【作者】 王乐；

【导师】 张兵；

【作者基本信息】 西安建筑科技大学 ， 材料加工工程， 2016， 硕士

【摘要】 多层金属复合材料凭借其优异的综合性能以及根据实际需要存在的可设计性,已经成为当前材料科学领域研究的重点方向。本文采用退火态的纯镍N6和纯钛TA1为原材料,利用ARB技术制备Ti/Ni多层结构复合材料,研究了在ARB变形过程中复合材料的界面结合机理、组织及力学性能的演变。采用扩散热处理的方法促使复合材料发生界面扩散及反应,研究了扩散溶解层随着热处理时间、温度的生长规律,并进一步确定了扩散反应产物、扩散溶解层结构以及扩散反应对Ti/Ni多层复合材料力学性能的影响。利用光学显微镜（OM）、扫描电镜（SEM）、透射电镜（TEM）和X-射线衍射仪（XRD）研究复合材料的宏观结构、微观组织及界面相组成;采用拉伸测试及显微硬度测试研究复合材料的力学性能。结果表明,在ARB变形过程中,Ti-Ni界面均未发生明显的原子扩散,复合材料主要结合方式为机械啮合;随着ARB道次的增加,Ni层出现颈缩与断裂现象,且出现与轧制方向呈一定角度的剪切变形带;经6道次ARB变形,Ti、Ni层的晶粒尺寸得到明显细化,其中Ti层的平均晶粒尺寸为200 nm,Ni层的平均晶粒尺寸为300 nm;随着ARB道次的增加,Ti/Ni多层复合材料的抗拉强度与各层显微硬度不断增大,界面结合强度不断升高,断裂伸长率逐渐降低;经6道次ARB变形,复合材料抗拉强度升高到810 MPa,断裂伸长率为24.4%,Ti、Ni层的平均显微硬度分别为233 HV和229 HV。经不同温度、时间扩散热处理后,对比各道次界面扩散溶解层厚度,发现轧制道次对界面溶解层生长影响不大,扩散热处理温度与扩散溶解层厚度呈指数关系,温度越高形成扩散溶解层的厚度越大,扩散热处理时间与扩散溶解层厚度呈抛物线关系,时间越长形成扩散溶解层的厚度越大;复合材料界面发生扩散反应的产物分别为Ni₃Ti、TiNi、Ti₂N i,并且从Ni侧到Ti侧扩散溶解层的结构为:Ti在Ni中的固溶体–Ni₃Ti–TiNi–Ti₂N i–N i在Ti中的固溶体,扩散反应产生的金属间化合物硬度极高,而Ti、Ni侧越是靠近界面反应层,硬度值越高;随着扩散热处理温度、时间的增加,扩散反应层产生金属间化合物的厚度逐渐增加,复合材料的抗拉强度与屈服强度逐渐增大,断裂伸长率逐渐降低;在复合材料的拉伸断裂过程中,裂纹的萌生与扩展首先发生在金属间化合物Ti₂N i和N i₃Ti层,而TiNi相则具有良好的力学特性,能够有效地阻碍裂纹的进一步扩展。更多还原

【Abstract】 Multilayer metal composite material has become the focus of the current field of materials science because its excellent overall performance and the property of the design can be present.In this paper,pure nickel N6 and pure titanium TA1 as raw material was used to prepare Ti/N i multilayer composite by accumulative roll bonding.Research the bonding mechanism,microstructure and mechanical properties of Ti/N i multilayer composite.Diffusion heat treatment was used to promote interfacial diffusion and reaction of composite,research the growth rules of diffusion layer with the increase of heat treatment temperature and time,and determined the reaction product,the structure of diffusion layer,and the influences of the mechanical properties of Ti/N i multilayer composites after diffusion heat treatment.Macrostructure,microstructure and interfacial phases was studied by optical microscopy（OM）,scanning elec tron microscopy（SEM）,transmission electron microscopy（TEM）and X-ray diffraction（XRD）;The mechanical properties of composites was studied by tensile testing and hardness testing.The results showed that there is no obvious atoms diffusion in the ARB deformation process,the bonding mechanism of Ti/N i multilayer composites is mechanical engagement;With the increase of ARB passes,necking and fracture phenomena is appeared at N i layer,shear deformation zone with an angle of the rolling direction appeared in the composite.Ultrafine grains with the size of 200 nm～300 nm is acquired in both Ti and N i layer after 6 cycle;And the micro-structure homogeneity,the tensile strength,micro-hardness and interfacial bonding strength were improved with the increasing of ARB cycles.After ARB 5 cycles,the tensile strength was 810 MPa,the elongation was 24.4%,and the average micro-hardness of Ti layer and N i Layer is233 HV and 229 HV.After different diffusion heat treatment temperatures and time,compared the thickness of diffusion dissolution layer,found rolling passes has little effect of the growth rules of diffusion dissolution layer;The higher the diffusion heat treatment temperature the larger the thickness of diffusion dissolution layer,diffusion heat treatment temperature and diffusion dissolution layer thickness has a exponent relation;The longer the diffusion heat treatment time the larger the thickness of diffusion dissolution layer,diffusion heat treatment time and diffusion dissolution layer thickness has a parabolic relation.The product of interface reaction is N i₃Ti、TiNi and Ti₂N i.The intermetallic compound produced by the reaction diffusion has a very high hardness.With the increase of the diffusion heat treatment temperature and time,the thickness of intermetallic compound produced by the reaction diffusion is gradually increased,the tensile strength and yield strength of the composites is increased,and the elongation of the composites is decreased;In the Tensile fracture process of co mposite material,crack’s initiation and propagation firs occur at intermetallic compound Ti₂N i and N i₃Ti layer,however TiNi phase is having good mechanical properties,can effectively hinder crack propagation.更多还原