Abstract
In this paper, the dynamic mechanical properties of GH4720Li nickel-base alloy under a large temperature range and high and low strain rates were studied by the hot compression test. The difference of mechanical properties of GH4720Li alloy under high and low strain rates was analyzed from the perspective of microstructure. The hot compression test experimental results showed that the true stress of GH4720Li alloy decreased at a low strain rate as the trial temperature elevated. Nevertheless, it was abnormal that the true stress increased at high strain rate condition as temperature elevated. By comparing the microstructure under high and low strain rates, it was found that the precipitates under low strain conditions contained a large amount of Cr (Mo). However, the content of Cr (Mo) in the precipitates at a high strain rate decreased, while the content of Fe increased. It would be concluded that Cr (Mo) would reduce the compressive strength and plasticity of GH4720Li alloy, while Fe would increase the compressive strength and plasticity of GH4720Li alloy. In addition, under the condition of a low strain rate, the shape of Cr (Mo) precipitates obtained at 20°C was lamellar, but it was spherical at 800°C. The compressive strength of GH4720Li composites with lamellar precipitates was higher than that of spherical precipitates.
Highlights
GH4720Li was a kind of advanced high-strength wrought Nimatrix superalloy, which was developed for application in high-integrity rotating components of gas turbine engines such as discs and turbine blades [1,2,3]
The hot compression tests were conducted over a wide range of temperature (20~1000°C) and strain rate (10~5000 s-1) to obtain further understandings of the deformation behavior of GH4720Li alloy
It was found that the mechanical properties of GH4720Li alloy showed different trends under high and low strain rates
Summary
GH4720Li was a kind of advanced high-strength wrought Nimatrix superalloy, which was developed for application in high-integrity rotating components of gas turbine engines such as discs and turbine blades [1,2,3]. Wan et al had investigated the high-temperature deformation behavior of an U720ULi alloy by the hot compression test at a temperature of 1060°C~1080°C and strain rates of 0.001~10 s-1. It demonstrated that high activation energy for γ + γ′ dual-phase microstructures was mainly attributed to the precipitation hardening effect of γ′ (Ni3 (Al, Ti)) particles [4]. There were few reports on the high strain rate dynamic mechanical properties of GH4720Li alloy at a wide range of temperatures. The high strain rate mechanical properties of GH4720Li alloy were investigated under a wide range of temperature changes. The differentiation of mechanical properties between high strain rate and low strain rate was explained in detail
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