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In this work, laser shock microhydroforming technology was further investigated. This technology employs liquid as the laser-induced shock wave transmission medium to microform a thin-walled LA103Z magnesium–lithium (Mg-Li) alloy foil with six bump features. A finite element model established by Hypermesh/LS-DYNA was used to illustrate the dynamic transmission of the liquid shock wave and the dynamic plastic deformation of the workpiece. The mechanism by which the liquid shock wave interacted with the closed liquid chamber to generate a homogenised shock wavefront was revealed. The dynamic loading form of the liquid shock wave and the characteristics of the microfeatures of the workpiece resulting from this dynamic loading form were also analysed mechanically. A comparison of the effects of liquid type and laser energy in this process showed that using castor oil as the liquid medium at threshold laser energy achieved the best plastic forming effect of the workpiece. Analysis of the thickness distribution of the workpiece revealed that the rupture was concentrated in the shear thinning region at the edge of the bump features caused by the transient large stress when the laser energy exceeded the threshold value.

Laser shock processing (LSP) was employed for the first time to fabricate nanoparticle reinforced metallic micro-parts for micro-electronic mechanical system. TiN/Al composite micro-part was punched by one laser operation to realize the synchronous sheet microblanking and particle implantation process and the reinforcement size effect on the performance of metallic micro-part was investigated. Results revealed that most nanoparticles are closely enfolded by the Al matrix with a strong mechanical bonding even though a few voids exist near clustered particles. The surface nanohardness of TiN/Al composite parts of 20 nm, 150 nm and 1 μm particle size has a considerable increment of 18.6, 86.8 and 95.7%, respectively, presenting favorably improved mechanical properties. These composite parts still shows high plasticity with the appearance of large rollover and the absence of fracture zone. Moreover, with increasing particle size, the injection depth of particle decreases, presenting a more notable gradient distribution. Although the surface roughness of TiN-reinforced micro-part increases with the reinforced particle size, the roughness of the flat region without particles decreases to be lower than raw material due to planishing effect of rubber pad loaded by LSP, which contributes to the improvement of surface quality of TiN/Al micro-part.

This study applies high rate forming technology to the manufacture of miniature parts and proposes a novel miniature parts bulk forming method, that is, laser shock micro-bulk forming (LSMBF). Through the numerical simulation and experimental research on 1100Al rod, the feasibility of manufacturing miniature parts using the LSMBF method is discussed. The similarities and differences of two simulation methods, namely, the smooth particle dynamics and finite element coupling (SPH-FE) and coupled Euler–Lagrangian (CEL) methods, were analyzed. Results show that the SPH-FE method is more consistent with the experiment and is more suitable for simulating the complex large deformation forming process of LSMBF than the CEL method. This study shows that the plastic deformation process of LSMBF is as follows. First, the upper end of the rod undergoes mushroom-shaped upsetting. Then, the bottom of the rod touches the micro die, and the upsetting phenomenon occurs. Finally, the micro-die is gradually filled. The plastic deformation of metal is related to the stress wave propagation and inertia effects. The main flow direction of the metal is axial, and the flow uniformity is fine. This study also shows that increasing the laser energy intensity is beneficial to improving the uniformity of the parts when impacting micro-die at high speed.

Pulsed current treatment was introduced into the laser impact microforming technology to improve the formability of laser impact forming. A pulsed current pretreatment–assisted laser impact microforming technology is proposed, and the formability and mechanism of such composite technology are discussed. In this study, the mechanical properties of H62 brass before and after pulse treatment were tested. The effect of pulsed current treatment on the formability of the material under high strain rate was studied by a laser impact free microbulging experiment. Moreover, the mechanism of pulsed current influence on the material’s formability was analyzed from the aspects of microstructure, texture evolution process, and grain size and morphology. Results showed that the elongation of the material was increased obviously, the flow stress during the tensile process was decreased significantly after pulsed current treatment, and the fracture form of the material gradually evolved from brittle fracture to ductile fracture. The forming height of samples under high strain rate improved greatly which may be due to the high-density pulsed current treatment that significantly alleviated the dislocation entanglement in the material. Owing to the weaker orange-peel effect which is induced by smaller recrystallized grains and lower maximum density of texture, the surface quality of formed parts after pulsed current treatment increased remarkably. In addition, the more uniform section thickness distribution of formed parts was observed, which may stem from obviously refined grains after pulsed current treatment improved the fluidity of the grains in a high–strain rate deformation process.

Laser shock hydraulic microforming (LSHM) is a new microforming that combines the advantages of laser shock microforming and impact hydroforming. LSHM uses monopulse laser to drive the rubber layer for squeezing liquid medium to form metal foils. The size effect and forming mechanism under this process will surely introduce new features, and they were explored in terms of maximum bulge height, surface topography, thickness distribution, microhardness, microstructure, and elastic recovery. When N=t/d (thickness/grain size)>1, the N value decreases, the maximum bulge height and thickness thinning increase, and the roughening of surface topography is not obvious. When N 4.3, this case accords with inverse Hall−Petch tendency because twin nucleation is dominant. When N 1 due to the increase in the scale of grain atoms. The increase in laser power density can appropriately reduce the elastic recovery ratio because of grain refinement.

Laser shock hydroforming is a novel microforming method that adopts laser energy as the driving force and liquid as the medium to transmit pressure. The method combines the advantages of laser shock forming and micro hydroforming. Previous research has demonstrated that this method can deform thin sheets into complex shapes at high strain rates. We know that the formability of materials is improved at high strain rates, but experimental analysis on this method alone cannot examine the deformation process. Therefore, this study first conducted free- and die-forming experiments of laser shock hydroforming to characterise the features of the deformation process and understand the factors that may contribute formability enhancement. Experimental results were discussed to uncover the formability of thin sheets under different conditions, including the laser energy and the effect of the die. Then, a numerical model was established considering fluid–solid interaction. The deformation process, sheet velocity, contact stress and strain rate were investigated through numerical means, and these indicators explain the mechanism of formability improvement in this method. Furthermore, the numerical results indicate a positive phenomenon—pressure equalisation—which might be due to the reflection of pressure off the rigid side wall of the liquid chamber.

In order to overcome the poor plasticity of amorphous alloy at room temperature, this paper uses soft film as a micro punch to punch out the gear hole on the amorphous alloy with a thickness of 30 μm under laser loading. This paper mainly studies the fracture morphology and fracture mode of the workpiece; the process window of laser energy and the thickness of soft punch; the mechanical properties and surface quality of the workpiece. The fracture surface of the workpiece is mainly composed of smooth zone and veined zone. There are two modes of brittle fracture and plastic fracture, and from the addendum to the dedendum of gear, the material gradually transitions from brittle fracture to plastic fracture. When the laser energy and the soft punch thickness are 1520 mJ and 200 μm respectively, the workpiece can achieve a balanced forming quality. With the laser energy increases, the softening effect caused by adiabatic temperature rise and free volume exceeds the hardening effect caused by compressive stress, resulting in nanohardness increasing first and then decreasing. And the change trend of the surface roughness is the same.

In this study, a novel micro-forming process called laser shock micro hydraulic bulging was proposed to fabricate micro feature on copper foil. In this process, liquid medium water was used as a soft punch, rubber layer with thickness of 200 μm was used to squeeze liquid medium, and laser shock wave was used as driving force. Forming depth, surface quality, thickness thinning ratio, and cross section micro hardness were investigated under different laser energies. Experimental results showed that the forming depth and surface roughness increased with the laser energy. However, the surface roughness increased slightly with the increase of laser energy, and no thermal response area was found at forming area. Maximum thickness thinning occurred at the fillet when laser energies were 565, 835 and 1200 mJ, while fracture occurred at the bottom area (not the apex) when the laser energy increased to 1380 mJ. Hardness test indicated that, when the material was in cold-rolled, the hardness along the cross-section of the formed area showed an irregular trend. When the material was changed with copper foil annealed at 450 °C, the hardness improved remarkably.

Micro-scale laser dynamic flexible forming (μLDFF) is a new kind of high velocity forming (HVF) process, which uses laser shock wave pressure to realize thin metal sheets micro-forming. Rebound effect usually occurs when forming deep complex micro-features, which has a significant effect on the forming precision. This work firstly investigates the impact and rebound behaviors of workpiece in μLDFF with rubber medium to probe the main affecting factors of rebound effect, then proposes a new μLDFF with plasticine medium to reduce the rebound effect. With the increase of laser energy, the average surface roughness of impact-affected zone (IAZ) reduces firstly by flattening behavior, and then increases afterward due to coining-like operation. The 3D deviation analyses between workpieces and micro-die are performed to characterize the fitability. When laser energy is 675 mJ, bottom region of workpiece fits well with the micro-die. When laser energy is increased to 1020 mJ, bottom region of workpiece separates from the micro-die due to rebound effect. A finite element model considering the machining marks on micro-die surface is built, and the predicted results are validated by experimental results. Coefficient of restitution (COR) and the rebound ratio (α) are used to investigate the impact and rebound process. The results show that rebound effect is dominated by laser energy, surface morphology of micro-die, and loading duration. To effectively reduce the rebound effect, the plasticine layer is first introduced as pressure-carrying medium in this work. The deformation behavior of plasticine medium is like a Reiner-Rivlin fluid. So the plasticine medium closely contacts with the sample during forming, this is equivalent to indirectly increasing the stiffness of sample and prolonging the loading duration. In addition, the plasticine layer can absorb impact-induced reflection wave. So plasticine medium can effectively improve the forming precision.