Abstract
AZX312 (AZ31-2Ca) magnesium alloy, with starting conditions of as-cast (AC), cast-homogenized (CH), and disintegrated melt deposition (DMD), is examined in terms of its compressive strength and hot working behavior to establish the relative merits and limitations of these processing routes. Processing maps are developed in the temperature range of 300–500 °C and strain rate range of 0.0003–10 s−1, and mechanisms of hot deformation are established based on microstructures, tensile ductility, and activation parameters. The alloy in AC and CH conditions has a large grain size with intermetallic phases at the grain boundaries and in the matrix. In DMD processed alloy, the grain size is very small and the phases are refined and distributed uniformly. The compressive strength is significantly improved by DMD processing, which is attributed to the grain refinement. The processing maps for AC and CH conditions are similar, exhibiting only a single workability domain, while the DMD processed alloy exhibited three domains that enhanced workability. The additional workability domain at higher strain rates is an advantage in designing forming processes that facilitates faster production, while the fine grain size produced by a finishing operation in the lower temperature domain will improve the mechanical properties of the product.
Highlights
Due to their light weight, magnesium alloys are attractive as structural components in auto and aerospace industries [1], and Mg-3Al-1Zn (AZ31) has been investigated extensively [2,3,4,5] in view of its commercial popularity
The ultimate compressive strength of the alloy processed by the above routes is compared in the temperature range of 25–250 ◦ C, while the hot working behavior is characterized using the technique of the processing map, developed in the temperature range of 300–500 ◦ C and a strain rate range of 0.0003–10 s−1
Processed alloy has shown two significant changes in the hot working behavior compared to AC: (1) A window (Domain #2) for hot working the alloy became available at higher strain rates, which may be used for faster production as required in manufacturing; and (2) A lower temperature window (Domain #1A) for finishing operations so that finer grain size is achieved in the product
Summary
Due to their light weight, magnesium alloys are attractive as structural components in auto and aerospace industries [1], and Mg-3Al-1Zn (AZ31) has been investigated extensively [2,3,4,5] in view of its commercial popularity. The ultimate compressive strength of the alloy processed by the above routes is compared in the temperature range of 25–250 ◦ C, while the hot working behavior is characterized using the technique of the processing map, developed in the temperature range of 300–500 ◦ C and a strain rate range of 0.0003–10 s−1. The principles and procedure of the developing of the processing map has been described earlier [18,19,20] In this model, the material undergoing hot deformation is a non-linear dissipator of power and the strain rate sensitivity (m) of flow stress is the factor that partitions the power between the deformation heat and the microstructural dissipation. The map exhibits domains where the workability of a material is optimal, such as dynamic recrystallization (DRX), and regimes of flow instabilities
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