Pulsed laser-assisted additive manufacturing of Ti-6Al-4V for in-situ grain refinement

Abstract

Metal additive manufacturing (AM) enables rapid customization of complex parts. However, it leads to forming of columnar grain structures which give the AM parts anisotropic properties. In this study, we propose a pulsed laser-assisted AM (PLAAM) technique for in-situ grain refinement of Ti-6Al-4V parts. A nanosecond pulsed laser was focused onto a melt pool to generate a favorable environment for the promotion of fine equiaxed grains. The PLAAM technique provided an average prior-β grain size of 549.6 μm, compared to that of 1297 μm provided by the conventional AM technique. Moreover, the maximum value of multiples of uniform distribution of the β phase decreased from 16 to 7.7 when using the PLAAM technique, which indicates a weakened crystallographic texture. These changes confirm that the proposed PLAAM technique promotes finer and more equiaxed prior-β grains. Furthermore, because the proposed technique is a non-contact technique, it can be applied to existing processes without adjusting tool paths.

Quantitative efficiency of optoacoustic ultrasonic treatment in SLM, DED, and LBW applications

“…Another method of influencing the crystallization process is the use of ultrasonic (US) technology, which is widely used in casting processes [18,19]. The novel experimental studies [20,21] have shown promising results in LBW and prospects in DED [22][23][24][25][26][27] and SLM [28]. Different materials such as Ti-6Al-4V [22], Inconel 625 [22], stainless steel 316L [23], Al-12Si [24], and Ti-TiB composites [25] were tested to investigate the effects of ultrasound treatment.…”

“…Different materials such as Ti-6Al-4V [22], Inconel 625 [22], stainless steel 316L [23], Al-12Si [24], and Ti-TiB composites [25] were tested to investigate the effects of ultrasound treatment. As described in [25][26][27]29], the ultrasound treatment results in reduced porosity, improves reinforcement, and leads to a refined grain structure.…”

“…There is no definitive description in literature regarding the exact influence of US on primary crystal structure. However, most researchers associate this phenomenon with the effect of acoustic cavitation of vapor-gas bubbles [20][21][22][23][24][25][26][27]. Bubble growth and collapse in molten metal alloys can occur rapidly (~30μs) [30], as revealed by studies using in situ synchrotron X-ray visualization [31].…”

“…Let us further consider the technologies of ultrasonic generation based on optoacoustic effects using laser radiation in a highly absorbing medium [26][27][28][49][50][51]. This method offers the benefit of producing localized ultrasonic vibrations while circumventing the constraints linked to a sonotrode.…”

F2 Laser-Induced Micro-Reticulated Structural Changes of Amorphous Carbon Thin Films

“…For example, the fabrication of three-dimensional microstructures is required for the enhancement of functionality and performance of microdevices. A laser additive manufacturing process based on thermal processing and non-thermal materials processing using ultrashort pulse lasers has been actively studied recently [1][2][3][4]. Besides these works, pulsed lasers that oscillate in the ultraviolet (UV) region, although the pulse width of the laser is tens of nanoseconds, are also capable of precise materials processing with no heat-affected zone of around the processing area [5][6][7].…”