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为了考察激光沉积过程热行为对其微观组织的影响,采用了有限元方法对激光沉积过程进行建模,分析了多层多道激光沉积TA15钛合金试样的温度分布及内部节点的热循环特性变化,并对试样的组织进行了考察。模拟结果显示基材和沉积层上任一节点均要经历循环加热和冷却的过程,由于热量累积效应使冷却速度下降,且温度的谷值有上升的趋势。沉积试样的组织由基材的双态组织,经由热影响区,过渡到宏观组织为粗大的初生β晶粒的激光沉积区。因各沉积层经历的热循环和热历史的不同,晶内α相分别呈现针状、片层状和板条状。因冷却速度较快,α相同时在晶界处和β晶内析出,呈现网篮状魏氏体和网篮状混合集束状魏氏体形貌。主要合金元素Al、Zr、Mo、V由基体到激光沉积区均匀分布,无宏观偏析,表明沉积层组织形貌的变化跟成分偏析无关。
In order to investigate the influence of thermal behavior on the microstructure of the laser deposition process, a finite element method was used to model the laser deposition process. The temperature distribution and the thermal cycling characteristics of the internal multi-layer laser deposited TA15 titanium alloy were analyzed Changes, and the organization of the sample were investigated. The simulation results show that any node on the substrate and deposit undergo cyclic heating and cooling process, the cooling rate decreases due to the cumulative effect of heat and the trough temperature tends to increase. The microstructure of the deposited sample transitions from the bimodal microstructure of the substrate through the heat affected zone to the laser deposition zone where the macrostructure is coarse primary β grains. Due to the thermal cycles and thermal histories experienced by each sedimentary layer, the α phase in the crystal presents acicular, lamellar and lath-like, respectively. Due to the rapid cooling rate, α precipitates at the grain boundaries and in the β crystal at the same time. The main alloying elements Al, Zr, Mo, V are uniformly distributed from the matrix to the laser deposition zone without macroscopic segregation, indicating that the change of the morphology of the deposited layer has nothing to do with the composition segregation.