Study On The Design And Preparation Of Biomimetic Light And High Strength Of Al-B₄C Composite Materials

In aviation,spaceflight,navigation,transportation,energy,national defense,and many other engineering field,the material under the condition of high temperature,high speed,high load ability to service demand is higher and higher,which requires engineering materials with light weight,high strength,anti-crack,abrasion resistance,impact resistance and other mechanical properties.It also puts forward for engineering materials higher and more stringent requirements in the design and preparation.Engineering materials have a variety of promoting mechanical performance structure bottlenecks and the optimal material selection problem.Nature quietly open the door for us with the most reliable,most efficient and economic method to solve the problem.The study found that the most of materials with excellent comprehensive mechanical properties possess coupling structures which are in the form of"soft and hard","strong and tough"and"firm and flexible".Therefore,exploring the biological materials"soft and hard","strong,toughness","firm,flexible"coupling structure characteristics and regularity of energy efficiency and revealing its"light,strong,firm,toughness"the realization of the feature model function will provide effective bionic new ideas and new technologies for the traditional engineering materials designed.Solving the technical bottleneck of existing materials comprehensive performance has important research significance.Therefore,this thesis makes Rapana venosa and Meretrix meretrix linnaeus with the lightweight,high strength,excellent impact resistance performance act as the bionic model.Based on the shell of light weight,high strength,crack arrest principle,a kind of bionic light weight,high strength,impact resistant composite materials of B₄C/5083 Al system is fabricated by hot pressing sintering technology,which will provide a new concept,new way of thinking in improving ceramic reinforced aluminum matrix composite material strength and toughness together.The research contents of this thesis are as follows:（1）the Rapana venosa shell is a typical three-layer structure,the outermost layer is the horny layer,and the middle is the prismatic layer,and the innermost layer is the nacreous layer.In the composition,the horny layer is calcite type calcium carbonate ceramics,and the prismatic layer and the nacreous layer are all the calcium carbonate ceramics.On the structure,the horny layer is attached to the prismatic layer.The prismatic layer occupies about 90%of the total thickness,which is divided into laminar lamination and lamellar interleaving structure.The nacreous layer has a lamellar interlocking structure.On the mechanical properties,Rapana venosa presents soft-hard-the most hard distribution pattern.The overall compressive strength is8.41 MPa.Layered cascade and staggered structure have played important roles in toughening and crack deflection.（2）the Meretrix meretrix linnaeus shell is a typical three-layer structure,the outermost layer is the horny layer,and the middle is the prismatic layer,and the innermost layer is the nacreous layer.In the composition,the elements of the horny layer,prismatic layer and the nacreous layer are all of the ceramic calcium carbonate.In the structure,there is a mastoid structure between the horny layer and the prismatic layer,which acts as a bonding strength between the two layers.The prismatic layer is divided into two sections presenting the lamellar overlapping structure,which is full of micropores on the slab structure which has both the light weight effect and the effect of absorbing stress and slow-release impact energy.On the mechanical properties,the microhardness of Meretrix meretrix linnaeus shell presents a"soft-the most hard-a hard"mode of distribution.The average compressive strength is 6.7MPa,and the average bending strength is 296.25 MPa.When shocked,layered structure and microporous can be used to be a toughening and crack deflection and slow releasing stress effect.（3）Based on Meretrix meretrix linnaeus shell and Rapana venosa shell layer structure and hardness distribution patterns,B₄C/5083Al system layer is acted as hard phase,using pure 5083Al acts as soft phase establish the biomimetic layered materials matching mode.Among them,in the imitation Rapana venosa shell structure,10 wt.%B₄C/5083Al system layer acts as Rapana venosa shell horny layer part,20 wt.%of B₄C/5083Al system layer acts as imitation Rapana venosa shell prismatic layer part,30 wt.%of B₄C/5083Al system acts as imitation nacreous layer.For the imitation Meretrix meretrix linnaeus shell structure,10wt.%B₄C/5083Al system layer is used as the nacreous layer of the imitation Meretrix meretrix linnaeus shell,and 30wt.%B₄C/5083Al system layer is used to act as prismatic layer,20wt.%B₄C/5083Al system layer is used as the nacreous layer of imitation Meretrix meretrix linnaeus shell.（4）The bionic lamellar impact resistance material was successfully prepared by the method of hot pressing.On the macro level,the biomimetic lamellar impact resistance material has a multi-layered structure,which is composed of B₄C/5083Al composite rigid layer and 5083Al flexible layer,which possess the hardness distribution characteristics of"soft and hard".On the micro level,B₄C/5083Al composite is composed of B₄C hard ceramic 5083Al substrate.B₄C hard ceramic has staggered distribution in the well toughness 5083Al substrate,which has the characteristic of"soft and hard".Imitation shell structure and hardness distribution patterns reappear in the biological engineering materials application.（5）Comparing with 10 wt.%-30 wt.%of B₄C/5083Al system homogeneous composite material,imitation Meretrix meretrix linnaeus shell and Rapana venosa shell structure composite material has higher bending strength,compressive strength,impact toughness and fracture toughness.The bionic structure design makes B₄C/5083Al system better mechanical properties.（6）Under bending,compression,impact load,structural layer of imitation Meretrix meretrix linnaeus shell and Rapana venosa shell structure composites can reset the extension direction of crack in the next layer.Crack deflection and slowing down the crack extension will present during the loading.At the same time,in the composite material system,the hard phase bears the load and the soft phase absorbs and the sustained release stress,which characteristics of the rigid soft combination make the material strength and toughness simultaneously increases.