Hot Forging Behavior of Mg−8Al−4Ba−4Ca (ABaX844) Alloy and Validation of Processing Map


Newly developed die-cast alloys based on Mg–Al−Ba–Ca (ABaX) system show promise for high temperature creep resistance. ABaX844 alloy is one of them and it has limited workability due to high alloy content. To identify the optimum processing conditions, processing map for this alloy was developed earlier, which exhibited two workability domains in the temperature and strain rate ranges: (1) 340–410 °C and 0.0003–0.005 s−1, and (2) 425–500 °C and 0.0003–0.1 s−1. Dynamic recrystallization (DRX) occurs in these domains. The map also exhibited extensive flow instability mainly at strain rates > 0.01 s−1 up to a temperature of 400 °C and at strain rates >0.1 s−1 beyond 400 °C. The aim of the present study is to validate the findings of processing map by performing forging tests in the temperature range 300–500 °C (at an interval of 40 °C) and forging speeds of 0.01, 0.1, 1 and 10 mm s−1 to produce a rib-web (cup) shape component. Finite-element (FE) simulations were performed for obtaining the variations of strain and strain rate in the components during forging. The microstructures of forged specimens deformed under optimum process conditions derived from the processing map revealed the formation of dynamically recrystallized grains. The alloy specimens forged under the conditions of flow instability have fractured and/or exhibited flow localization. The results validated the predictions of the processing map and the load-stroke curves obtained by FE simulation correlated well with the experimental curves.
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