Research On Microstructure And Properties Of PI Particle Reinforced Aluminum Matrix Composites Prepared By Friction Stir Processing

Particles reinforced aluminum alloy matrix composites have widely application prospect in modern engineering due to their excellent specific stiffness,specific strength,fatigue resistance and wear resistance.As a new solid processing technology for fabricating aluminum matrix composites,friction stir processing can refine grains and disperse reinforcing phase particles.In this paper,AA7075 aluminum alloy and polyimide particles are used as the matrix and reinforcing phase,respectively.Polyimide particles reinforced AA7075 aluminum matrix composites are fabricated via friction stir processing technology.The effects of processing pass,rotation speed,traverse speed and plunge depth on the polyimide particles distribution,microstructure of the AA7075 aluminum matrix are studied.The relevant research can further enrich the theoretical system of friction stir processing technology.And the same time,the results certain value for reference to fabricate other metal matrix composites by friction stir processing.Microstructure analysis show that friction stir processing technology can significantly improve the microstructure of AA7075/PI composites.The dispersion of the polyimide particles in the aluminum alloy matrix is improved with the increase of the processing passes.After 5 processing passes,the aggregation of the polyimide particles disappears completely,and the grain in the processing zone is significantly refined.High rotation speed,plunge depth and low traverse speed are beneficial to reduce the agglomeration of the polyimide particles in AA7075 aluminum matrix,promote the uniformity of the AA7075/PI composites structure and eliminate internal hole defects.The microhardness test results of AA7075/PI composites show that high rotation speed,low traverse speed,larger plunge depth and multi-pass processing are beneficial to increase the microhardness of the composites.XRD results show that the addition of polyimide do not cause the change of the aluminum alloy matrix phase.The optimal process parameters are the rotation speed of 1200 r/min,the processing pass of 5 passes,the traverse speed of 30 mm/min and the plunge depth of 0.3 mm.The friction and wear test results show that adding polyimide particles to the AA7075 aluminum alloy can improve the wear resistance.The wear mechanism of the AA7075 aluminum matrix is mainly adhesive wear,and the wear mechanism of AA7075/PI composites is mainly abrasive wear.Tensile experiments results show that the tensile strength of AA7075/PI composites is lower than base materials.High rotation speed,low traverse speed,large plunge depth and multi-pass processing are beneficial to increase the tensile strength of AA7075/PI composites.