Evolution of Elevated-Temperature Strength and Creep Resistance during Multi-Step Heat Treatments in Al-Mn-Mg Alloy

Abstract

The present work has systematically investigated the evolution of dispersoids and elevated-temperature properties including strength and creep resistance during various multi-step heat treatments in Al-Mn-Mg 3004 alloys. Results show that only the α-Al(MnFe)Si dispersoid is observed in the studied temperature range (up to 625 °C), and that it coarsens with increasing temperature to 500 °C, but dissolves at 625 °C. The evolution of elevated-temperature strength and creep resistance is greatly related to the temperature of each step during the multi-step heat treatments. Generally, lower temperature at the first-step heat treatment leads to higher properties, while the properties decrease with increasing temperature of last-step heat treatment. Suitable models have been introduced to explain the evolution of strength and the creep threshold stress at elevated-temperatures during the various heat treatments.

Superplastic Behavioral Characteristics of Fine-Grained 5A70 Aluminum Alloy

“…There was a transition between the metastable β-Al 2 Mg phase and the β-Al 3 Mg 2 phase with a hexagonal structure in the dynamic stretching process, as shown in Figure 11c [65]. Figure 11b,d indicate that the Al 6 (MnFe) phase disperses after all the heat treatments [30,66], and the Mg 5 Si 6 phase precipitated during the superplastic deformation. Similar dispersed phase particles were previously observed in the aluminum-magnesium-silicon alloys [67,68].…”

Enhanced Elevated-Temperature Strength and Creep Resistance of Dispersion-Strengthened Al-Mg-Si-Mn AA6082 Alloys through Modified Processing Route

“…Figure 1 shows the evolution of the dispersoids under various conditions in both the 0.5 Mn and 1 Mn alloys. For the 0.5 Mn alloy homogenized at 400 °C for 5 h ( Figure 1 a), numerous fine α-Al(FeMn)Si dispersoids (cubic with a = 1.265 nm [ 6 ]) with an average equivalent diameter ( ) of ≈25 nm precipitated in the Al matrix. During the conventional extrusion at 500 °C ( Figure 1 b), the fine dispersoids obtained after homogenization experienced substantial coarsening, as their increased from ≈25 nm after homogenization at 400 °C/5 h to ≈40 nm after extrusion (0.5Mn(LH)).…”

“…In Al-Mg-Si-Mn 6xxx alloys, the typical dispersoids formed during homogenization are α-Al(FeMn)Si, appearing with either simple cubic or body-centered cubic structures [ 5 , 6 ]. These dispersoids tend to form during heating and become relatively coarse (≈200 nm in equivalent diameter) during the soaking stage of industrial homogenization treatments typically conducted above 540 °C [ 5 , 7 , 8 ].…”

Improvement of elevated-temperature strength and recrystallization resistance via Mn-containing dispersoid strengthening in Al-Mg-Si 6082 alloys

“…Orowan mechanism [24][25][26] , but it is still too far to provide satisfactorily quantitative results. The strengthening mechanisms at elevated temperature are more complex than the room temperature because there is sufficient thermal energy to allow more activities happen, such as the higher vacancy and solute diffusion, higher grain boundary movement and the activation of multi-slip systems for dislocations, etc.…”