【作者】 张凤；

【导师】 邱贵宝；

【作者基本信息】 重庆大学 ， 工程（冶金工程）（专业学位）， 2021， 硕士

【摘要】 多孔钛基复合材料兼具着多孔金属材料与钛基复合材料的优异性能,不仅能够在保证材料综合力学性能的基础上减轻材料重量,还具有更强的韧性,耐腐蚀性以及耐高温性能,因此多孔钛基复合材料具有非常广泛的应用领域及前景。为了对多孔钛更进一步的研究,通过对其制备工艺流程进行优化,将其他具有多种优良特性的增强体与其结合成为先进功能材料或结构材料,以满足不同领域对材料的应用需求。研究颗粒增强体碳化钛和碳化硅对多孔钛基复合材料的孔隙率、孔隙结构、宏观和微观组织以及力学性能等的影响,本文实验采用粉末冶金造孔剂法,选取针状尿素作为造孔剂,在1200℃下真空烧结2h得到多孔钛基复合材料。经过一系列制备以及检测分析后得出如下结论:(1)通过球磨预处理30min后的钛粉与TiC/SiC的混合粉末,经XRD物相检测分析,发现混合物料中无新相的产生。烧结后经过处理的试样中也未发现其他物相衍射峰的出现,这表明在烧结过程中,坯样中未生成其它物质或被污染。(2)经过球磨预处理的物料所制备而成的多孔钛基复合材料,其线切割面更加光滑,组织致密。复合材料内部微观孔洞大小趋于一致,其孔隙率表现出缓慢下降的趋势,但是整体变化不大,都在原本设定的50%左右,另外未经球磨预处理组孔隙率变化没有明显规律。复合材料的横纵收缩率与孔隙率变化趋势基本一致。(3)通过金相显微镜和SEM电子显微镜观测添加了不同含量TiC颗粒增强体的多孔钛基复合材料,其结果表明,复合材料微孔小孔逐渐闭合,数量减少,宏观大孔变化不大。通过硬度测量发现,TiC增强剂的添加能够明显提高复合材料的硬度值,特别是当TiC添加量为6wt.%时,复合材料维氏硬度值达到566.74,相比较于多孔纯钛试样提高了165.32%,与此同时,多孔钛基复合材料试样初始屈服强度值也达到最大为156.45MPa,继续增加TiC,硬度值和初始屈服强度均逐渐降低。(4)在相同的制备工艺条件下,添加不同含量的SiC增强体,制备出了孔隙率介于36.02%～50.87%的多孔钛基复合材料。材料维氏硬度介于246.2～624.03,初始屈服强度为36.89～191.1MPa。添加SiC后,能够促进复合材料致密化程度的提高,孔壁上微观小孔数量的减少,烧结颈渐渐粗大而均匀,这表明SiC的添加促进了复合材料的烧结,最终促进综合力学性能的提高。通过抗压缩力学测验,多孔纯钛的断口形貌分析,其符合脆性断裂的特点,而添加了SiC的复合材料压缩断口形貌主要以塑性断裂为主并伴随局部脆性断裂,复合材料失效应力更大。更多还原

【Abstract】 Porous titanium matrix composites have the excellent properties of both porous metal materials and titanium matrix composite.They can not only reduce the weight of materials on the basis of ensuring comprehensive mechanical properties,but also have stronger toughness,corrosion resistance and high temperature resistance.As a result,porous titanium matrix composites have a very wide range of applications and prospects.For further research,the preparation process of porous titanium composites was optimized,and then the effects of TiC and SiC on the porosity,pore structure,microstructure,macrostructure and mechanical properties of porous titanium matrix composites were studied.In this experiment,metal powder metallurgy method is used,and needle-shaped urea is used as the pore former.The porous titanium matrix composites are obtained by vacuum sintering at 1200 ℃ for 2h.After a series of preparation and examination of sintered samples,the following conclusions are drawn:(1)The mixed powder of Tiand TiC/SiC powder in different proportions was pretreated by grinding for 30 minutes,and then the mixed raw material powder is refined,the surface roughness of which was also increased,and the surface activation energy became higher,which can promote sintering.After XRD analysis,no new phase was produced in the mixed material.No other phase diffraction peaks were found in the sample after sintering,which indicated that no other substances or contamination were generated in the blank during the sintering process and subsequent cutting,grinding,polishing and other processes.(2)The porous titanium matrix composites prepared by pretreatment of grinding have smoother linear cutting surface and denser tissue,and the size of microscopic pores in the composites tends to be the same.The porosity of prepared porous titanium matrix composite material showed a trend of slow decline,but the overall change was little,which was about 50% of the original setting.In addition,the porosity of the pre-treated group without grinding showed no pattern.The trend of shrinkage and porosity of the composites is basically consistent.(3)The porous titanium matrix composites with different TiC contents were observed by metallographic microscope and SEM electron microscope.Which results show that the number of micropores on the pore wall was gradually closed,and the macropores was obviously reduced,while the change of macropores is little.The sintering neck inside the material became more clear,compact and uniform.However,with the increase of TiC addition,the sintering neck becomes too coarse and the melting becomes more obvious.The micro-Vickers hardness measurement shows that the addition of TiC can significantly improve the hardness value of the composite,especially when the addition of TiC is 6wt.%,the Vickers hardness value reaches 566.74,which is 165.32%higher than that of porous pure titanium.At the same time,the compressive stress of the porous titanium matrix composites reaches the maximum of 156.45 MPa.The hardness and compressive strength of the porous titanium matrix composites decrease gradually with the increase of TiC content.(4)The porous titanium matrix composites with porosity ranging from 36.02% to50.87% were prepared by adding different contents of SiC under the same preparation conditions.The Vickers hardness of the pore wall of the composites is between246.2～624.03,and the compressive strength of which is between 36.89 ～191.1 MPa.The addition of SiC can promote the densification of the composites and the reduction of the number of microscopic pores on the pore wall,and the sintering neck was gradually thick and uniform.These phenomena indicate that the addition of SiC promoted the sintering of the composites,and finally promoted the improvement of the comprehensive mechanical properties.The fracture morphology of pure porous titanium was analyzed by compressive mechanical test,and it was found that it was in accordance with the characteristics of brittle fracture.While the characteristics of compression fracture morphology of composites with SiC added mainly belongs to plastic fracture accompanied by brittle fracture,and the failure stress of which is larger.更多还原