Improved wettability and mechanical properties of metal coated carbon fiber-reinforced aluminum matrix composites by squeeze melt infiltration technique

In order to improve the wettability and bonding performance of the interface between carbon fiber and aluminum matrix,nickel-and copper-coated carbon fiber-reinforced aluminum matrix composites were fabricated by the squeeze melt infiltration technique.The interface wettability,microstructure and mechanical properties of the composites were compared and investigated.Compared with the uncoated fiber-reinforced aluminum matrix composite,the microstructure analysis indicated that the coatings significantly improved the wettability and effectively inhibited the interface reaction between carbon fiber and aluminum matrix during the process.Under the same processing condition,aluminum melt was easy to infiltrate into the copper-coated fiber bundles.Furthermore,the inhibited interface reaction was more conducive to maintain the original strength of fiber and improve the fiber−matrix interface bonding performance.The mechanical properties were evaluated by uniaxial tensile test.The yield strength,ultimate tensile strength and elastic modulus of the copper-coated carbon fiber-reinforced aluminum matrix composite were about 124 MPa,140 MPa and 82 GPa,respectively.In the case of nickel-coated carbon fiber-reinforced aluminum matrix composite,the yield strength,ultimate tensile strength and elastic modulus were about 60 MPa,70 MPa and 79 GPa,respectively.The excellent mechanical properties for copper-coated fiber-reinforced composites are attributed to better compactness of the matrix and better fiber−matrix interface bonding,which favor the load transfer ability from aluminam matrix to carbon fiber under the loading state,giving full play to the bearing role of carbon fiber.

Integrated Modeling of Process–Microstructure–Property Relations in Friction Stir Additive Manufacturing

Friction stir additive manufacturing is a newly developed solid-state additive manufacturing technology.The material in the stirring zone can be re-stirred and reheated,and mechanical properties can be changed along the building direction.An integrated model is developed to investigate the internal relations of process,microstructure and mechanical properties.Moving heat source model is used to simulate the friction stir additive manufacturing process to obtain the temperature histories,which are used in the following microstructural simulations.Monte Carlo method is used for simulation of recrystallization and grain growth.Precipitate evolution model is used for calculation of precipitate size distributions.Mechanical property is then predicted.Experiments are used for validation of the predicted grains and hardness.Results indicate that the average grain sizes on diff erent layers depend on the temperature in stirring and re-stirring processes.With the increase in building height,average grain size is decreased and hardness is increased.The increase in layer thickness can lead to temperature decrease in reheating and re-stirring processes and then lead to the decrease in average grain size and increase of hardness in stir zone.