMgScZr-graded multi-material parts. (A) The particle size distribution and
morphology of Ti6Al4V powders. (B) The particle size distribution and morphology of AlMgScZr powders. (C) The morphology of graded powder, (D)
the Ti element distribution of graded powder. (E) The Al element distribution of graded powder. Scale bars: (A and B) 50 μm, magnification ×500; (C-E)
100 μm, magnification ×1000.

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