Abstract
For analysis of engineering structural materials to withstand harsh environmental conditions, accurate knowledge of properties such as flow stress and failure over conditions of high strain rate and temperature plays an essential role. Such properties of additively manufactured Ti6Al4V(ELI) are not adequately studied. This paper documents an investigation of the high strain rate and temperature properties of different forms of heat-treated Ti6Al4V(ELI) samples produced by the direct metal laser sintering (DMLS). The microstructure and texture of the heat-treated samples were analysed using a scanning electron microscope (SEM) equipped with an electron backscatter diffraction detector for electron backscatter diffraction (EBSD) analysis. The split Hopkinson pressure bar (SHPB) equipment was used to carry out tests at strain rates of 750, 1500 and 2450 s−1, and temperatures of 25, 200 and 500 °C. The heat-treated samples of DMLS Ti6Al4V(ELI) alloys tested here were found to be sensitive to strain rate and temperature. At most strain rates and temperatures, the samples with finer microstructure exhibited higher dynamic strength and lower strain, while the dynamic strength and strain were lower and higher, respectively, for samples with coarse microstructure. The cut surfaces of the samples tested were characterised by a network of well-formed adiabatic shear bands (ASBs) with cracks propagating along them. The thickness of these ASBs varied with the strain rate, temperature, and various alloy forms.
Highlights
Direct metal laser sintering (DMLS) is in the additive manufacturing (AM) category of powder bed fusion (PDF) and produces solid parts from 3D CAD models in a layer-by-layer manner by melting metal powders with a focused high energy laser beam
Samples C were heat treated at 800 ◦C followed by furnace cooling (FC)
The three different microstructures of Ti6Al4V(ELI) produced by DMLS technology followed by heat treatment and their corresponding properties at high strain rate and temperature have been presented and discussed in this paper, with the following conclusions deduced:
Summary
Direct metal laser sintering (DMLS) is in the additive manufacturing (AM) category of powder bed fusion (PDF) and produces solid parts from 3D CAD models in a layer-by-layer manner by melting metal powders with a focused high energy laser beam. This technology was developed by Electron Optical System (EOS) GmbH of Munich, Germany and has been available commercially since 1995 [1]. The metals and alloys produced by this technology were limited, more materials options are currently being produced by the DMLS process These include steel, stainless-steel, tool steel, aluminium, bronze, cobalt-chrome, and titanium-based alloys [2]. This is mainly due to its range of applications in the aerospace and the biomedical industries, which is based on by its array of desirable properties, such as good fracture toughness, high specific strength, and biocompatibility [3,4,5]
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