Investigation Of Preparation And Properties Of(CNTs+SiCw)/6061al Composites Synthesised By Squeeze Casting

In this paper,CNTs and SiCw reinforced 6061Al matrix composites were fabricated by squeeze casting,and then extrused the composites.The microstructure and phase of the composites were analysised by the OM,SEM,XRD.The reaction conditions of CNTs and Al were analysised by DSC.At the same time,the tensile and compressed properties,friction and wear property, thermal expansion and damping properties were examined.The observation of SEM showed that CNTs and SiCw were dispersed well in the perform, Squeeze casting was proved to achieve good infiltration of the perform.The analysis of OM shoued that folder aluminum area,uncompleted infiltrated metal area and holes existed in the cast composites,after extrusion, folder aluminum area and uncompleted infiltrated metal area were elongated along the extrusion direction,the number of the holes was reduced,the reinforcement was dispersed more uniformly.It shows that CNTs and SiCw were disperse well after observed the sintered perform by SEM.The compression strength test indicated that the compression strength of the perform which CNTs were plated Ni was higher than CNTs were not plated Ni,and the compression strength of the perform was higher than the critical infiltration pressure between the perform and Al matrix.The interface reactions between CNTs and SiCw occur above or below the aluminum melting temperature,and generatede the Al₄C₃. The reaction activation energy between CNTs and 6061 Al was higher than 2024Al below the aluminum melting temperature.The interface reactions can be controlled below the aluminum melting temperature, under the insulated conditions of 580℃(65min),the interface bond was improved,at the same time,the injury of CNTs was not obvious.Dry friction and wear tests at the room temperature show that applied load on friction coefficient of materials is not obvious, the friction coefficient decreased slowly when the load increases; Wear rate increases rapidly when the load increases. Different degrees of heat treatment on hot extruded composites have great influence on friction and wear properties,thermal insulation material has the best friction and wear properties. The friction and wear properties of the insulated and the insulated aid aged composites significantly better than the aged 6061Al.The wear mechanism can be divided into three stages: mild wear stage, the mechanical mixed layer formation stage (adhesion wear and oxidation wear are important) and the mechanical mixed layer peeling.The compression strength and tensile strength of the hot extruded composites significantly increased after insulation and aging treatment,at the same time the compression and elongation ratio were also increased.The observation of the fraction showed that CNTs aggregates of the extrused,insulated,insulated+aged composites are pretty less.The interface debonding decreased between CNTs and matrix,at the same time the number of the CNTs fraction and dimples were increased.This shows that the increasing of the interface bonding between CNTs and matrix is the main reason that led to the improvement of the mechanical properties.The thermal expansion law of the A, B composite materials where the aggregate amount of carbon nanotubes is different. The quantity of carbon nanotube aggregates are many in the A cast composites,the thermal expansion coefficient became lower after insulation;while the quantity of carbon nanotube aggregates are very few in the B cast composites,the thermal expansion coefficient became higher after insulation.The damp-temperature spectrum of the extrused,extrused+insulated,extrused+insulated+aged composites has the same variation, The damp did not change significantly with temperature below the inflection point temperature (235℃). But the damp increased rapidly with increasing temperature above the inflection point temperature;Under the condition of the same temperature and frequency,the damp of the extrused+insulated,extrused+insulated+aged composites is lower than the simple extrused. Under the condition of the same strain, the damp of the extrused+insulated,extrused+insulated+aged composites is higher than the simple extrused.