Insights into fabrication mechanism of pure copper thin wall components by selective infrared laser melting

Abstract

Purpose This study aims to obtain the mechanistic insights for the fabrication of pure copper thin wall components by selective infrared (IR) laser melting (SLM) and correlated with microstructure development, microhardness, surface morphology and phase analysis. Experimental processes for single track and selection of substrate materials have been studied using a combination of different laser powers and scanning speeds. Design/methodology/approach SLM of pure copper was performed on a YONGNIAN Laser YLMS-120 SLM machine using an Nd: YAG fiber laser operating at 1,060 nm in the NIR region. Single-track experiments and processing parameters are investigated through different combinations of laser power and scanning speed. The microstructure of the fabricated pure copper samples by SLM technique was analyzed by means of X-ray diffraction, scanning electron microscope equipped with energy disperse spectrometer, optical microscope (OM) and micro-hardness tester. Findings Steel-based substrates were found suitable for pure copper manufacturing due to sufficient heat accumulation. The width of a single track was determined by liner energy density, showing discontinuities and irregular morphologies at low laser powers and high scanning speeds. As a result of instability of the molten pool induced by Marangoni convection, cracks and cavities were observed to appear along grain boundaries in the microstructure. The top surface morphology of SLM-processed component showed a streamflow structure and irregular shapes. However, the powder particles attached to side surface, which manifest copper powders, are even more sensitive to melt pool of contour track. The crystal phase characteristics of copper components indicated increasing crystallite size of a-Cu, and the decreasing intensity of diffraction peak was attributed to the presence of defects during SLM. The maximum relative density and microhardness were 82 per cent and 61.48 HV0.2, respectively. The minimum thickness of a pure copper thin wall component was 0.2 mm. Originality/value This paper demonstrated the forming mechanism and explored feasibility of pure copper thin wall parts by SLM technology in the NIR region. The surface morphology, microstructure and crystal structure were preliminary studied with laser processing parameters.

A Review on Additive Manufacturing of Pure Copper

“…In the study of Ashwath et al [48], they obtained a sample with the highest density of 83.6%, and the tensile strength obtained after the tensile test was 115.8 MPa. Compared with the study of Guan et al [40], the tensile strength is higher. This is because the influence of internal stress is greatly reduced due to the heat preservation process in the powder sintering process, while the SLM technology is due to It is a rapid cooling process, so the internal stress existing in the low-density parts will reduce the mechanical properties of the sample.…”

“…The pure copper powder has a reflectivity of 71-72% to this wavelength range laser [27]. In the early years of commercial SLM equipment, the maximum power was generally less than 200 W [10], so the relatively high density of formed parts was rarely produced in the study of pure copper at that time [40]. In addition, it can be seen from Figure 10 that when the energy density is concentrated in the region of 250-750 J/mm 3 (the green region in Figure 10), combined with high power, parts with relatively high density could be obtained.…”

“…After testing, it was found that the tensile strength of the parts was 149 MPa. Guan et al [40] produced parts with SLM additive manufacturing technology with a relative density of 82% and a microhardness of 61.48 HV. This shows that the mechanical properties of the parts are seriously affected by the relative density.…”

“…Figure10. The relationship between laser power and relative density of pure copper part manufactured via SLM additive manufacturing[1,2,5,7,9,10,27,37,[39][40][41][42]44].…”

Forming feasibility and interface microstructure of Al/Cu bimetallic structure fabricated by laser powder bed fusion

“…The L-PBF experiments were performed on a self-developed machine which has been addressed (Guan et al , 2019). The optimized processing parameters were also reported (Guan et al , 2019; Guan et al , 2020).…”