不同预热温度下电子束粉末床熔融GH3536组织演变与力学性能研究

Study on Microstructural Evolution and Mechanical Properties of Electron Beam Powder Bed Fusion GH3536 at Different Preheating Temperatures

摘要: 本文探究了电子束粉末床熔融工艺中预热温度对GH3536合金显微组织与力学性能的影响机制，选择了850℃和1000℃两种预热条件。结果显示，较低的预热温度容易在增材过程中产生较高的热梯度和较快的冷却速率，导致形成更细小的蜂窝亚颗粒和更高的错位密度。力学性能表明，850℃预热样品展现出更高的屈服强度(293.4 MPa)和抗拉强度(564.8 MPa)，以及更高的显微硬度(205.6 HV)，这主要归因于细化的晶粒结构、较高的位错密度及细小碳化物的复合强化作用。相比之下，1000℃预热样品虽强度较低(屈服强度275.4 MPa，抗拉强度517.8 MPa)，但表现出更优异的塑性，断口表面发现大量相互连接的韧窝特征，这主要归因于高温预热促进了碳化物的粗化与元素再分布，削弱了强化效果但改善了塑性；同时σ相的析出导致基体软化、应力集中和晶界脆化。本研究阐明了预热温度–微观组织–力学性能之间的内在关联，为GH3536合金构件的EB-PBF工艺优化提供了理论依据。

Abstract: This study investigates the influence mechanism of preheating temperature on the microstructure and mechanical properties of GH3536 alloy in the electron beam powder bed fusion process, selecting two preheating conditions: 850˚C and 1000˚C. Results indicate that lower preheating temperatures tend to generate higher thermal gradients and faster cooling rates during the additive process, leading to the formation of finer honeycomb subgrains and higher dislocation density. Mechanical testing revealed that the 850˚C preheated specimens exhibited higher yield strength (293.4 MPa) and tensile strength (564.8 MPa), along with increased microhardness (205.6 HV). This performance improvement is primarily attributed to the refined grain structure, elevated dislocation density, and composite strengthening effect of fine carbides. In contrast, the 1000˚C preheated specimens exhibited lower strength (yield strength 275.4 MPa, tensile strength 517.8 MPa) but superior ductility, with fracture surfaces displaying numerous interconnected ductile dimples. This was primarily attributed to high-temperature preheating promoting carbide coarsening and element redistribution, which weakened strengthening effects but improved ductility; simultaneously, σ-phase precipitation led to matrix softening, stress concentration, and grain boundary embrittlement. This study elucidates the intrinsic relationship between preheating temperature, microstructure, and mechanical properties, providing a theoretical basis for optimizing the EB-PBF process for GH3536 alloy components.