Influence of Island Scanning Strategy on Microstructures and Mechanical Properties of Direct Laser-Deposited Ti–6Al–4V Structures

Abstract

To investigate the influence of island scanning on the microstructures and mechanical properties of direct laser-deposited Ti-6Al-4V structures, two samples are prepared using island scanning and orthogonal successive scanning, respectively. The microstructures, relative density, and mechanical properties of the samples prepared using these two scanning strategies are compared. Each sample exhibits columnar β-grain morphology and basket-weave microstructure characterization. The grains of the sample prepared using island scanning are significantly finer than that prepared by orthogonal successive scanning due to faster cooling during deposition. However, the relative density of the sample prepared using island scanning was slightly smaller due to the concentration of lack-of-fusion pores at the overlap zone of the island. Tensile testing at room temperature indicates that the ultimate tensile strength and yield strength of the sample prepared using island scanning is enhanced due to finer grains, while the ductility of the sample is weakened due to defects.

Microstructure of a Ti–50 wt% Ta alloy produced via laser powder bed fusion

“…They found similar cellular morphology, but α″ phase was not observed in the cellular boundaries. The phase difference might be caused by the different LPBFed equipment and scanning strategies [41]. Besides, this paper investigated the detailed microstructure such as cellular/dendritic features and phase transformation and a new method for controlling microstructures with different phase distributions in a fine cellular structure via laser powder bed fusion.…”

Design of high strength titanium alloy through finding a critical composition with ultra-fine α phase

“…Although there is no evidence in the microstructure image [ figure 6] of this experiment that the alloy has smaller β grain size after solution treatment in the two-phase region (due to the smaller field of view of TEM image). However, previous studies have shown that the primary α phase at the β boundary can effectively inhibit the growth of β phase and produce smaller β grains [29]. The small grain size can increase the ductility of the alloy, because it can make the cooperative deformation between grains easier and enhance the crack growth resistance.…”

Influence of scanning strategies on laser-cladded AISI 420 steel

“…It is widely accepted that the laser scanning strategy is one of the main processing parameters influencing the thermal distribution and substrate deformation [4][5][6][7][8][9][10][11][12][13][14]. However, there are still a few consensuses on the deformation behaviour and performance of the laser-manufactured parts using different scanning strategies as follows: (1) Effects of subarea strategy on deformation.…”

“…( 2) Effects of scanning strategies on mechanical property. Wang et al [9] found that the tensile strength of the as-deposited Ti6Al4V alloy was enhanced by using subarea raster scanning strategy (SRSS) in comparison to a continuous raster scanning strategy (CRSS), and it was believed that the SRSS could lead to a finer grain size, caused by the higher cooling rate with shorter scanning length. In contrast, Lu et al [6] demonstrated that there was no direct correlation between the scanning strategy and the strength of SLMed Inconel-718 alloy.…”