Constitutive Behavior of an AA4032 Piston Alloy with Cu and Er Additions upon High-Temperature Compressive Deformation

Abstract

Aluminum piston alloys of the AA4032 type are produced by direct-chill (DC) casting and subsequent forging; therefore, it is important to understand their thermomechanical behavior. In recent years, it was shown that additions of Cu and Er could improve mechanical properties of these alloys at room and high temperatures. In this work, we studied the constitutive behavior of AA4032-type alloys with and without Cu and Er additions. The experimental true stress-true strain curves were obtained by compression tests under various temperatures [683 K to 723 K (410°C to 450°C)] and strain rates (0.01 to 10 s À1) to determine constitutive parameters [strain-rate sensitivity, activation energy, and Zener-Hollomon (Z) parameter] for the hot deformation behavior of AA4032-type piston alloys with and without additions of Cu and Er. The flow stress decreased with increasing deformation temperature and decreasing strain rate. The results also showed that increasing the Cu content increased the flow stress over the applied range of deformation conditions due to solid-solution strengthening and the formation of primary Si particles, which led to an increase in the activation energy during hot deformation. Moreover, the main microstructural damage in the AA4032 alloy with 3.5 pct Cu was predominantly due to the cracking of primary Si particles. Additions of 0.4 pct Er and 3.5 pct Cu lower the activation energy of deformation, Q, as compared to the base alloy and the alloy with 3.5 pct Cu. The microstructures in the deformed specimens consisted of subgrains, recrystallized grains, and fine eutectic phases. The alloys containing Er demonstrated more polygonized grains at a low strain rate than the alloys without Er, indicating that Er hindered recrystallization development. The peak stress of the AA4032 alloy with 3.5 pct Cu alloy was higher than for the base AA4032 alloy and for the AA4032 alloy with 3.5 pct Cu and 0.4 pct Er additions, which was attributed to the prevalence of the work-hardening mechanism over the softening mechanism.

Comparative Analysis of Structure and Properties of Nb-B Inoculated Direct Chill Cast AA4032 Alloy Extruded from As-Cast and Homogenized Conditions

“…Phase composition presented in the Supplementary Table 1 is consistent with previous work on the 4032 alloy, 30 and also with the phase composition of multicomponent Al-Si piston alloys. 33 One should note that the Mg, Si, and Cu content in the fcc (Al) is consumed not only by Mg 2 Si phase but also by the eutectic (Si) and Fe-and Ni-bearing phases, which were observed in the BSD images presented in Figs.…”

“…29 Similar findings were observed in Ref. 30 focused on DC casting and the compressive deformation of the AA4032 alloy with Er addition. On the other hand, EDX line-scan analysis conducted on the homogenized sample (Fig.…”

“…36,37 Different studies give controversial information on the type of precipitates in AA4032 alloy. 3,30 For this reason, it is essential to carry out experimental investigations with TEM.…”

Hot Deformation Behavior of Novel Al-Cu-Y(Er)-Mg-Mn-Zr Alloys

“…Most of the publications have been devoted to investigating alloys with a small number of eutectic origin particles. However, it is known that such particles may significantly influence hot deformation behavior [29][30][31][32][33]. For example, it was found that the flow stress was lowered by decreasing the Al 3 Ni size at a low 0.03 volume fraction in binary Al-Ni alloys and intensive softening at large strains was achieved in the alloy with a 0.1 volume fraction of fine Al 3 Ni particles [29].…”

“…However, few works have been devoted to investigating the effect of the Y and Er content phases on the hot deformation behavior of Al-Cu alloys. Chankitmunkong et al showed that the AA4032 alloy with 3.5Cu and 0.4Er had a lower activation energy of deformation compared to the base alloy without Er [33]. The alloy with Er demonstrated more polygonized grains at a low strain rate than the alloys without Er, indicating that Er hindered recrystallization development [33].…”