The Research On The Technics Of Cyclic Pressing In The Densification Of Large-dimension Ring Of Al-20%Si/SiC_p

Large-dimension rings of metal matrix composite have been broadly used in many fields such as war industry,spaceflight,automobile and other industry.At present,preparing big size rings has been an important subject of material processing technology domain.As an advanced material preparation technology, Spray Deposition has been widely used to produce alloys and metal matrix composites. However, the spray deposited preforms usually contain more than 10vol.% porosity that is a great disadvantage for the mechanical properties. In order to prepare full density products of high mechanical performance, the porous preforms must suffer densification process. Cyclic pressing is a new kind of densification processing, which is introduced to densify as-deposited ring of Al-20%Si/SiCP.This paper includes the densification result and rule of this technics.The research shows that this technics can be successfully used to densify spray-forming porous material and can be availably adopted to improve mechanical performance and microstructure. This technics is characterized by simple equipment,small expense and flexible process,and these characters will make it come true to producing spray-deposited rings less costly.The main conclusions are drawn as follows:(1) For spray-forming ring of little thickness,densification results including friction mechanical property were investigated.After single-direction cyclic pressing,in the region near processing face,cavities close well and mechanical performances are better than those of region far from processing face. Compared with those of as-sprayed ring,hardness and tension strength of area near processing face are increased by 45% and 40% respectively.Friction mechanical performance of the ring is improved at large extent,and especially the wearing amount is merely 13% of as-sprayed rings.After dual-direction cyclic pressing,the pore-closed state and the distributing of density and hardness are nearly identical in every part of ring.The friction mechanical property is close to that of single-direction-cyclic-press ring.(2) For the cyclic pressing technics,the thickness of densified layer of ring was studied,and the rules which the technics must follow had been investigated,and the influence of parameter on densification results had also been investigated. According to the theory of rolling,the conclusion of thickness of densification layer had been drawn for the dual-direction cyclic pressing.The term that decreased height of one stage and distance of one step advancing had been researched. After single-direction cyclic pressing,the distributing of density and hardness...