新一代镍基变形高温合金GH4065A的组织控制与力学性能

由于GH4065A合金的强化相γ′相的体积分数为43.0%,显微组织演化规律不同于传统的变形高温合金与粉末高温合金。系统分析了GH4065A合金的锻态组织特点与演化机制,发现其显微组织是一种不完全的动态再结晶(DRX)组织,动态再结晶晶粒被大尺寸γ′相限制长大,同时这些γ′相因晶界短路扩散而粗化,而未动态再结晶(unDRX)晶粒内弥散分布的小尺寸γ′相阻碍位错运动,进而形成大量由位错胞壁构成的亚结构。基于合金的锻态组织特点,可以通过固溶处理,利用动态回复(DRV)机制基本消除残留的未动态再结晶组织。根据GH4065A合金γ′相的固溶温度,可将热处理制度分为亚固溶处理与过固溶处理2种,亚固溶处理后的晶粒度为8.0级,过固溶处理的晶粒度为4.0级。经亚固溶处理后,GH4065A合金涡轮盘锻件的力学性能达到了第2代粉末涡轮盘的水平。

Microstructure control and mechanical properties of the newest nickel-based wrought superalloy GH4065A

Because the volume fraction of strengthening phase ?á? is high (43. 0%), the microstructure evolution law of GH4065A is quite different from traditional wrought superalloy and powder superalloy. The character and evolution mechanism of microstructure of forged disk made of GH4065A alloy were analyzed. The results show that the microstructure of the alloy is incomplete DRX microstructure, and the growth of DRX grains is limited by large ?á? phase which coarsens for the short circuit diffusion at grain boundary, while lots of sub-structure form by dislocation cells in unDRX grains for dislocations are fixed by small ?á? phase in unDRX grains. Based on the characteristics of forged microstructure, the unDRX grains can be eliminated by DRV during solution treatment. According to the solution temperature of ?á? phase of GH4065A alloy, heat treatment can be divided into supersolvus solution and subsolvus solution. After subsolvus solution and supersolvus solution, the grain sizes are 8. 0 and 4. 0 respectively. After subsolvus treatment, the mechanical properties of the forged disk made of GH4065A reach the level of the second generation powder metallurgy nickel-based disk.