Abstract
Among newly developed TX (Mg-Sn-Ca) alloys, TX32 alloy strikes a good balance between ductility, corrosion, and creep properties. This study reports the influence of aluminum and zinc additions (0.4 wt % each) to TX32 alloy on its strength and deformation behavior. Uniaxial compression tests were performed under various strain rates and temperature conditions in the ranges of 0.0003–10 s−1 and 300–500 °C, respectively. A processing map was developed for TXAZ3200 alloy, and it exhibits three domains that enable good hot workability in the ranges (1) 300–340 °C/0.0003–0.001 s−1; (2) 400–480 °C/0.01–1 s−1; and (3) 350–500 °C/0.0003–0.01 s−1. The occurrence of dynamic recrystallization in these domains was confirmed from the microstructural observations. The estimated apparent activation energy in Domains 2 and 3 (219 and 245 kJ/mole) is higher than the value of self-diffusion in magnesium. This is due to the formation of intermetallic phases in the matrix that generates back stress. The strength of TXAZ3200 alloy improved up to 150 °C as compared to TX32 alloy, suggesting solid solution strengthening due to Al and Zn. Also, the hot deformation behavior of TXAZ3200 alloy was compared in the form of processing maps with TX32, TX32-0.4Al, TX32-0.4Zn, and TX32-1Al-1Zn alloys.
Highlights
Owing to their light weight and specific stiffness, Mg alloys are being developed for use as structural parts in the automobile and aerospace industries [1]
The optical microstructures observed on the deformed specimens compressed at 300 ◦ C/0.0003 s−1 and 350 ◦ C/0.0003 s−1 are presented in Figure 9a,b, respectively
These reveal the initiation of fine recrystallized necklace type grain structure in the matrix, suggesting that the dynamic recrystallization (DRX) mechanism occurs in this window (Domain 1)
Summary
Owing to their light weight and specific stiffness, Mg alloys are being developed for use as structural parts in the automobile and aerospace industries [1]. It is essential to develop a technology to optimize the hot working of Mg-3Sn-2Ca-0.4Al-0.4Zn (TXAZ3200) alloy to ensure reliability via the formation of defect-free microstructures The aim of this investigation is to evaluate the strength of TXAZ3200 alloy under compression as well as to generate a processing map to identify the best deformation conditions that can yield optimum hot workability. The dynamic materials model formed the basis in developing processing maps for a number of materials, using the concepts and procedures that have been well established [13,14] In this approach, two different maps, namely, a power dissipation efficiency (η) map and an instability (ξ) map, are first determined over a range of temperature and strain rate at a chosen deformation strain, and superimposed to generate a processing map. The map helps to avoid the conditions of flow instability
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