Preparation And Properties Of Aluminum Alloy Composites By Spark Plasma Sintering

Aluminum matrix composites are widely used in aerospace,ship,automobile and other fields.The acceptance of aluminum matrix composites as engineering materials not only depends on the properties of the composites.But it also depends on cheap,easy to customize technology.With the gradual application of carbon nanotubes?CNTs?,CNTs became a good reinforcing phase for aluminum matrix composites due to its special structure and good mechanical properties.In this paper,6061 aluminum alloy was used as the matrix material,carbon nanotubes?CNTs?as the reinforced phase,powder was mixed by vacuum ball grinding,and 6061Al alloy materials and CNTs/6061Al alloy composites were prepared by discharge plasma sintering?SPS?system.The effects of different processes?temperature,holding time,heating rate?on the properties of pure 6061Al alloy material were studied,and the optimal sintering process was determined.Then the effect of CNTs content on the properties of CNTs/6061Al alloy composites?tensile,hardness,wear resistance,corrosion resistance?was investigated under the optimal process conditions.Firstly,the composite powder of 2.5wt%CNTs was treated with the method of vacuum ball-milling mixed powder,and then it was XRD and Raman analysis.There was no Al₂O₃in the XRD pattern,indicating that the vacuum environment was good in the ball-milling process.Both peak D and peak G appeared in the Raman map of the powder,and peak D was lower than peak G,indicating that the damage to CNTs by ball grinding was not serious and the structure of CNTs was relatively intact.SEM,XRD and Raman spectra were used to characterize 6061Al alloy materials at different temperatures.The density of 6061Al alloy materials at different temperatures and composites with different contents of CNTs were analyzed.The results showed that with the increase of temperature,the density of pure 6061Al alloy materials first increased and then decreased,and the maximum density at 500?was98.9%.When the temperature was between 480?and 520?,the density of aluminum alloy materials exceeded 98%.Compared with pure 6061 aluminum alloy materials,the density of CNTs was relatively decreased when CNTs were mixed,which was caused by the property of CNTs being easily agglomerated.With the addition of 2.5wt%CNTs,the density of the composites reached 97.5%.The effects of different process conditions on the properties of pure 6061Al alloy were studied.The mechanical properties of 6061Al alloy prepared by different processes showed regular changes,and the microhardness first increased and then decreased.The wear resistance of the material,including the average friction coefficient,wear rate is first reduced and then increased.According to the research results,the best sintering process was determined to prepare CNTs/6061 aluminum alloy composites for SPS:the temperature was 500?,the holding time was 4min,the heating rate was 50?/min,and the performance of 6061Al alloy material was the best.At this time,the hardness of 6061Al alloy material is 64.07HV,the average friction coefficient is 0.4786,and the wear rate is 0.006425mm³/N?m.The effects of different CNTs contents on the properties of CNTs/6061Al alloy composites were studied.The results showed that:When adding 2.5wt%CNTs,CNTs/6061Al alloy composites had the best performance.The tensile strength of the composites was 237MPa,vickers hardness was 73.6hv,and nanohardness was0.807GPa.The average friction coefficient and wear rate were 0.3716 and0.00413mm³/N?m,The tensile strength,vickers hardness and nano hardness of6061Al alloy materials were increased by 19.7%,14.9%and 27.75%respectively.The average friction coefficient and wear rate were decreased by 22.3%and 35.7%respectively.CNTs/6061Al alloy composites had the lowest mass loss rate,the highest corrosion resistance,and the best corrosion resistance at the addition of2.5wt%CNTs.