【作者】 李响；

【导师】 姜风春；

【作者基本信息】 哈尔滨工程大学 ， 材料科学与工程， 2020， 博士

【摘要】 近年来,由于日益严重的能源危机和环境污染,对高性能轻质结构材料的需求尤为迫切。作为最轻的金属结构材料,Mg及其合金在航空航天、汽车、通信、电子和其他工程结构零件中的应用越来越受到重视。此外,Mg及其合金由于具有良好的阻尼性能,常用于振动、噪声控制和能量吸收。然而,其绝对强度较低、塑性有限和刚度不足等明显缺点,限制了其广泛应用。在过去的几十年中,人们通过向Mg及其合金中引入增强相,成功地提升了其综合性能。针对Mg及其合金的不足,本文首先采用纤维复合设计思想,利用热压烧结法制备出了连续NiTi纤维增强的Mg-3Al-Zn复合材料（shape memory alloy fiber reinforced Mg3Al Zn,SMAFR-AZ31复合材料）。此外,采用层状复合设计思想,并基于瞬时液相（Transient Liquid Phase,TLP）连接工艺制备出了Mg3Al Zn-Ti6Al4V金属层状复合材料（Mg3Al Zn-Ti6Al4V laminated metal composite,AZ31-TC4 LMC）和NiTi纤维增强的AZ31-TC4 LMC（（NiTi_f/AZ31）-TC4 LMC）。对三种复合材料的制备工艺、界面结合、力学性能和阻尼性能进行了系统研究,并对每种复合材料的力学失效形式、增强机制和阻尼机制进行了分析。为揭示SMAFR-AZ31复合材料的界面形成、高阻尼与强韧化机制,对该复合材料进行了微结构表征以及阻尼、拉伸、压缩、弯曲和断裂韧性测试,并对其损伤机制进行了研究。结果发现,经560℃/360min烧结后制备的复合材料中相邻AZ31箔材边界与NiTi_f/AZ31界线已完全消失,纤维与基体结合紧密。在NiTi_f/AZ31界面处形成了宽度为0.1μm～2.0μm的纳米晶-非晶氧化物反应层。复合材料在测试温度为66℃时出现明显的阻尼峰,阻尼因子比同温度下的AZ31合金提高了184%,这归因于NiTi合金增强相中的相转变作用。该复合材料的界面法向抗拉强度为57.6MPa,相比于AZ31/AZ31复合板提高了178.3%。垂直和平行于纤维方向的准静态压缩屈服强度分别比AZ31合金提高了33.3%和249.0%。抗拉强度、屈服强度和断裂应变分别比AZ31合金提高了23%、54%和15.4%。弯曲屈服强度和抗弯强度分别较AZ31合金提升了21.7%和36.6%。断裂韧性较AZ31合金提升了15.3%。经分析,NiTi_f/AZ31界面处形成的氧化物非晶相提高了界面结合强度,从而使得基体载荷可以传递到高强度的NiTi纤维中。此外,NiTi_f/AZ31界面对裂纹尖端的有效钝化作用以及NiTi纤维变形、拔出、断裂及界面脱粘均起到良好的增强、增韧作用。为探究AZ31-TC4 LMC中的界面组织演变、结合、高阻尼与强韧化机制,对制备的复合材料进行了阶段性烧结、界面精细表征以及阻尼、拉伸、压缩、弯曲和断裂韧性试验。结果表明,该复合材料中TC4/AZ31界面处的共晶层在560℃保温300min后完全消失。经此工艺烧结后,TC4/AZ31界面形成了宽度为20～108nm的金属间化合物层和300nm的Mg-O反应层。界面处生成的连续金属间化合物层为密排六方结构的Al_192.40Fe_46.22相,且该相与α-Ti基体存在特定的位向关系即:[1210]Al_192.40Fe_46.22//[1101]α-Ti,（2024）Al_192.40Fe_46.22//（0111）α-Ti。AZ31-TC4 LMC中的AZ31基体具有较强的板织构（Max=31.52）,其织构为{0001}//HPD、<0001>//PLD。该复合材料的室温阻尼因子为0.0111,优于AZ31合金的阻尼性能（0.0081）,这归因于TC4/AZ31界面的界面阻尼机制。该复合材料垂直和平行于叠层方向压缩的屈服强度分别较AZ31合金提高了71.6%和242.1%。抗拉强度和屈服强度均约为AZ31合金的2倍,且其比强度较AZ31合金提高了38.8%。此外,其抗弯强度和断裂韧性分别较AZ31合金提高了33%和129.9%。TC4/AZ31界面极窄的金属间化合物层在力学试验中未发生严重分层,载荷的有效传递致使复合材料的力学性能得到了较大的提升。为阐明（NiTi_f/AZ31）-TC4 LMC中NiTi纤维和TC4箔层的混杂增强机制和高阻尼机制,对其进行了微结构、阻尼、拉伸、压缩、弯曲和断裂韧性研究。结果表明,复合材料结构致密,纤维排布均匀,且无明显宏观缺陷。（NiTi_f/AZ31）-TC4 LMC在测试温度为65℃时出现明显的阻尼峰。相比于该温度下的AZ31合金和AZ31-TC4 LMC,其阻尼因子分别提高了221.9%和96.2%,这归因于NiTi合金增强相中的相转变作用。（NiTi_f/AZ31）-TC4 LMC的压缩性能与AZ31-TC4 LMC基本相当。其抗拉强度较AZ31合金和AZ31-TC4 LMC分别提升了112.7%和4.4%。对于拉伸失效应变,其分别提高了4.2%和44.7%。此外,（NiTi_f/AZ31）-TC4 LMC的抗弯强度分别较AZ31-TC4 LMC和AZ31合金提升了36.4%和81.2%。其断裂韧性较AZ31合金、SMAFR-AZ31复合材料和AZ31-TC4 LMC分别提升了165.7%、130.4%和15.6%。经分析,在混杂机制的作用下,纤维的高韧性与箔层的高强度可以通过界面的载荷传递对复合材料起到有效的强韧化效果。更多还原

【Abstract】 In recent years,the demand and development of high performance light-weight structural materials have become particularly urgent due to the increasingly serious energy crisis and environmental pollution.As the lightest metallic structural material,Mg and its alloys have shown a growing interest for weight critical applications,including aerospace,automotive,communication electronics and other structural engineering parts.Furthermore,Mg and its alloys are commonly used for vibration and noise control as well as energy absorption devices because of their high damping capacity.However,some obvious disadvantages,such as relatively low absolute strength,limited ductility and insufficient stiffness restrict their extensive applications.In the last few decades,the compositing method has been successfully employed to enhance the properties of Mg and its alloys via introducing various reinforcements into the matrix.In this paper,the continuous NiTi fiber reinforced Mg3Al Zn composite（SMAFR-AZ31）was fabricated via vacuum hot pressing sintering based on the design philosophies of fiber reinforcing.Meanwhile,based on the laminate reinforcing and transient liquid phase（TLP）bonding mechanisms,the Mg3Al Zn-Ti6Al4V laminate metal composite（AZ31-TC4 LMC）and NiTi fiber reinforced AZ31-TC4 LMC（（NiTi_f/AZ31）-TC4 LMC）were successfully fabricated.Moreover,the preparation parameters,interfacial bonding mechanism,mechanical and damping properties of the composites were systematically studied,and the mechanical strengthening mechanism,failure modes and damping mechanisms of each composite were analyzed.In order to reveal the interface formation,damping and toughening mechanisms of SMAFR-AZ31 composite,the microstructure characterization,damping,tensile,compression,bending and fracture toughness tests were carried out,and the damage mechanism was studied.The results show that the interfacial bond between NiTi fibers and AZ31 matrix is excellent without visible voids,and the boundaries of the original AZ31 foils disappear completely after 560℃/360min sintering.A nanocrystalline-amorphous reaction layer with a width of 0.1μm～2μm was formed along the NiTi_f/AZ31 interface in SMAFR-AZ31composite.The damping factor of the composite is 184%higher than that of AZ31 alloy at66℃,which is attributed to the phase transformation in the NiTi reinforcement.The normal tensile strength of SMAFR-AZ31 composite is 57.6MPa,which is 178.3%higher than that of AZ31 laminate sheet.The quasi-static compressive yield strengths of the composite are increased by 33.3%and 249.0%when loading perpendicular and parallel to the fiber direction,respectively.The tensile strength,yield strength and failure strain of SMAFR-AZ31composite are 23%,54%and 15.4%higher than those of AZ31 alloy,respectively.The bending yield strength and bending strength of the composite are increased by 21.7%and36.6%compared with AZ31 alloy,respectively.The fracture toughness of the composite is15.3%higher than that of AZ31 alloy.The oxide amorphous phase formed at the NiTi_f/AZ31interface improves the interfacial bonding strength,so that the load can be transferred to the high-strength NiTi reinforcement from AZ31 matrix.In addition,the passivation of crack tip as well as the deformation,pull-out,fracture and debonding of the fiber play an effective role in strengthening the composite.To clarify the microstructure evolution,damping and toughening mechanisms in AZ31-TC4 LMC,the staged sintered and fine characterization of the interface were carried out.In addition,the damping,tensile,compression,bending and fracture toughness of the composite were also tested.After keeping temperature at 560℃for 300 min,it can be observed that the eutectic layer disappeare completely at TC4/AZ31 interface in AZ31-TC4LMC.The TC4/AZ31 interface consists of an intermetallics layer with a width of 20～108nm and a Mg-O reaction layer with a thickness of 300nm.The continuous intermetallics layer is Al_192.40Fe_46.22phase with hcp structure.Besides,the Al_192.40Fe_46.22phase has a specific orientation relationship with theα-Ti matrix:[1210]Al_192.40Fe_46.22//[1101]α-Ti,（2024）Al_192.40Fe_46.22//（0111）α-Ti.For the adjacent AZ31 foils interface in AZ31-TC4 LMC,the secondary recrystallization causes the formation of a secondary recrystallization texture,{0001}//HPD,<0001>//PLD.The damping factor of AZ31-TC4 LMC is～0.0111 under ambient condition,which is better than that of AZ31 alloy（～0.0081）.The improvement of damping property is attributed to the interfacial damping mechanism of TC4/AZ31 interface.The quasi-static compressive yield strengths of the composite are increased by 71.6%and242.1%when loading perpendicular and parallel to the laminate direction,respectively.The tensile strength and yield strength of AZ31-TC4 LMC are about twice than that of the as-received AZ31 foil,and the specific strength is 38.8%higher than that of AZ31 alloy.Furthermore,the bending strength and fracture toughness of AZ31-TC4 LMC are increased by 33%and 129.9%,respectively.The extremely narrow intermetallics layer around the TC4/AZ31 interface has not undergone severe delamination during the mechanical tests.Therefore,the mechanical properties of the composite are significantly improved through the load transfer effect.In order to elucidate the hybrid-reinforced and damping mechanisms of the（NiTi_f/AZ31）-TC4 LMC,the interfacial microstructure,damping,tensile,compression,bending and fracture toughness tests were carried out.SEM observation shows that the microstructure of（NiTi_f/AZ31）-TC4 LMC is compact without obvious macroscopic defect,and the fiber arrangement is uniform.（NiTi_f/AZ31）-TC4 LMC shows an internal friction peak when the test temperature rises to 65℃.Compared with the AZ31 alloy and AZ31-TC4 LMC at the same temperature,the damping factors are increased by 221.9%and 96.2%,respectively.The enhancement of damping property is attributed to the phase transformation in NiTi alloy.The quasi-static and dynamic compressive properties of（NiTi_f/AZ31）-TC4LMC are almost the same as those of AZ31-TC4 LMC.The tensile strength of（NiTi_f/AZ31）-TC4 LMC is increased by 112.7%and 4.4%compared with the as-received AZ31 foil and AZ31-TC4 LMC,respectively.For the failure strain,these values are 4.2%and44.7%.In addition,compared with the as-received AZ31 foil,the specific strength of the（NiTi_f/AZ31）-TC4 LMC is increased by 33.3%.The bending strength of（NiTi_f/AZ31）-TC4LMC is 36.4%and 81.2%higher than that of AZ31-TC4 LMC and AZ31 alloy,respectively.Among the various as-fabricated composites,the（NiTi_f/AZ31）-TC4 LMC obtains the best fracture toughness,which is 165.7%,130.4%and 15.6%higher than that of AZ31 alloy,SMAFR-AZ31 composite and AZ31-TC4 LMC,respectively.Based on the hybrid-reinforced mechanism,the high-performance fiber and foil reinforcements can effectively improve the comprehensive properties of the composite through load transfer effect of the interface.更多还原