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首页> 美国卫生研究院文献>Materials >Effect of Thermal Cycle on Microstructure Evolution and Mechanical Properties of Selective Laser Melted Low-Alloy Steel
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Effect of Thermal Cycle on Microstructure Evolution and Mechanical Properties of Selective Laser Melted Low-Alloy Steel

机译：热循环对选择性激光熔炼低合金钢组织演变和力学性能的影响

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摘要

Low-alloy steel samples were successfully fabricated by selective laser melting (SLM). The evolution of the microstructure and the mechanical properties were investigated with different values of the energy area density (EAD). The results revealed that the initial solidification microstructures of the single tracks with different EADs were all martensite. However, the microstructures of bulk samples under different EADs were not martensite and differed significantly even from one another. When EAD increased from 47 to 142 J/mm , the mixed lower bainite and martensite austenite microstructure changed to granular bainite; further, the morphology of bainite ferrite gradually changed from lath to multilateral. Moreover, with the increase of EAD, the grain size was remarkably reduced because of the increasing austenitizing periods and temperature during thermal cycling. The average grain size was 1.56 µm, 3.98 µm, and 6.31 µm with EADs of 142 J/mm , 71 J/mm , and 47 J/mm , respectively. Yield strength and tensile strength of the SLM low-alloy steel increased with the increase in EAD; these values were significantly more than those of the alloys prepared by traditional methods. The microstructure of the SLM low-alloy steel samples is not uniform, and the inhomogeneity becomes more significant as EAD decreases. Simultaneously, when EAD decreases, the fracture mechanism changes from ductile to a mixture of ductile and brittle fracture; this is in contrast to the samples prepared by traditional methods. This study also found a stress concentration mechanism around large pores during plastic deformation that resulted in a brittle fracture. This indicates that large-sized pores significantly degrade the mechanical properties of the specimens.
机译：通过选择性激光熔化（SLM）成功制造了低合金钢样品。用不同的能量面积密度（EAD）值研究了组织的演变和力学性能。结果表明，具有不同EAD的单道的初始凝固组织均为马氏体。然而，在不同的EADs下，大块样品的微观结构不是马氏体，甚至彼此之间也存在显着差异。当EAD从47 J / mm增加到142 J / mm时，混合的下贝氏体和马氏体奥氏体的显微组织变为粒状贝氏体。另外，贝氏体铁素体的形态从板条逐渐变为多边。此外，随着EAD的增加，由于热循环中奥氏体化时间和温度的增加，晶粒尺寸显着减小。平均晶粒尺寸为1.56 µm，3.98 µm和6.31 µm，EAD分别为142 J / mm，71 J / mm和47 J / mm。 SLM低合金钢的屈服强度和抗拉强度随着EAD的增加而增加；这些值明显高于通过传统方法制备的合金。 SLM低合金钢样品的微观结构不均匀，并且随着EAD的降低，不均匀性变得更加明显。同时，当EAD减小时，断裂机理从延性断裂转变为延性断裂和脆性断裂的混合体。这与通过传统方法制备的样品相反。这项研究还发现在塑性变形过程中大孔周围的应力集中机制会导致脆性断裂。这表明大孔会大大降低样品的机械性能。

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