复合制造TC4钛合金组织与拉伸性能

Microstructure and Tensile Properties of Hybrid Manufacturing TC4 Titanium Alloy

锻造与激光选区熔化相结合的复合制造技术为复杂整体钛合金构件制造提供了高效率、低成本技术新途径,掌握复合制造钛合金的组织和性能调控方法对于实现该技术工程应用至关重要。通过金相及扫描表征、室温拉伸测试和断口分析,对比研究了单层层厚分别为30μm和60μm的两种选区激光熔化典型工艺参数的复合制造TC4钛合金结合区显微组织和室温拉伸性能。结果表明,单层层厚对复合制造TC4钛合金结合区的显微组织和室温拉伸性能无明显影响,选择大的层厚可显著提高成形效率。复合制造TC4结合区由增材区的马氏体组织和基体区的等轴组织构成梯度组织,无明显热影响区,增材区的显微硬度略高于锻件基体区。复合制造TC4钛合金增材区、基体区和结合区的室温拉伸性能均达到锻件标准要求,结合区抗拉强度介于增材区和基体区之间,而断后伸长率与增材区相当。由于增材区和基体区的拉伸强度和塑性差异,试验提出在室温拉伸过程中梯度组织结合区界面会产生切应力以协调变形的推论,结合区拉伸断口上增材和基体区分别呈现准解理和韧窝形貌。

The hybrid manufacturing technique combining forging and selective laser melting techniques provides an effective approach for the manufacturing of complex integral titanium alloy component with high efficiency and low cost.The microstructure and properties controlling method of hybrid manufacturing titanium alloys is very important for the engineering application.The microstructure and mechanical properties of hybrid manufacturing TC4 samples of two typical process parameters with the layer thickness of 30μm and 60μm of selective laser melting were studied by means of metallographic and microscopic observation,room tensile testing and fractography observation.The results showed that the layer thickness has no effect on the microstructure and properties,however,larger layer thickness can increase the forming efficiency.The gradient microstructure in the bond zone of hybrid manufacturing TC4 is consist of the martensite structure in additive zone and equiaxed structure in substrate zone.There is no obvious heat affected zone in the forging substrate.The micro hardness of additive manufacturing zone is higher than that in the forging zone.The tensile properties of hybrid manufacturing TC4 can satisfy the requirement of the forging standard.The tensile strength of the bond zone is between the additive manufacturing zone and forging zone,but the elongation is equal to the additive manufacturing zone.Due to their different strength and ductility,it is concluded that a shear stress in the interface of gradient microstructure bond zone would form to adjust the deformation in this research.The fractography of the bonding zone tensile specimen is consist of quasi cleavage morphology in the additive manufacturing half zone and dimple morphology in the forging half zone.