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 HV0.2, which was 6.49% higher than the HEA without controlled.
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.
Due to the high manufacturing cost of Nickel based alloy compressor blisks, aero engine repairing process research has important engineering significance and economic value. Inconel718 Ni-based superalloy has the advantages of irradiation, corrosion resistance and excellent mechanical and processing properties. In this paper, a production process for the laser additive and subtractive hybrid manufacturing technologies was presented to repair a microcrack of Inconel 718. The whole repairing process includes four steps. Firstly, a pulsed laser was used to clean and etch the crack through materials subtractive. Secondly, a high-power continuous wave laser was used to additive material in the crack by laser deposition. Thirdly, a pulsed laser was applied to remove the excess repair material. Finally, a fiber laser was used to polish surface. The results showed that defect-free repair samples can be obtained with proper processing parameters. Metallurgical bonding could be achieved between the melting Inconel718 powder and the substrate under the action of a high-energy laser beam. The columnar dendrite and inter-dendritic structure in the repair zone are epitaxially grown along the deposition direction. The microstructure in the repair zone was fine and uniform due to the high gradient, high-speed solidification characteristics of the laser rapid fusion. The micro-hardness of the repaired tissue reduced to about 87% of the matrix and there was no new phase produced in the repair zone.