查看更多>>摘要：Spherical micro-Ti particle(TiP)-reinforced AZ91 magnesium alloy composites were fabricated by semi-solid stirring assisted ultrasonic vibration,which were then subjected to hot extrusion.The microstructure results showed that the addition of Ti particles refined the grain size and decreased the texture intensity of the as-extruded AZ91 alloy.An Al3Ti phase with a thickness of 100 nm formed at the Ti/Mg interface,which had a non-coherent relationship with the magnesium matrix.The as-extruded 1 vol.％TiP/AZ91 composite exhibited the best comprehensive mechanical properties,with yield strength,ultimate tensile strength,and elongation at break of 366 MPa,456 MPa,and 14.6％,respectively,which were significantly higher than those of the AZ91 alloy.Therefore,the addition of Ti particles can improve the strength and ductility of the AZ91 alloy,demonstrating the value of magnesium matrix composites for commercial applications.
查看更多>>摘要：Magnesium(Mg)alloy is considered as a promising biodegradable implant material but restricted to rapid degradation.Here,the new strategies based on thixomolding process had been explored to utilize the outstanding anti-permeability of graphene nanosheets(GNPs)while inhibit its galvanic corrosion with the matrix,so as to improve the corrosion resistance of com-posites.The agglomerate of GNPs with 0.9 wt％content is the main reason for the deterioration of corrosion performance due to the formation of micro-galvanic corrosion.The grain refinement of composites with 0.6 wt％content had positive effects on the better corrosion resistance.After process adjusting,the unique distributions of GNPs along grain boundaries play a vital role in improving the corrosion resistance.It can be ascribed to the following mechanisms:(Ⅰ)The barriers can be established between the Mg matrix and corrosive medium,hence blocking the charge transfer at the interface;(Ⅱ)The GNPs can effectively promote apatite deposition on the Mg matrix,leading to form dense apatite layers and prevent the further invasion of SBF;(Ⅲ)The GNPs acting as reinforcements exists in the corrosion layer and apatite layer,impede the apatite layer falling off from the Mg matrix.These findings broaden the horizon for biomedical applications in Mg matrix composites to realize desired performances.
查看更多>>摘要：The interfacial microstructures and configurations directly affect the comprehensive properties of the composites,but their interfacial adhesion mechanism is complicated to expound by experimental methods.In this work,based on the stacking sequence of the Mg/Mg2Y interface models,nine different Mg/Mg2Y interface configurations with top site,bridge site,and hollow site(HCP)under Mg1,Mg2,and Y terminations were successfully constructed and systematically explored by first-principles calculations.The results showed that the Mg2Y(0001)surface with Y termination is the most stable when the yttrium chemical potential(△µY)is less than-1.09 eV;otherwise,Mg2Y(0001)surface with Mg1 termination is the most stable.The seven-layer Mg(0001)and eleven-layer Mg2Y(0001)slabs are employed to reflect the bulk-like interior proper-ties.Additionally,the Mg(0001)/Mg2Y(0001)with the Y-HCP stacking has the largest interface thermodynamic stability with the value of 2.383 J/m2 in all interface configurations owing to its largest work of adhesion.In addition,the interfacial energy of Y-HCP stacking is significantly smaller than those of Mg1-HCP when △µY is approximately less than-0.55 eV,showing that it is more stable.The thermodynamic stability of Mg/Mg2Y with Y-HCP is due to Mg-Y chemical bonds formed between Mg and Y atoms.Lastly,the Mg/Mg2Y interfaces are strong interfaces based on the Griffith fracture theory.
查看更多>>摘要：The Tip/ZX60 composites with different Tip contents were prepared by semi-solid stirring casting.After extrusion,the microstructure,work hardening and softening behavior of the Tip/ZX60 composites were analyzed compared with the ZX60(Mg-6Zn-0.2Ca)alloy.The results showed that the addition of Tip could not only promote the nucleation of dynamic recrystallized(DRXed)grains,but also be propitious to the refinement of DRXed grains.With increasing Tip content,the size of DRXed grains decreased accompanied with increasing volume fraction of DRXed grains.As the Tip content increased to 15 vol.％,the average size and volume fraction of DRXed grains reached to～0.32 μm and 93.2％,respectively.Besides,both the strength and elongation were improved by the addition of Tip.With increasing content of Tip,a substantial increase in the strength was achieved with little change in the elongation.However,the elongation decreased sharply when the Tip content further increased to 15 vol.％.The addition of Tip led to an increase in the work hardening rate,which gradually increased with increasing Tip content.However,the softening rate did not demonstrate the same tendency with increasing Tip content.Unlike the conventional ceramic particles,the Tip can be deformed in coordination with the matrix alloy,which imparted a higher softening rate to the matrix alloy.Even though the softening rate improved as the Tip content increased from 5 to 10 vol.％,it dropped deeply as the Tip content increased to 15 vol.％owing to the fracture of Tip during extrusion.
查看更多>>摘要：Graphene reinforced magnesium matrix composites have wide applications in automotive,electronics,aerospace and military fields due to the fascinating mechanical properties.However,it is difficult to realize the high strength and ductility simultane-ously.In this work,the in situ liquid-state method was utilized to prepare GNPs/Mg6Zn composites via CO2/Mg chemical reaction.Tensile strength of the GNPs/Mg6Zn composites was improved with increasing content of the GNPs.Meantime,the composites also exhibit a notable plastic deformation stage,and especially the ductility of 0.12 GNPs/Mg6Zn composites reaches 27.6％.Therefore,this novel preparation method has great potential application for fabricating Mg matrix composites with high strength and high ductility.
查看更多>>摘要：A novel melting infiltration by ultrasonic vibration was investigated and applied to fabricate Ti6A14V(TC4)lattice structure-reinforced Mg-10Gd-2Y-1Zn-xZr(refer to VW92 hereafter,x=0,0.5 wt％)alloy matrix composites.The edge-to-edge matching model indicates that the well-matching and possible orientation relationships(ORs)between the α-Mg and α-Ti,[10-10]α-Mg//[11-23]α-Ti in(0002)α-Mg//(10-10)α-Ti possesses the smallest misfit of 0.4％(fr),and thus the α-Mg grains can nucleate on the TC4 lattice structure.Interfacial reaction occurred in the TC4/VW92+0.5 wt％Zr composites,and the reac-tion product was confirmed to be Al2Zr3,AlZr2 and α-Ti(Zr)particles formed by continuous solution of Zr-Ti.Among the interfacial products,the AlZr2 phase is a brittle phase with high-volume fraction,which is not conducive to the load transfer.But generally speaking,the α-Ti(Zr)and the α-Mg tend to form a coherent interface,which is beneficial for improving the interfacial bonding strength of composites.
查看更多>>摘要：The hybrid of carbon nanotube(CNT)and reduced graphene oxide(RGO)reinforced ZK61 composite was fabricated by a hot extrusion process.Compared with the raw ZK61 alloy and single-reinforced composites,the hybrid-reinforced by RGO+CNT complex exhibited significant enhancements both in mechanical and thermal performance.By adjusting the proportion of RGO and CNT in ZK61 alloy,the obtained optimum ZK61/(0.06 wt％RGO+0.54 wt％CNT)composite exhibited increase of 25.4％in yield strength,26.5％in ultimate tensile strength,104％in failure strain and 30.4％in ther-mal conductivity,respectively,in comparison with ZK61 alloy.The superior properties of the nano-hybrid composite are attributed to the synergetic effects of RGO and CNT,leading to a uniform dispersion and integrated structure as well as the enhanced interfacial bonding with matrix.The strengthening ability of RGO and CNT was calculated to quantify their indi-vidual contribution to the improvement in mechanical and thermal properties of the ZK61 matrix composite.The RGO+CNT hybrids provide a promising way to develop Mg matrix composites with impressive performances.
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