Connected Process Design for Hot Working of a Creep-Resistant Mg–4Al–2Ba–2Ca Alloy (ABaX422)
Abstract
:1. Introduction
2. Experimental Procedure
3. Results and Discussion
3.1. First Step: Hot Working of Cast ABaX422
3.2. Step 2: Design of Extrusion Experiment
3.3. Hot Working Behavior of ABaX422 after Extrusion
3.4. Hot Working Behavior of As-Cast Versus Extruded ABaX422 Alloy
3.5. Connected Process Design
3.6. Compressive Strength of ABaX422 in Temperature Range 25–250 °C
4. Conclusions
- ABaX422 alloy in the as-cast condition has a limited workability, due to a coarse and large-grained microstructure, and cannot be hot worked at higher speeds without causing microstructural damage.
- The processing map for the as-cast ABaX422 alloy offers a window, at temperatures higher than 400 °C and strain rates lower than 0.3 s−1, where the alloy may be hot worked.
- A connected step of extrusion has been designed by selecting a process parameter as per the processing map for the as-cast alloy, and extrusion of a 104 mm diameter billet has been conducted to produce a 12 mm diameter rod product, the microstructure of which has a finer grain size with a redistributed fine particles of the intermetallic phases.
- The processing map for the extruded alloy exhibited four domains—two of them, representing dynamic recrystallization, are similar to those exhibited in the processing map for as-cast material, while the remaining two only appear with the extruded material.
- Out of the two new domains exhibited in the map for the extruded alloy, the one occurring in the temperature range 360–420 °C and strain rate range 0.2–10 s−1 (Domain 3) is useful for manufacturing, since the strain rate is higher, making the process viable, and the temperature is lower, resulting in a finer grain size in the product.
- The fourth domain that occurs at temperatures higher than 440 °C and strain rates higher than 0.2 s−1 represents intercrystalline cracking and causes reduced workability.
- The area of the flow instability regime exhibited in the processing map for the as-cast alloy is reduced by the extrusion step, and this enlarges the workability window.
- Connected process design by changing the constitutive response of hard-to-process alloys may be used to manufacture wrought components at viable speeds and with better mechanical properties.
Author Contributions
Acknowledgments
Conflicts of Interest
References
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Condition | Yield Strength (MPa) | Ultimate Tensile Strength (UTS), MPa | Strain to Fracture | Maximum Displacement (mm) | % Elongation |
---|---|---|---|---|---|
Domain 1 (380 °C and 0.0003 s−1) | 41 | 50 | 0.47 | 19.25 | 47% |
Domain 2 (500 °C and 0.0003 s−1) | 2 | 6 | 0.82 | 32.89 | 84% |
Domain 3 (380 °C/2.3 s−1) | 80 | 121 | 0.35 | 17.61 | 35% |
Domain 4 (500 °C/2.3 s−1) | 50 | 64 | 0.49 | 19.64 | 48% |
Domain # | As-Cast (Ref. [13]) | Extruded | ||||
---|---|---|---|---|---|---|
n | Q (kJ/mole) | Mechanism | n | Q (kJ/mole) | Mechanism | |
1 | 5.24 | 169 | Climb (LSD) | 5.37 | 138 | Climb (LSD) |
2 | 4.46 | 263 | Cross-slip | 3.49 | 182 | Cross-slip |
3 | - | - | - | 5.05 | 140 | Climb (GSD) |
4 | - | - | - | 4.54 | 148 | GB cracking |
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Rao, K.P.; Chalasani, D.; Suresh, K.; Prasad, Y.V.R.K.; Dieringa, H.; Hort, N. Connected Process Design for Hot Working of a Creep-Resistant Mg–4Al–2Ba–2Ca Alloy (ABaX422). Metals 2018, 8, 463. https://doi.org/10.3390/met8060463
Rao KP, Chalasani D, Suresh K, Prasad YVRK, Dieringa H, Hort N. Connected Process Design for Hot Working of a Creep-Resistant Mg–4Al–2Ba–2Ca Alloy (ABaX422). Metals. 2018; 8(6):463. https://doi.org/10.3390/met8060463
Chicago/Turabian StyleRao, Kamineni Pitcheswara, Dharmendra Chalasani, Kalidass Suresh, Yellapregada Venkata Rama Krishna Prasad, Hajo Dieringa, and Norbert Hort. 2018. "Connected Process Design for Hot Working of a Creep-Resistant Mg–4Al–2Ba–2Ca Alloy (ABaX422)" Metals 8, no. 6: 463. https://doi.org/10.3390/met8060463