Due to the frequent occurrence of Enteromorpha prolifera "green tide" in recent years, how to solve the ecological disaster brought by the green tide and make maximal use of the Enteromorpha prolifera have become an urgent problem. In order to realize the resource utilization of marine biomass, we extract nanofibrillated cellulose (NFC) with high aspect ratio from Enteromorpha prolifera. Filamentous NFC is successfully extracted at nanometric scale with a diameters range of 20~40 nm, a length of several microns, and a crystallinity index of 57.2%. Then NFC/polyvinyl alcohol (PVA) composite films were prepared with NFC as fillers. In addition, for comparison, nanocrystals cellulose (NCC) with small aspect ratio was isolated from microcrystalline cellulose (MCC) to prepare NCC/PVA composite films. It is shown that because Enteromorpha proliferata NFC has a higher aspect ratio, it is easier to interpenetrate with PVA to form a dense network, and the lower concentration ensures the better dispersion of NFC in the matrix, so its enhancement effect on PVA composite films is better than that of NCC. When the NFC content was 0.1 wt %, the light transmittance of NFC/PVA composite film could reach more than 94%, and the swelling degree was 250%, which is 29% lower than that of the pure PVA film, the water resistance was improved. At the same time, the tensile strength, elastic modulus and toughness were 99.1%, 1547% and 117.9% respectively, which are higher than those of PVA.

Currently, the single-point incremental forming process often faces issues such as insufficient formability of the sheet metal and low strength of the formed parts. To address this problem, this study proposes a pre-aged hardening single-point incremental forming (PH-SPIF) process that offers several notable benefits, including shortened procedures, reduced energy consumption, and increased sheet forming limits while maintaining high mechanical properties and geometric accuracy in formed components. To investigate forming limits, an Al-Mg-Si alloy was used to form different wall angles during the PH-SPIF process. Differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) analyses were conducted to characterize microstructure evolution during the PH-SPIF process. The results demonstrate that the PH-SPIF process can achieve a forming limit angle of up to 62°, with excellent geometric accuracy, and hardened component hardness reaching up to 128.5 HV, surpassing the strength of the AA6061-T6 alloy. The DSC and TEM analyses reveal numerous pre-existing thermostable GP zones in the pre-aged hardening alloys, which undergo transformation into dispersed β” phases during the forming procedure, leading to the entanglement of numerous dislocations. The dual effects of phase transformation and plastic deformation during the PH-SPIF process significantly contribute to the desirable mechanical properties of the formed components.