Abstract
Hot deformation behavior of Al–0.2Sc–0.04Zr (wt.%) aluminum alloy was investigated via conducting hot compression tests at temperatures of 440–600 °C and at strain rates, ranging from 0.001 to 5 s−1, at an interval of an order of magnitude. The characteristics of the true stress–strains acquired in the hot compression tests were investigated, and the influence of processing parameters on the microstructure of the deformed samples was observed by using optical microscope and electron back-scattered diffraction (EBSD). Two types of processing maps for Al–0.2Sc–0.04Zr alloy were developed using the Kumar–Prasad (K–P) and Murty–Rao (M–R) instability/stability criteria, respectively. The prediction results of two types of processing maps were examined. Based on the analysis of the M–R processing map and EBSD, a deformation mechanism map covering a wide range of temperature and strain rate was developed. The result shows that the flow stress had a rapid increase to the maximum stress, and subsequently, the flow stress decreases continually to be of steady-state type when the deformation continues on. The M–R criterion can more accurately predict the unstable region than the K–P criterion. The optimum temperature T and strain rate dot{varepsilon } combination conditions for Al–0.2Sc–0.04Zr alloy are T = 520–560 °C, dot{varepsilon } = 10−3 s−1 or dot{varepsilon } = 0.1–5 s−1. The microstructure evolution dominated by the predominant or complete dynamic recrystallization can be acquired by deformation at the combination conditions. However, it is dominated mainly by dynamic recovery at lower temperatures (T < 520 °C) and by dynamic recrystallization at higher temperatures (T > 520 °C). In addition, the microstructure of specimen deformed at 600 °C shows a growing and coarse trend. Moreover, the nano-dimension precipitate particles of Al3(Sc,Zr) are uniformly distributed throughout Al matrix. The efficiency parameter η value of Al–0.2Sc–0.04Zr alloy in processing maps is smaller in comparison with that in pure aluminum, and it could be attributed to these nano-dimension particles.
Highlights
Due to its superior mechanical properties, thermal stability, high-temperature conductivity, corrosion resistance and creep resistance, the Al–0.2Sc–0.04Zr alloy has become a popular candidate material for the development of new super-heat-resistant wires [1, 2]
We developed two types of processing maps for Al–0.2Sc–0.04Zr from the flow curves measured during hot compression over wide ranges of forming temperature and strain rate using two common instability/stability criteria, the Kumar– Prasad (K–P) and Murty–Rao (M–R) criteria
The flow stress–strain curves can be divided into two types: dynamic recovery (DRV) and DRX [15],in accordance with the dynamic softening mechanisms that occur during hot deformation
Summary
Due to its superior mechanical properties, thermal stability, high-temperature conductivity, corrosion resistance and creep resistance, the Al–0.2Sc–0.04Zr alloy has become a popular candidate material for the development of new super-heat-resistant wires [1, 2]. Researches show that, after cold working deformation and aging treatment, the strength of the Al– 0.2Sc–0.04Zr alloy improves significantly to more than 200 MPa [3, 4]. Since Al–0.2Sc–0.04Zr has tremendous commercial potential for highstrength, super-heat-resistant wire for aerial materials, its high-temperature flow behavior under various processing conditions should be investigated thoroughly to achieve optimal performance control
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