Study On Process And Properties Of CNTs/Al Composites By Rotational Friction Extrusion

Aluminum matrix composites reinforced with4.1~11.6vol%multi-walled carbonnanotubes (MWCNTs) were prepared by rotational friction extrusion method (RFEM).The effect of tools rotation speed on macro morphology was investigated. Themechanical properties of the composite were tested. The influence of content ofMWCNTs on the hardness and tensile strength was analyzed. Some phases of thecomposite were analyzed by X-ray diffraction. The microstructures and interface ofthe composite were observed by TEM. Further the strengthening mechanism of thecomposites was studied. The main results show that as following:MWCNTs/Al composites were successfully prepared by RFEM. Rotation speedof the tool is great influences on shaping of the composite. The compact MWCNTs/Alcomposite materials can be obtained when the rotation speed is750r/min.The content of MWCNTs is great influences on the hardness and tensile strengthof the composites. With the increasing of the content of MWCNTs, the hardness andtensile strength of the composites were increased. Tensile strength of the composite is202.4Mpa, which is1.82times of aluminum by RFEM when the content of MWCNTsis8.3%. Macroscopic fracture was characterized by brittle fracture. Tensile strength ofthe composite is190.8Mpa, which is1.71times of aluminum by RFEM when thecontent of MWCNTs is5.8%. The fractures of the composite materials show ductilefracture on macro.The interface reaction occurred between aluminum and MWCNTs which wereprepared by RFEM. The reaction product is Al4C3. And TEM observations show thatsome of Al4C3phases which were formed a thin layer coated on the outer wall ofMWCNTs. The thickness of the thin layer is11nm to13nm. A few thin layer of Al4C3on the interface of MWCNTs and aluminum has played a certain role in the wetting.And the thin layer enhanced the interfacial bonding between MWCNTs andaluminum.The interface reaction products is Al4C3between the Al and C in MWCNTs/Alcomposites which were prepared by RFEM. The interplanar spaced is0.827nm. Thecrystal plane is (003). The interplanar spaced of aluminum is0.241nm. The crystal plane is (111). The interplanar spaced of MWCNTs is0.343nm.The crystal plane is(002). There is a better interface combination among the three planes. It’s anon-coherent interface. There are crystallographic orientation relationship ofMWCNTs (002) parallel to Al4C3(003) at the interface after Fourier transform.