Page 42 - MSAM-3-2

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

3000 mm/s, the average microhardness at the interface the compressive mechanical properties and the forming
decreased to 247 HV . This reduction in microhardness process or forming quality of the samples. Figure 10B
0.2
was attributed to cracks caused by insufficient powder illustrates the resultant ultimate compressive strengths
melting under conditions of excessive scanning speed and (σ ) and strains (δ) of the compressive samples. Analysis
bc
reduced heat input. of the compressive stress-strain curves reveals two distinct
stages. The first stage occurred within the deformation
To further investigate the mechanical properties of range of 22 – 30%, mainly involving the compression
Ti6Al4V/AlMgScZr-graded multi-material parts, each of AlMgScZr. The second stage occurred within the
sample underwent compressive testing. Figure 10A deformation range of 45 – 50% and primarily involved
depicts the compressive stress-strain curves for the LPBF- compression of the graded layer and Ti6Al4V. With an
processed Ti6Al4V/AlMgScZr-graded multi-material increase in scanning speed from 2400 – 2800 mm/s, the
parts at different scanning speeds. The compressive load compressive strength and strain increased from 1359 MPa
was applied vertically to the interface between Ti6Al4V and 46.7% to 1531 MPa and 49.8%, respectively. However,
and AlMgScZr. It is important to note that any cracks at a scanning speed of 3000 mm/s, the unmelted powders
or pores existing at the interface would close during the were observed at the interface, rendering the interface
compression process, which might not fully describe the susceptible to cracks and resulting in a decrease in
relationship between cracks and compression properties. compressive strength and strain to 1461 MPa and 47.9%,
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However, some quantitative relationships exist between respectively. The observed compressive performance is

A B

Figure 10. The compressive properties of laser powder bed fusion-processed Ti6Al4V/AlMgScZr-graded multi-material parts. (A) Compressive
stress-strain curves for Ti6Al4V/AlMgScZr-graded multi-material parts at different scanning speeds (Insets: The compression process of the sample at
2800 mm/s. Scale bars: 10 mm, magnification × 2.5;). (B) Comparison of the scanning speed on ultimate compressive strength (σ ) and failure strain (δ)
bc
of the compressive samples.
A B C

D E F

Figure 11. Scanning electron microscopic images showing the fracture morphologies of the laser powder bed fusion-processed Ti6Al4V/AlMgScZr-graded
multi-material parts at different scanning speeds. (A) 2600 mm/s on AlMgScZr side. (B) 2800 mm/s on AlMgScZr side. (C) 3000 mm/s on AlMgScZr side,
(D) 2800 mm/s on Ti6Al4V side. (E) Ti element distribution of (D). (F) Al element distribution of (D). Scale bars: (A-C) 20 μm, magnification ×3500;
(D-F) 100 μm, magnification ×400.

Volume 3 Issue 2 (2024) 10 doi: 10.36922/msam.3088