热处理对网状结构TiBw/TA15(Mo,Si)复合材料组织与性能的影响

采用低能球磨结合热压烧结的方法设计制备网状结构3.4%(体积分数)TiBw/TA15(Mo,Si)钛基复合材料,对复合材料进行不同热处理,研究热处理对其组织与性能的影响。通过X射线和透射电镜表征复合材料物相变化,结合扫描电镜对材料组织变化进行分析,结果表明:添加的TiB2原位生成TiB晶须(TiBw)增强相分布在TA15钛合金颗粒周围形成网状结构,MoSi2以固溶析出形式形成(Ti,Zr)5Si3细小增强相和Mo固溶原子分布在网状结构内部;1200℃固溶处理未改变TiBw组织形貌以及复合材料网状结构特征,基体组织转变为马氏体α’,(Ti,Zr)5Si3增强相重新过饱和固溶;550~700℃时效处理后基体马氏体组织发生分解,过饱和硅元素在α/β界面和网状界面析出,随时效温度提高,针状马氏体α’逐渐转变为片层状(α+β)相,析出的硅化物数量逐渐变多尺寸变大。利用Instron-5569型万能试验机对复合材料力学性能进行测试分析,结果表明:随时效温度升高复合材料强度先升高后降低,塑性变化趋势与强度变化相反;1200℃/45 min固溶处理TiBw/TA15(Mo,Si)复合材料压缩强度为1751MPa,断裂应变为6.7%,经过1200℃/45 min固溶+600℃/90 min时效处理后复合材料压缩强度达到1900 MPa,断裂应变下降至3.6%。

Effects of heat treatment on microstructure and mechanical properties of TiBw/TA15(Mo,Si)composites with network microstructure

The experimentation adopted low energy ball milling combining,with hot pressing sintering,to design and fabricate 3.4%(volume fraction)TiBw/TA15(Mo,Si)titanium matrix composites,for investigating the effects of heat treatment on the composites’microstructure and mechanical properties.Through phase analysis about the composites via X-ray and transmission electron microscopy(TEM),while also analyzing the composites’microstructure via scanning electron microscope,Several results the experimentation has observed.Firstly,the added TiB2 generated in-situ synthesized TiBw reinforcement which was distributed around the TA15 titanium alloy powder and formed a network microstructure.Moreover,fine(Ti,Zr)5Si3 reinforcement was formed by solid solution and precipitation mechanism and then Mo element was solid solution inβphase after MoSi2 solution at high temperature.Secondly,solution treatment with 1200℃did not change the microstructure of TiBw neither the characteristics of the network microstructure of the composites,and the matrix was turned into martensiteα'.(Ti,Zr)5Si3 reinforcement was re-dissolved and transformed to supersaturated solid solution.Thirdly,after aging treatment at 550-700℃,the martensitic matrix was decomposed,and the supersaturated silicon element was precipitated at the interface of bothα/βinterface and the network boundary.The acicular martensiteα'was gradually transformed into lamellar(α+β)phase,and the amount of silicide precipitates was gradually increased with the increase of aging temperatures.Later,the experimentation further utilized Instron-5569 universal testing machine to test and analyze the composites’mechanical properties.The experimental results show that the strength of titanium matrix composites is increased first and then decreased with the increase of aging temperature instead,and the plastic change is opposite to the strength change.The compressive strength of TiBw/TA15(Mo,Si)composites at 1200℃/45 min solution treatment is 1751 MPa,and the strain at break is 6.7%.After 1200℃/45 min solution treatment+600℃/90 min aging treatment,the compressive strength of the composites reaches 1900 MPa and the strain at break decreases to 3.6%.