Design, Preparation And Properties Of Al-Based Energetic Structural Materials With Low Reaction Threshold

Efficient damage is the core direction of weapon equipment development.Al-based energetic structural materials（Al-ESMs）are characterized by the integration of structure and energy,and their application in ammunition is a new way to improve the damage power of existing weapons and equipment.However,the reaction threshold of Al-ESMs is high,which makes it difficult to react and release energy at a low impact velocity.Aiming at the problem of high reaction threshold of Al-ESMs,this thesis intends to add CuO with different contents and particle sizes to promote energy release of the intermetallic reaction and the oxidation reaction with oxygen through the formation of pre-reaction hot spots in the material by the heat release of thermite reaction.It is planned to add W with different contents to regulate the mechanical properties of materials and improve the crushing behavior of materials during high speed impact,and finally achieve the goal of reducing the reaction threshold and improving the energy release efficiency of Al-ESMs.This thesis systematically studied the effects of CuO content,particle size and W content on microstructure,mechanical properties,thermal reaction characteristics and high speed impact response characteristics of materials,the main conclusions are as follows:Al-ESMs with different compositions were prepared by hot pressing process.The effects of CuO content,particle size,W content and sintering temperature on the microstructure and mechanical properties of the materials were studied.The results show that CuO content and particle size have little influence on the relative density of Al-ESMs within a certain range,and adding CuO with appropriate content and particle size can improve the strength and brittleness of Al-ESMs.When CuO content is 4wt.%and particle size is 1-3μm,the maximum tensile strength of the material is 301.0MPa.However,if CuO content is too high or the particle size is too small,the mechanical properties of the Al-ESMs will decrease due to the increase of weak bonding surface.In addition,due to the high melting point and low plastic of W,the addition of a certain amount of W will reduce the relative density and quasi-static mechanical properties of materials.In terms of sintering temperature,sintering at 470℃（compared with 420℃）is beneficial to the improvement of relative density and quasi-static mechanical properties,but in this sintering process,atomic diffusion between CuO and Al generates complex Cu-Al-O phase,which changes the existence form of CuO.On this basis,differential scanning calorimeter（DSC）,X-ray powder diffraction（XRD）and scanning electron microscope（SEM）were used to study the thermal reaction characteristics of Al-ESMs with different compositions.The analysis shows that the thermal reaction threshold of Al-ESMs can be effectively reduced by adjusting the content,particle size of CuO and the content of W.The thermal reaction threshold of Al-ESMs with CuO content of 6wt.%and particle size of 10μm is 52℃lower than that of Al-ESMs without CuO,and the thermal reaction tends to generate Al Ta phase with higher heat release.The thermal reaction threshold of Al-ESMs with CuO content of 4wt.%and particle size of 3-5μm is 92℃lower than that of Al-ESMs without CuO.However,when the CuO particle size is too small,the control of thermal reaction threshold of Al-ESMs is seriously unfavorable due to interfacial diffusion and agglomeration.In addition,the alloying reaction between W and Al tends to occur at a lower temperature to generate Al₄W and release heat,which reduces the thermal reaction threshold of the material and consumes a large amount of Al,thus reducing the degree of alloying reaction between Al and Ta.Finally,the high speed impact crushing behavior and energy release characteristics of Al-ESMs were studied by ballistic gun experiment at impact velocity of about800m·s^-1.The results show that the addition of appropriate amount of CuO makes Al-ESMs more conducive to the formation of fine debris clouds with high temperature during high speed impact,which makes the larger debris react in this process,and thus reduces the impact reaction threshold of materials.The quasi-static pressure peak of Al-ESMs with CuO content of 6wt.%and particle size of 10μm can reach 0.1081MPa at about 800m·s^-1velocity,which is 47.68%higher than that of materials without CuO under the same condition.However,CuO particle size has little effect on the impact energy release of Al-ESMs.In addition,the addition of an appropriate amount of W can change the mechanical properties of Al-ESMs so that the materials are more likely to form fine debris clouds during high speed impact,thus improving the energy release characteristics of materials and achieving high energy release at a low impact speed.The Al-ESMs sintered at 470℃are difficult to form effective thermite reaction zone due to the formation of Cu-Al-O phase,and the solid solution of Cu atoms in the Al matrix improve the strength of the material and makes it difficult to form fine debris cloud during high-speed impact.Therefore,the Al-ESMs prepared at 420℃have the lower impact reaction threshold.