This PDF file contains the front matter associated with SPIE Proceedings Volume 11183, including the Title Page, Copyright information, Table of Contents, Introduction, and Author and Conference Committee lists

Ultraviolet (UV) solid-state laser has become an effective tool of processing hard and brittle materials due to its short wavelength, small spot and better beam quality. In this paper, experiment on the microgroove of hard and brittle sapphire wafers was carried out using a solid-state nanosecond laser with a wavelength of 266 nm. Samples were detected by scanning electron microscope(SEM) and optical microscope. The microgrooves on sapphire wafers were fabricated with different laser parameters through linear scanning experiments. The effects of laser energy, number of laser scans, and scanning speed on groove width and depth were investigated.

Transparent brittle materials such as glass and sapphire are widely concerned and applied in consumer electronics, optoelectronic devices, etc. due to their excellent physical and chemical stability and high transparency. Laser induced backside wet/dry etching (LIBWE or LIBDE) refers to the technique of applying absorber (liquid or solid layers) on the rear surface of workpiece and then focusing the beam on the liquid-solid interface for machining. High aspect ratio microgrooves and various microstructure are fabricated on glass and sapphire substrates quickly and accurately, which has been proved to be an effective and flexible way to process all kinds of transparent brittle materials with high-precision and highquality. The removal mechanism and model are revealed by considering the physical phenomenon like plasma, cavitation, micro-jet, etc. Additionally, applications of these techniques in micromachining, patterning, microfluidic, and microcircuit are introduced in detail.

Hierarchically porous structured materials with multifunctional properties and higher order complexities are highly desirable for many applications such as separation and energy storage. Here we describe the generation of hierarchically porous organic and inorganic structures coupling block copolymer self-assembly with spatially- and temporally controlled laser irradiation. A simple and rapid laser irradiation of block copolymer-directed hybrid films with a continuous wave laser in the sub-millisecond timescales enabled synthesis of 3D mesoporous polymer structures and shapes. Backfilling the polymer template with amorphous silicon followed by pulsed laser annealing enabled transient melt transformation of amorphous precursors into 3D mesoporous crystalline silicon nanostructures. Mechanistic studies on laser-induced crystalline silicon nanostructure formation during the nanosecond silicon melt-crystallization process and polymer template stability at temperatures above 1250 degrees Celsius are highlighted.

Nowadays, lasers, as innovation tools, provide extraordinary opportunities in a wide range of material processing and manufacturing applications. Here, we present using an ultra-short laser to fabricate a flute in a university’s lab on a syringe needle. By finely controlling the laser power and drilling time, holes can be drilled at one side but not penetrate the whole needle. With a set of holes arranged in a straight line, the needle acts as a “flute” when the gas flows into it. A microphone measures its acoustic frequency. Different tones were observed by changing the resonance length of the needle. Our work demonstrates the fabrication and testing of miniature flute on a syringe needle.

One of the challenges in the automotive industry is to reduce the carbon emission of manufactured vehicles. This can be done by incorporating light-weight metallic alloys, such as aluminum alloys and magnesium alloys, with more generic automotive modulus often made of high strength steel in order to reduce the total mass of a vehicle. To improve the load bearing capacity of dissimilar joints, optimization of the intermetallic layer thickness and the suppression of interfacial defects are key elements. In this study, a brief review is performed on the recent research progresses on laser joining of aluminum alloy to steel, in terms of different welding technologies including laser keyhole welding and laser welding brazing. Some suggestions were also put forward in the conclusions.

Laser cutting is considered as an effective tool to process the carbon fiber reinforced plastics (CFRP), but it is still a problem how to eliminate the heat affected zone (HAZ). In this paper, numerical simulation of laser cutting CFRP with different resin contents is carried out in order to investigate the formation mechanism and the effect of resin content on the HAZ. The energy distribution characteristics and heat transmission mechanism during laser cutting CFRP was studied through a finite element method. A model of laser-cutting of single-layer CFRP with different resin content was established by COMSOL multi-physics software to analyze the temperature field. The simulation results show that the absorbed laser energy is mainly transmitted along the direction of the carbon fiber laying. The maximum temperature of the surface carbon fiber in CFRP increases as the resin content increases. However, the width of HZA was decreases as the resin content increasing.

With the lightening tendency in the automobile and aircraft industry, the aluminium (Al) alloy and the carbon fiber reinforced thermal polymer (CFRTP) has been widely used. The CFRTP component always needs to be joined with Al alloy to form a CFRTP/Al alloy composite structure. Due to the large differences in the physicochemical properties of CFRTP and Al alloy materials, it is difficult to join with each other. Laser stir welding technology was applied to join CFRTP and Al alloy dissimilar materials in this research. In order to improve the CFRTP/Al alloy joining strength, a surface pre-treating method (laser micro-engraving) was proposed in this paper. Three micro-scale structures were designed and prepared on 7075 Al alloy by surface laser micro-treatment, which are linear grooves, mesh grooves and circular grooves. The morphology and dimensions (width and depth) of the microstructure on the strength of CFRTP / Al alloy joints were studied. The interface morphology and the fracture morphology of the joint were observed by the laser confocal microscopy and the scanning electron microscopy (SEM). Furthermore, the joining mechanism and failure mechanism of the CFRTP/Al alloy joint were explored. The results indicated that the microscale structures play an important role in improving the mechanical properties of Al alloy and CFRTP joins under different laser micro-engraving.

AlCrFeMnNi high-entropy alloy was prepared by laser additive manufacturing with gas-atomized pre-alloy powders. The phase, microstructure and microhardness of HEA have been investigated. The HEAs without electric field controlled and under controlled were composed of single BCC phase. Under the controlling of electric field, the pores presented the phenomenon of reducing. Due to the reducing of pores, the HEA under electric field controlled became harder and exhibited high microhardness of about 529.9 HV_0.2, which was 6.49% higher than the HEA without controlled.

In order to realize the laser precision machining of ceramics, the influence of some basic machining parameters (power, scanning speed, scan path spacing, and incidence angle) on the machining effect was studied. The experimental results show that the selection of reasonable processing parameters can obtain better processing quality and processing efficiency. The material removal rate firstly increases, and then decreases with the increment of the incident angle, which indicates that the incident angle has a great influence on the utilization of laser energy. In addition, the machined surface roughness is better after machining at high scanning speed and low power.

The anti-icing surface of stainless steel with hydrophobic properties can be used in many fields: aircraft, power grid systems and wind power plants, etc. In this paper, the surface of stainless steel with micro-nanostructure morphologies was prepared by femtosecond laser and the surface chemical modification method was used to obtain hydrophobicity. We systematically studied the effect of low temperature environment on the anti-icing performance of micro-nanostructured surface. The results show that these structured surfaces can effectively delay the formation of ice. The formation of this phenomenon is related to its surface wetting properties and micro-nanostructure.

We present the results of high-ordered periodic surface structure formation by femtosecond laser pulses (λ = 1026 nm, τ = 232 fs) using an astigmatic Gaussian beam with a diameter of ≈100 μm on the surface of metal films (thickness of 15 nm and 150 nm) of Hf sputtered on the glass substrate. Continuous and uniform structures with a period of ≈700 nm are formed at a scanning speed up to 2000 μm/s on the film with a thickness of 15 nm. In addition, the formation of ablative periodic substructures with a period of about 160 nm oriented perpendicularly to the main ones was observed on the oxide protrusions. In the case of 150 nm thick film, defects, cracks and phase shifts accompanied a uniform structure with a period of ≈940 nm formed at a speed up to 500 μm/s.

This paper proposed a new high-surface-quality and high-precision small hole processing technique by using laser and electrochemical hybrid machining (LECM) based on internal total reflection (ITR). During LECM via ITR the laser beam could be transferred to the large depth with a small attenuation machining area as the tube electrode feeds into the inner workpiece. The mechanisms of LECM via ITR has been clarified. The ITR through the tube electrode is also studied, in mathematical and simulation manner. Additionally, with the developed experimental setup, the feasibility of LECM via ITR has been proved. Experimental results demonstrated that the side gap could be decreased by laser assistance in LECM, and the side gap has been decreased by 25%.

Water-guided laser processing technology can be used for precision machining of refractory materials such as superalloy and composite materials. Compared with traditional short-pulse laser processing, it has the advantages of less thermal damage, smaller taper and greater depth, cleaner surface and so on. However, the existing technologies have two key problems of low laser coupling power and poor process reliability, which seriously affect laser processing efficiency and workpiece processing quality. Based on this situation, a water-gas shrinkage-guided high-power laser processing (WSLP) technology is proposed innovatively in this paper. Firstly, the laminar shrinkage mechanism is analyzed. secondly, the characteristics of water-gas contraction and total reflection conducting laser are investigated by simulation. The results show that water-gas compressibility effect can make water-jet compressed to within 0.1mm; and some systematic disturbance does not affect the laser coupling efficiency because of the total reflection effect at the water-gas interface, which verifies the stability and reliability of the system. In addition, water-gas shrinkage coupling experiment and total reflection conducting laser experiment are completed. The experiment result shows that the laser coupling efficiency can reach up to 93%; The feasibility of the system processing is verified by the tests.

Selective laser melting (SLM) is one of the important additive manufacturing technologies which can produce high quality parts with complex geometry. The main objective of current study is to investigate laser welding of 2 mm thick AlSi10Mg parts fabricated by SLM, and to emphasis on the weld shape, microstructure, pore distribution and hardness of the welded joints. The results show that the cross section of the welds is multi-pass welding appearance, and the cross-sectional area of the welded joints increases from 1.58 mm² to 3.66 mm² with increasing heat input from 51 J/mm to 135 J/mm. The increased heat input causes the grain size of the welds to increase from 1.1 μm to 2.5 μm. Circular pores are observed under different heat inputs, and the maximum pore diameter increases from 92.0 μm to 155.4 μm with the increase of heat input. The hardness of the weld zone is lower than that of the base metal, whereas the increase in heat input causes the average hardness to decrease from 86.7 HV to 77.8 HV. These preliminary results demonstrate that it is the feasible to joining SLM AlSi10Mg parts by using laser welding process.