【作者】 王博；

【导师】 耿林；

【作者基本信息】 哈尔滨工业大学 ， 材料学， 2011， 硕士

【摘要】 本文以平均粒径为110μm的Ti6Al4V粉末和5μm的TiB2颗粒做为原材料,采用反应热压法制备了TiB晶须(TiBw)增强钛基复合材料,增强体呈准连续网状分布,体积分数分别为5%和8%。对复合材料进行热挤压变形,并研究挤压比对复合材料组织与性能影响。对挤压后的复合材料进行热处理研究。采用SEM,OM等方法对TiBw/Ti6Al4V复合材料的显微组织进行观察。测试了室温及高温拉伸性能并对结果进行了分析。微观组织分析表明,烧结态复合材料中的TiB为棒状或空心管状晶须,分布在原始球形Ti6Al4V颗粒周围,形成准连续网状结构。烧结态复合材料经挤压变形后,网状结构破坏,TiB晶须沿挤压方向分布,同时基体晶粒被拉长。对5vol.%TiBw/Ti6Al4V选取挤压比9:1和16:1进行热挤压研究。从纵截面观察,复合材料在挤压比为16:1时晶须分布更为均匀,且更小横截面晶须所围尺寸更小晶须分布更加离散,说明随着挤压比的提高复合材料局部体积分数降低。对于8vol.%TiBw/Ti6Al4V烧结态和挤压态复合材料,晶须在原始晶粒周围有局部偏聚现象。对挤压态复合材料选取固溶时效热处理,并研究了固溶温度和时效温度对复合材料组织与性能的影响。结果表明复合材料经淬火处理后得到条状初生相和马氏体,并随着固溶温度的提高基体组织中初生相含量降低,经时效处理后马氏体分解为细小弥散和β混合组织,随着时效温度提高,马氏体分解产物尺寸增大,初生相尺寸增加。体积分数5%和8%烧结态复合材料抗拉强度达到1030MPa和1232MPa。较采用相同工艺Ti6Al4V合金提高7.2%和27%。其延伸率为3.2%和1.3%。在1100℃选取挤压比16:1进行热挤压变形后,复合材料的强度和塑性都有较大程度提高。体积分数5%和8%挤压态复合材料抗拉强度分别为1206MPa与1311MPa,较烧结态分别提高17.1%和6.5%。延伸率分别为12%与4.8%,较烧结态分别提高275%和269%。对于体积分数5%和8%的复合材料在990℃淬火600℃时效6个小时复合材料具有较好的室温综合力学性能,其室温抗拉强度为1364MPa和1469MPa,延伸率达到7.8%和2.5%。通过测试400℃、500℃、600℃和700℃两种体系TiBw/Ti6Al4V热处理态复合材料的高温性能发现。在600℃以下复合材料的具有较高的拉伸性能,并且随着测试温度提高强化效果减弱。其中5vol.%和8vol.%的复合材料在400℃抗拉强度达到1158MPa和1042MPa,在700℃抗拉强度分别为211MPa和224MPa。更多还原

【Abstract】 TiBw/Ti6Al4V composites with a uniform network microstructure were fabricated by in situ reactive hot processing by the system of Ti6Al4V and TiB2 powers.The average size of the original Ti6Al4V and TiBw powders were 110μm and 5μm respectively. The effects of hot extrusion and heat-treatment on microstructure and properties of composites were studied. The microstructures of the composites were studied with SEM and optical microscope. The tensile properties of composites at both room and high temperatures were measured.Microstructure analysis results showed that TiB is rodlike whisker,which distributed around the boundaries of Ti6Al4V matrix particles as-received. The TiB whisker subsequently formed into network structure.After extrusion microstructure analysis results showed that the network structure were damaged.TiB whiskers were broken and rotated distributing along the extrusion direction and local volume fraction of TiB whiskers were decreased. It can be seen in longitudinal section the distribution of TiB whiskers in extruded composites with the extrusion ratio 16:1 were more discrete than the extrusion ratio 9:1,which guaranteed connectivity of matrix alloy. The effects of heat treatment solution temperature and aging temperature on microstructure and mechanical properties of extruded composites were investigated.The results show that with increase of solution temperature primary volume fraction decreases. With the aging temperature increased,the martensite decomposition product size increases,at the same time strip phase grows integration.The room temperature tensile strength of 5vol.%TiBw/Ti6Al4V sintered composites was 1030MPa and the elongation of composites was 3.2%.As 8vol.% TiBw/Ti6Al4V sintered composites,tensile strength was 1232MPa and the elongation was 1.3%. After the composites extruded at 1100℃,compared to sintered composites,the tensile strength and especially their elongationt were greatly improved. Tensile strength of 5vol.% and 8vol.% extruded composites were 1206MPa and 1311MPa,compared with sintered 17.1% and 6.5%.The elongation were 12% and 4.8% respectively,compared with sintered composites were increased by 275% and 269%. The strength and ductility of extruded composites were improved with the increase of extrusion ratio. 5vol.% of composite quenched at 990℃aging at 600℃have better mechanical properties,its tensile strength is 1364MPa,elongation 7.8%. The 8vol.% of composite with the same heat treatment tensile strength was 1469MPa,elongation was 2.5%.The high temperature tensile results show that with the the increase of testing temperature strengthening effect is weakened.At 400℃,tensile strength of 5vol.% and 8vol.% composites after heat treatment were 1042Mpa and 1158MPa.At 700℃,5% and 8vol.% composites have considerable strength,which were 215Mpa and 223Mpa respectively.更多还原