Preparation,Microstructure And Properties Of Fe/Fe₂Al₅ Layered Composites Toughened By Aluminum Matrix Continuous Fiber

Aluminum matrix continuous fiber toughened Fe/Fe₂Al₅layered composite is a new type of composite material,which is inspired by the structure toughening mechanism of shell pearl layer and applied the idea of bionics to material design.It belongs to metal-intermetallic layered composite(MIL composite).MIL composites are widely used because of their excellent properties such as high strength,high specific modulus,high hardness and low density.At present,Ti-Al system,Ni-Al system and Fe-Al system are commonly studied on MIL composite materials.However,due to the high hardness and high brittleness of the strong layer,the overall brittle material is presented.Therefore,the study on toughening methods of MIL composite materials is gradually emerging,among which the most common toughening method is fiber toughening method.At present,the fiber toughening method has been seen in Ti-Al and Ni-Al systems,but there are few reports on the fiber toughening of Fe-Al system,and the continuous nickel-plated carbon fiber toughening has not been studied,so this topic chooses nickel-plated carbon fiber as the toughening material to study the preparation and microstructure properties of continuous fiber toughening Fe/Fe₂Al₅layered composites.In this paper,the continuous short-cut nickel-plated carbon fiber felt,1060Al foil and pure iron foil were pretreated,and then the aluminum matrix continuous carbon fiber composite preform was prepared by vacuum hot pressing sintering furnace at 630 and 650?under 21 and 28MPa pressure.The Fe/Fe₂Al₅laminated composite with aluminum matrix continuous fiber toughened was prepared at 658?and 10MPa by alternating lamination reaction between the preform with the best comprehensive performance and pure iron foil.The effect and toughening mechanism of carbon fiber on aluminum matrix continuous fiber reinforced Fe/Fe₂Al₅laminated composites were analyzed.The microstructure,structure,phase composition,and physical and mechanical properties of the laminated composites were analyzed.The results show that:(1)The nickel plating layer on the surface of carbon fiber improves the wettability of the interface between aluminum and carbon fiber,and the Al matrix is fully permeated to form the aluminum matrix continuous fiber toughened Fe/Fe₂Al₅lamellar composite with good interface bonding.The nickel plating layer reacts with the aluminum matrix near the carbon fiber to generate Al₃Ni,which effectively prevents the brittle phase Al₄C₃formed between the aluminum matrix and carbon fiber,and a small amount of Al₅Fe Ni strengthens the precipitated phase.(2)The addition of carbon fiber can effectively improve the physical and mechanical properties of the preform,and reduce the density.The main products of Fe/Fe₂Al₅laminated composites toughened by aluminum matrix continuous fiber are Fe₂Al₅phase and a small amount of Fe₃Al1₄and Al₅Fe Ni phase.The addition of continuous fibers eliminates the Central Line of traditional MIL materials and instead forms an interface between carbon fiber and Al-Fe₂Al₅.(3)With the increase of the reaction time,the thickness of the Fe₂Al₅phase of the intermetallic compound layer formed by the reaction of Al and Fe increases,and the tongue shape and a small number of island particles are formed near the iron side.The growth of Fe₂Al₅phase is controlled by bulk diffusion and shows a parabolic growth law.(4)The samples with the density of 4.376g/cm~3,5.100g/cm~3and 5.602g/cm~3were prepared by using iron foil of different thickness.The hardness of aluminum matrix is45±5HV,the hardness of iron matrix is 180±10HV and the hardness of intermetallic compound layer is 800±150HV.(5)Dynamic compression shows that the ultimate compressive strength range is492.31-801.79MPa,and the strain rate range is 3700-5600/s.The real stress-strain diagrams all have a yield platform.Dynamic compression fracture includes cleavage fracture and micropore aggregation fracture.(6)The failure of the tensile stress-strain curve is stepped,and the tensile strength increases with the decrease of intermetallic compound and the increase of foil thickness.Under the condition of holding for 1h,the elongation increased by 66.7%when the thickness of iron foil increased.The specimens with 0.8mm iron foil held for 1 hour had the best tensile properties,with tensile strength of 345.57 MPa and elongation of 0.45.With the addition of carbon fiber,the elongation and tensile strength of the composites increased by 15.4%and2.7%respectively.