The Fabication And Characterization Of Magnesium Matrix Composite Reinforced With Nitride Or Boride

Magnesium alloys containing Gd have been studied extensively due to their strong precipitation hardening behavior.To gain a better mechanical property,One way is to add microalloying elements to promote the formation of fine precipitates,while another effective approach is to induce thermally stable nanoparticles to reinforce the matrixThe research focused on synthesizing boride or nitride by in-situ reaction and fabricating magnesium matrix composite with excellent mechanical properties.The MgB₂ particles reinforced magnesium matrix composite was fabricated with sintered Mg-MgB₂ intermediate alloy into Mg melting,and the copper facilitated the in-situ synthesis of MgB₂ compared with zinc.There were myriads of hexagonal MgB₂ particles in the middle of Mg grains of fabricated composite with Mg-B-Cu system.Besides,the MgB₂ could act as nuclei in Mg solidification process just like Zr element,and facilitate the grain refinement.The boride of MgB₂ and GdB₄ reinforced magnesium matrix composite was fabricated with powder metallurgy,the MMed 12h composite had more a uniform microstructure compared with MMed 9h sample.There were white bulk GdH₂ particles in the magnesium matrix composite with addition of PCA.The MMed 12h composite exhibits great mechanical properties:YTS of 463MPa,elongation of 2.8%.The high strength is attributable to the grain refinement and dispersion strengthening of GdH₂ and GdB₆ particles.A novel bulk Mg-Gd matrix nanocomposite reinforced with GdN nanoparticles has been successfully fabricated utilizing an advanced powder metallurgy route within in-situ reactions during sintering process.The as-prepared nanocomposite with nanocrystalline?NC?or ultrafine-grained?UFG?matrix and homogeneously dispersed nanoparticles exhibits phenomenal mechanical properties:UTS of 521 MPa,YS of 506 MPa and elongation of 2.8%.The drastic improvement of the strength in comparison with that of conventional magnesium alloys is ascribed to fine grain strengthening of NC/UFG matrix,dispersion strengthening and load bearing mechanism of the GdN nanoparticles and??Mg₅Gd?or?'?Mg₃Gd?precipitates.