概述了近10年来我国变形高温合金的研制情况。介绍了航空发动机用涡轮盘材料718Plus,GH4720Li,GH4065合金的特点,燃烧室用GH3230合金以及燃气轮机用GH4706合金的研制进展。并对变形高温合金热加工新技术进行了总结,包括针对易偏析材料开发的ERS-CDS新工艺,改善变形高温合金棒材组织的反复镦拔工艺,提升高性能难变形高温合金热塑性的缓冷处理和热机械循环处理技术。最后,展望了我国变形高温合金产业的未来。

The Portevin-Le Chatelier (PLC) effect is a plastic instability in alloys at certain strain rates and deformation temperatures. This plastic instability exhibits serrated yielding in the temporal domain and strain localization in the spatial domain. Wrought Ni-based superalloys often exhibit the PLC effect. To guarantee the safe and stable operation of equipment, it is important to study the PLC effect in wrought Ni-based superalloys. This paper provides a review of various experimental phenomena and micromechanisms related to the PLC effect in wrought Ni-based superalloys, which have been reported in various publications in recent years and include work from our own group. The influences of stacking fault energy and γ′ precipitates on the PLC effect in wrought Ni-based superalloys are also discussed in detail. Additionally, several suggestions for the future study of the PLC effect in wrought Ni-based superalloys are provided.

GH4151 is a heavy alloy, hard-to-deform Ni-based superalloy with service temperatures reaching up to 750-800 oC. It is an important candidate material for high-temperature alloys used in the turbine disks of the new-generation advanced aeroengines. During service, the rapid superposition of temperature and stress makes turbine disks susceptible to damage. This study explores the use of hard-to-deform GH4151 alloy used for turbine disks. The tensile behavior of the GH4151 alloy within a temperature range of 23-950 oC was investigated using advanced techniques such as SEM, TEM, EDS, and EPMA. The microstructural changes, deformation microstructure, and their impact on the fracture mechanism were analyzed, and the fracture failure mechanisms of the alloy at various temperatures were elucidated. The results indicate that yield strength and tensile strength initially decrease gradually, followed by a rapid decline with increase in experimental temperature. Meanwhile, elongation after fracture of the alloy decreased initially and increased with increasing experimental temperature. The fracture mode transitioned from a mixed fracture to an intergranular fracture. Further research showed that during tensile testing at temperatures of 23-550 oC, deformation primarily occurred in the γ channels, with a significant accumulation of dislocations at the γ/γ′ interfaces. This led to the tearing of the γ/γ′ interfaces and the formation of microvoids, which in turn generated a transgranular fracture. The intergranular fracture within the mixed-fracture mode is attributed to the stress concentration at MC carbide interfaces, resulting in the formation of voids. During tensile testing at temperatures of 650-800 oC, cracks were initiated via an intergranular fracture, and propagated through mixed-fracture modes. Deformation occurred simultaneously in the γ channels and the γ′ phase. Dislocation pile-up at the grain boundaries accelerated the enrichment of O atoms toward the elastic stress fields or the enrichment of defects at the grain boundaries under high-temperature and high-stress conditions. Such enrichment led to dynamic embrittlement of the grain boundaries, causing intergranular fracture, which reduced the elongation after fracture. As the strain increased, crack propagation was accelerated, reducing the time available for the O atoms to dynamically embrittle the grain boundaries. When the accumulation of dislocations at the γ/γ′ interfaces reached a critical value, crack propagation shifted to a mixed-fracture mode dominated by transgranular fracture. During tensile testing at 950 oC, cracks were initiated and propagated via intergranular fracture. The morphology of the γ′ phase changed to an approximately spherical shape, reducing the hindrance to dislocation motion. This reduction did not lead to the coalescence of microvoids at the γ/γ′ interfaces, and thus, no transgranular fracture occurred in the samples tested at 950 oC. Because of the decrease in tensile strength at 950 oC, the external stress applied was reduced, and crack propagation slowed down, elongation was increased.

为探明服役过程中温度和应力快速叠加造成的涡轮盘损伤，本工作以涡轮盘用难变形GH4151合金为例，采用SEM、TEM、EDS和EPMA等表征手段，研究了不同温度下GH4151合金的拉伸行为和显微组织演化规律，分析了拉伸断裂失效机制。结果表明，随实验温度升高，GH4151合金的塑性呈现出先减小后增大的趋势，断裂方式由混合断裂逐渐向沿晶断裂转变。共格γ/γ′界面和MC界面位错塞积是导致混合断裂产生的主要原因，晶界位错塞积加速了高温高应力下O原子向晶界弹性应力场或缺陷处的富集，导致晶界动态脆化，引起沿晶断裂，造成GH4151合金在650~800 ℃高温拉伸时塑性下降。950 ℃拉伸时，GH4151合金强度迅速下降，裂纹以较慢的速率扩展，导致塑性增加。

Designing high-performance aeroengine is important for development in the aviation industry. One of the key components is turbine disk material that can operate at 800oC. Among various methods for strengthening alloys, increasing the alloying degree is important, and GH4151 is one of the typical alloys with a high alloying degree. It comprises a large number of refractory metal elements and γ'-forming elements. OM, SEM, and JMatPro software were used to study the sensitivity of GH4151 microstructure evolution during heat treatment processes. The results show that a high alloying degree produces a complex microstructure with low-melting phases, such as Laves, γ/γ′ eutectic, and η phases. Due to the difference in incipient melting temperature of each precipitated phase, a three-stage heat treatment was developed to effectively eliminate the harmful phases in the alloy. The contents of segregation elements Nb and Ti in the as-cast GH4151 alloy have an obvious influence on the incipient melting temperature, whereas the effect of Mo content is relatively slight, and that of W content is not obvious. Decreasing Ti content while increasing Nb and Mo contents could reduce the incipient melting temperature of the η phase. Furthermore, increasing Ti and Mo contents while decreasing Nb content could reduce the incipient melting temperature of Laves phase. A large amount of γ'-forming elements contributes to the cooling rate sensitivity of γ′ phase evolution. 15oC/min is the critical value for the irregular growth of the γ' phase in the GH4151 alloy. When compared to alloys with low γ′-forming elements content, the γ′ phase in GH4151 alloy has a larger size when the cooling rate is > 15oC/min, and exhibits an irregular shape when the cooling rate is < 15oC/min. Thus, a high alloying degree contributes to the complex and sensitive microstructure evolution behavior of GH4151 alloy.

The typical superalloy GH4169 was prepared by selective laser melting (SLM), and then subjected to appropriate post-heat treatments, afterwardsits tensile properties was assessed in temperature range 25~650 oC. The microstructure evolution, tensile behavior at different temperatures were examinedby scanning electron microscopy and transmission electron microscopy, and the corresponding deformation mechanism of SLM GH4169 alloy was disscussed. The results show that the tensile curves of the of SLM GH4169 alloy are monotonic and smooth at 25 oC, 600 oC and 650 oC, but those at 450~550 oC are sawtooth-like. With the increasing test temperature, the tensile strength and yield strength of the SLM GH4169 alloy decreases from 1458 MPa to 1228 MPa and 1234 MPa to 1051 MPa respectively. The relationship between tensile strength and temperature of the SLM GH4169 is roughly linear with an error is less than 2%.The strengthening phases may obstruct the dislocation movement and plays a certain strengthening role in the temperature range 25~450 oC. While in the range 550~650 oC, slip bands may be the main deformation mode, and δ phases also has an adverse effect on tensile properties.

Uniaxial tensile testing explored the Portevin–Le Chatelier (PLC) effect in nickel‐based superalloys featuring high Mo/Cr mass ratios, focusing on the influence of variations in the initial microstructure on the deformation behavior at room and elevated temperatures. Experimental results indicated that the PLC effect was observed solely in the high‐temperature tensile curves. However, the deformation mechanisms and characteristics of the PLC effect varied with different initial microstructures. Solid solution (SS) and over‐aged (OA) samples exhibited C‐type serrations, while under‐aged (UA) and peak‐aged (PA) specimens, featuring short‐ and long‐range ordered phases, respectively, exhibited A + B type serrations in their tensile curves. Microstructural evolution from the SS to the UA, PA and OA states changed their stacking fault energy (SFE), leading to a sequential transformation in the plastic deformation mechanisms during high‐temperature tensile deformation: stacking fault (SF) → nanotwin → microtwin → SF. C‐type serrations in the SS samples were associated with high solute‐atom contents and SF formation. The PLC effects in the UA and PA samples were predominantly caused by solute atom pinning dislocations. Although precipitates and twins were not the primary drivers of the PLC effect, they impeded dislocation migration, exacerbated solute‐atom segregation and enhanced dislocation pinning, generating A + B‐shaped serrations. In the OA specimens, precipitated phases induced interfacial mismatch under thermal‐force coupling. SF shearing of the precipitated phase and subsequent re‐dissolution facilitated the formation of C‐type serrations, whose PLC effect was induced by the combined action of dynamic strain aging (DSA), SFs of the matrix and diffusion‐controlled pseudo‐locking mechanisms.