Research on the Secondary Forgeability of High Volume Fraction Whisker Reinforced Aluminum Matrix Composites of Original Squeeze Casting

The poor formability of high volume fraction whisker reinforced aluminum matrix composites of original squeeze casting is an important factor restricting its further development and application. Currently, there are no reports on the secondary forgeability of aluminum matrix composites of original squeeze casting, although some papers on its first forgeability are published. The secondary forgeability is very important for most metals. This study aims to investigate the secondary forgeability of aluminum matrix composites. In this study, the secondary upsetting experiments of 20 vol% SiCw + Al18B4O33w/2024Al composites, treated by the original squeeze casting and extrusion, were carried out. The first upsetting deformation is close to the forming limit, the secondary upsetting deformation under the same deformation conditions was carried out to investigate the secondary forgeability. The experimental results show that, unlike aluminum alloys, the 20 vol% SiCw + Al18B4O33w/2024Al composites at the original squeeze casting and extrusion states have no secondary forgeability due to the whisker rotating and breaking during the secondary upsetting. The high volume fraction whisker reinforced aluminum matrix composites of original squeeze casting cannot be formed by the multiple-forging method since the cavities and cracks caused by whisker fracture continue to expand during secondary processing, which leads to further extension of macroscopic cracks.

Study On The Edge Defects of High Volume Fraction 70% SiCp/Al Composites In Ultrasonic-Assisted Milling

Directing at the hard machinability of high volume fraction 70% SiCp/Al composites，a longitudinal and torsional ultrasonic-assisted milling method is proposed to improve the edge quality and machining efficiency. By observing the metallographic structure of the material, the three-dimensional finite element model of SiC particles with spherical, ellipsoidal and random polyhedra is established and analyzed by ABAQUS simulation software. The formation mechanism of edge defects, stress distribution, defect characteristics and the effect of machining parameters on milling force are investigated during ultrasonic-assisted milling. The results show that the edge defects appear at the inlet, outlet and middle edge position, especiallyis more serious at the outlet position. The SiC particles failure modes mainly include particle pullout, particle shearing, crushing, and the edge defects mainly include matrix tearing, edge breakage, burrs, bulgesandpits. In a certain range of ultrasonic amplitude, ultrasonic-assisted milling can effectively reduce the surface fragmentation rate and milling force, slow down the expansion of cracks, increase the plastic flow of material, and obtain better edge quality compared with traditional machining method. By comparing the results of finite element simulation and experimental tests, it shows that the simulation results are in good agreement with the experimental tests.

Study on Meso-scale Grinding Surface Roughness and Sub-surface Quality of High Volume Fraction SiCp/Al2024 composites

In order to improve the surface grinding quality of high volume fraction aluminum matrix composites, the cutting tool models with different rake angles are established, the grinding process is simulated, and the material removal mechanism and the broken state of SiC particles are obtained. Through single factor experiment, the 60% volume fraction SiCp/Al2024 composites are ground by diamond grinding rod with 3mm diameter, the surface roughness (Ra) is measured, and the surface and sub-surface quality of SiCp/Al2024 composites with meso-scale grinding is investigated. Meanwhile, the influence mechanism of grinding depth (ap) on surface quality is put forward, and the influence of different grinding depth on the fragmentation of SiC particles in sub-surface layer is discussed, which verifies the correctness of grinding simulation. The relevant research and theoretical model are of great significance to the study of grinding properties of composite materials.

Study on the High-Speed Milling Performance of High-Volume Fraction SiCp/Al Composites

Compared with other materials, high-volume fraction aluminum-based silicon carbide composites (hereinafter referred to as SiCp/Al) have many advantages, including high strength, small change in the expansion coefficient due to temperature, high wear resistance, high corrosion resistance, high fatigue resistance, low density, good dimensional stability, and thermal conductivity. SiCp/Al composites have been widely used in aerospace, ordnance, transportation service, precision instruments, and in many other fields. In this study, the ABAQUS/explicit large-scale finite element analysis platform was used to simulate the milling process of SiCp/Al composites. By changing the parameters of the tool angle, milling depth, and milling speed, the influence of these parameters on the cutting force, cutting temperature, cutting stress, and cutting chips was studied. Optimization of the parameters was based on the above change rules to obtain the best processing combination of parameters. Then, the causes of surface machining defects, such as deep pits, shallow pits, and bulges, were simulated and discussed. Finally, the best cutting parameters obtained through simulation analysis was the tool rake angle γ0 = 5°, tool clearance angle α0 = 5°, corner radius r = 0.4 mm, milling depth ap = 50 mm, and milling speed vc= 300 m/min. The optimal combination of milling parameters provides a theoretical basis for subsequent cutting.