热轧对N08120镍基高温合金微观组织与力学性能的影响

Effect of Hot Rolling on Microstructure and Mechanical Properties of N08120 Ni-Based Superalloy

摘要:

研究了N08120高温合金在780 ℃和单道次变形量为10%的热轧过程中，通过累计变形获得40%、60%、80%变形量试样的微观组织演变和力学性能。结果表明，变形过程中，晶界及晶内均有MC和M₂₃C₆碳化物析出，这些弥散分布的碳化物能够有效阻碍位错运动，提升材料强度。动态回复是热轧过程中的主要软化机制，位错通过滑移和重组逐步形成位错胞结构。由于晶界对位错的强烈阻碍作用及较高的界面能，位错优先在晶界处聚集，进而诱发局部再结晶，形成细小的再结晶晶粒。随着变形量增大，合金织构由Rotated Goss {110}<110>逐渐转变为Rotated Cube {110}<112>，并最终演化为Copper {112}<111>类型。在40%变形量下，加工硬化效应显著，屈服强度由322 MPa提升至867 MPa，硬度由196 HV_0.5增至337 HV_0.5；当变形量超过40%后，材料的屈服强度与硬度趋于稳定。这主要归因于热轧过程中的N08120高温合金的碳化物、位错密度、亚结构以及再结晶演变。

Abstract:

The microstructure evolution and mechanical properties of the N08120 superalloy rolled at 780 ℃ and deformed through the cumulative reduction of 40%, 60%, and 80% with the single pass reduction of 10% were investigated. The experimental results show that MC and M₂₃C₆ carbides precipitate at grain boundaries and within the grains during deformation. These finely dispersed carbides effectively hinder dislocation motion, thereby enhancing the strength of the material. Dynamic recovery is identified as the predominant softening mechanism during hot rolling, where dislocations progressively reorganize into dislocation cell structures through slip and recombination. Owing to the strong pinning effect of grain boundaries on dislocations and their high interfacial energy, dislocations preferentially accumulate near grain boundaries, inducing localized recrystallization and the formation of fine recrystallized grains. With increasing deformation amount, the alloy texture transitions progressively from Rotated Goss {110}<110> to Rotated Cube {110}<112> and finally to the Copper {112}<111> type. After 40% deformation, work hardening is significant, with the yield strength increasing from 322 MPa to 867 MPa and the microhardness rising from 196 HV_0.5 to 337 HV_0.5. Beyond 40% deformation, both yield strength and microhardness tend to stabilize. This is mainly attributed to the evolution of carbides, dislocation density, substructure, and recrystallization in N08120 superalloy during hot rolling.