Improved Elevated Temperature Properties in Al-13%Si Piston Alloys by Mo Addition

Abstract

Eutectic Al-13%Si alloys are widely used in the automotive industry for manufacturing components, such as pistons and cylinder heads. To reduce greenhouse gas emissions and enhance the engine efficiency, their service temperature keeps increasing to 250-350 °C, leading to the deterioration of their mechanical properties and the creep resistance. In the present work, Mo was further added to Mn-containing Al-13%Si piston alloys aiming at improving the overall properties at elevated temperatures. Compared with the Mn-containing base alloy, Mo further enhanced the precipitation of dispersoids by expanding the dispersoid zone and restricting the dispersoid-free zone after the proper precipitation treatment (520 °C/12 h), resulting in a remarkable improvement in the yield strength at both room temperature and 300 °C, as well as the creep resistance at 300 °C. Furthermore, the beneficial effect of Mo addition on the improved yield strength and creep resistance was especially prominent during long-term thermal exposure (up to 1000 h at 300 °C) due to the synergistic effect of thermally stable dispersoids and the retardation of the gradual fragmentation and spheroidization of Si particles.

Evolution of microstructure and elevated-temperature properties during hot rolling and post-rolling annealing process in Al-Mg-Si 6082 alloys

“…1c) and they were even much finer with increased number density after rolling ( Fig. 2e), which were reported to strongly inhibit the recrystallization through increasing the Zener drag force due to its finer size and higher number density [4,16]. Therefore, the recrystallization in Alloy B was greatly retarded (Fig.…”

“…Therefore, how to improve the elevatedtemperature properties of Al-Mg-Si 6xxx aluminum alloys has been highlighted as one of the industrial key concerns. On the other hand, the introduce of thermalstable dispersoids during the proper heat treatment is proved to greatly improve the elevated-temperature properties in 3xxx and 4xxx alloys [2][3][4][5]. Though the evolution of dispersoids are also investigated in Al-Mg-Si 6xxx alloys [6][7][8], most of them focused on the influence of dispersoids on the recrystallization behaviors at room temperature and the role of dispersoids on the elevated-temperature mechanical properties of 6xxx aluminum alloys is rarely discussed.…”

Influence of transition elements (V, Zr and Mo) and cooling rate on the precipitation of dispersoids in Al-7Si-0.6Cu-0.35Mg foundry alloy

“…In Al-Si foundry alloys, the dispersoids usually form during solution treatment [1,4,18,23]. To monitor the precipitation of dispersoids during solution treatment and to compare the hardening effect of the transition elements, Vickers microhardness (HV) and electrical conductivity (EC) as a function of holding time were measured and the results are shown in Fig.…”

“…Therefore, how to improve the elevatedtemperature properties of Al-Si foundry alloys is of primary importance for their sustainable development. On the other hand, the dispersion strengthening of thermally stable dispersoids has been proved to be one of the best strengthening ways for Al-Si alloys at elevated temperature [1,3,4].…”

“…It is recently discovered that Mo is a supreme dispersoid former in both aluminum foundry and wrought alloys [1,3,4,18]. The combination of Mn and Mo can lead to a uniform distribution of partially coherent α-Al(Mn,Mo,Fe)Si dispersoids and reduce the dispersoid free zone, because of their opposite solidliquid partition coefficient during solidification [18].…”