Study On Mechanical Properties Of Ti_f/Al Composites Based On Impact Toughness

Considering the rover wheel rim applications as the background, this paper designed and fabricated unidirectional TC40.1/5056 composites and 2D-Tif/Al composites in order to meet impact resistance, crack resistance, wear-resistant and lightweight requirements. The strength and ductility of titanium fiber is relatively higher compared to those metal fibers, parameters such as reinforced titanium fiber whether coated, density of fiber were designed to explore the effect to mechanical properties of composites in this paper. OM, XRD, SEM, EDS, TEM were used to observe the microstructure of Tif/Al composites.2D-Tif/Al composites were prepared by pressure infiltration. The effect of lay out of fiber direction(0°-90°, 15°-75°, 30°-60° and ±45°), titanium fiber types and matrix alloy(2024 and 5056) were studied to observe the change about strength and toughness of 2D-Tif/Al composites. It found that when the fiber lay in the direction ±45°, the strength and ductility of the composites perform ed best. when choose matrix alloy 5056, the ductility and impact toughness of the composites have been improved because the higher plasticity and less interface reaction compared to the 2024 aluminum matrix.Longitudinal tensile strength and elongation of unidirectional TC40.1/5056 composites are 481 MPa and 9%. The tensile strength of different angles(60°, 45°and 90°)was tested and turned out to be 135 MPa, 121 MPa and 105 MPa respectively, the elongation of all these composites is less than 1%. But the tensile strength of all directions in line with Tsai-Hill intensity prediction.The bending strength of unidirectional TC40.1/5056 composites(0°direction) can be 800 MPa and more, but ± 45° lay out of 2D-TC40.1/5056 composites is about 400 MPa. Bending strength of two-dimensional network composites is only about 50% of its unidirectional composites, mainly because the effect of fiber reinforced in vertical span direction can not be reflected, and the interface reaction will play fragmented role in composites, leading to the overall decline bending strength of two-dimensional TC40.1/5056.The impact process of unidirectional TC40.1/5056 composites(0°direction) consists of four stages, including the elastic deformation of the titanium fiber together with matrix alloy in linear elastic deformation stage, the matrix is brittle with respect to titanium fiber and then crack initiation started, leading to a certain stress released until matrix broken, after that, the fiber still keep elastic deformation before the fiber plastically deformed, finally, the fiber broken and corresponding the fracture of composites. The impact toughness is 271KJ/m2. However, the ± 45° lay out of 2D-TC40.1/5056 composites is 371KJ/m2, mainly due to the delamination appeared during the impact process, inceasing the crack propagation path and then increasing their impact toughness.Titanium fiber will reduce the mechanical properties of composite materials like the shear strength, tensile strength, flexural strength and impact toughness when surface coated with carbon. Mainly carbon could react with titanium easilyier rather than aluminium. The crack can be seen in the interface, so the bonding strength is relatively low. Uncoated fiber-reinforced aluminum matrix composite has higher shear strength, which means the interface binding is better, and separation occurred easily when applied the external load. The matrix alloy improved the resistance to external load capacity of the composite material due to a large number of precipitates, the matrix alloy is easy to form pores in these places, adjust more deformation, increasing the absorption of deformation energy, so the toughness of the material improved.It discovered that composites with higher density of fiber have stronger external load resistance. Smaller diameter of titanium fiber will have much more interface when have same volume in the composite material. TA20.1/5056(31%) composites yield strength is about 100 MPa, tensile strength is about 120 MPa and elongation of 4%, the impact toughness is 265KJ/m2. However, yield strength of TA20.05/5056 Composites(31%) is up to about 150 MPa, with tensile strength of 270 MPa, the elongation can reach 4.5%, impact toughness 371 KJ /m2.