Fabrication,Dynamic Compressive Properties And Impact Resistance Mechanism Of Laminated Impact Resistance Ceramics

The low melting point and low hardness of metals,as well as the brittleness and low damage tolerance of ceramics,make metals and ceramcs not resist multi-hit and highspeed/high-energy impact.The laminated ceramics with high damage tolerance,high energy absorption capacity and well structural designability could meet all the requirements of impact resistance concept,but the reseaches almost focus on laminated impact resistance ceramics with weak interfaces of porous ceramics or weak materials.However,the failure mode of the laminated ceramics fabricated by tranditional methods under impact are almost interfacial failure or delamination,due to weak interfaces and weak bonding strength of interfaces,which reduce the structural integrity and energy absorption capacity.Two novel methods,reactive hot pressing?RHP?and reactive jointing method?RJM?,were proposed to fabricate soft and hard interbedded laminated ceramics with microstructural designability during fabrication process.To optimize the sintering condition for dense laminated ceramics;research the method for designability of interfaces and controllability of inner-layer microstructure;studied the relationship between the microstructure and the mechanical properties of the laminated ceramics;investigated the microstructure of the laminated ceramics on the dynamic compressive properties;investigated the effects of the properties of ceramic and metal layers on the dynamic properties of M/C laminated ceramics.Finally,comparing the dynamic properties of laminated ceramics fabricated by RHP and RJM,respectively.The main research content and results are as follows:?1?The effect of sintering temperature and sintering pressure on the microstructure and mechanical properties was researched.With increasing the sintering temperature and sintering pressure,the densification and hardness of ZrO-Zr₂ CN and Si₃N₄ layers,as well as,the flexural strength and Young's modulus of laminated ZrO-Zr₂CN/Si₃N₄ ceramics were improved.?2?The effects of thicknesses of Si₃N₄ layers and heating rates on the properties of interfaces and microstructure of laminated ZrO-Zr₂CN/Si₃N₄ ceramics were researched,and the reaction mechanisms at interfaces and in ZrO-Zr₂ CN layers were established.With the increase of thicknesses of Si₃N₄ layers or heating rates,the weak interfaces decreased or transformed to strong interfaces.When the heating rates rised from 10 oC to 17 oC,the continual Zr₂ CN phase in ZrO-Zr₂ CN layers was transformed to Zr-O mixture.?3?The effect of microstructure on the mechanical properties of laminated ZrO-Zr₂CN/Si₃N₄ ceramics was researched.Weak Zr₂ CN interfaces with a thickness of above 9-15 ?m was the main controlling factor on the flexural strength of the laminated ceramics;weak Zr₂ CN interfaces?thinner than 9-15 ?m?or strong interfaces helped to improve the flexural strength and work of fracture?WOF?of the laminated ceramics.Weak ZrO-Zr₂ CN layers with continual Zr₂ CN phase contributed to improve the WOF but decrease Young's modulus.?4?The effect of residual stress between layers on the energy absorption capacity was reseasched.With increasing the residual compressive stress in Si₃N₄ layers,the WOF of laminated ZrO-Zr₂CN/Si₃N₄ ceramics increased.?5?The effect of strain rates on the dynamic compressive properties of laminated ZrOZr₂CN/Si₃N₄ ceramics was investigated.With increasing the strain rates from1.1×103 s-1 to 3.3×103 s-1,the failure strain increased continuously;and the highest dynamic compressive strength was obtained at a strain rate of 2.0×103 s-1;the crack start zones at Zr₂ CN interfaces increased with the strain rates increased.?6?The effects of characterization of interface and matrix layers on the dynamic compressive properties of laminated ZrO-Zr₂CN/Si₃N₄ ceramics were investigated.When the thicknesses of Zr₂ CN interfaces increased from 3⁵ ?m to 25-30?m,the propagation model of impact stress wave in the laminated ceramics transformed from collinear impact theory between three rods to four rods;strong interfaces strengthened the dynamic load capacity and energy absorption capacity but weakened the psuedoplastic deformation capacity;thicker Si₃N₄ layers strengthened the dynamic load capacity and psuedoplastic deformation capacity but weakened the energy absorption capacity.?7?The effects of thickness and species of ceramic and metal layers on the dynamic compressive properties of M/C laminated ceramics were investigated.Thick ceramic layers and strong metal layers both strengthened the dynamic load capacity but weakened the psuedoplastic deformation capacity but weakened the energy absorption capacity;strong ceramic layers strengthened the psuedoplastic deformation capacity and weakened the energy absorption capacity;strong metal layers strengthened dynamic load capacity but weakened the dynamic deformation capacity.?8?Compared both soft and hard interbedded laminated ceramics fabricated by RHP and RJM,respectively,and established the basis of logical application laminated impact resistance ceramics.M/C laminated ceramic fabricated by RJM with low preparation temperature and short production cycle were suitable for low energy impact resistance,as well as,laminated ZrO-Zr₂CN/Si₃N₄ ceramics fabricated by RHP.which characteristiced with high dynamc strength,high psueoplastic defomation and well energy absoption capacity,were suitable for high-speed and high-energy impact resistance.