The Influence of Prior Natural Aging on the Subsequent Artificial Aging Response of Aluminium Alloy A356 with Respective Globular and Dendritic Microstructures

Abstract

Alloy A356 is one of the most popular alloys used for semisolid metal forming. The heat treatment cycles that are currently applied to semisolid processed components are mostly those that are in use for dendritic casting alloys. The assumption has been made that these heat treatments are not necessarily the optimum treatments, as the difference in solidification history and microstructure of SSM processed components should be considered. The objective of this study is to determine whether dendritic A356 behaves in a similar way to globular A356 in terms of its response to artificial aging with or without prior natural aging. The results indicate that the differences in microstructures (globular or dendritic) do not have a noteworthy effect on the heat treatment response. It is also shown that strong linear correlations are found between T4 and T6 hardness and wt% Mg of A356, regardless of the casting technique used.

Factors Influencing Tensile Mechanical Properties of Al‐7Si‐Mg Casting Alloys A356/7

“…Plates with varying Mg-contents [7][8][9][10][11] and automotive brake callipers [12] were cast using either a 50, 130 or 630 ton clamping force high pressure die casting (HPDC) machine. In order to study these alloys with dendritic microstructures, gravity die cast (GDC) automotive brake callipers [12] and investment cast (IC) plates [13] were used. The "traditional heat treatment of 540°C for 6 h and artificial aging for 170°C for 6 h, as well as CSIR developed [7][8][9][10][11][12] shortened heat treatments of 540°C for 1 h, natural pre-aging (NA) of 0-120 h and artificial aging for 180°C for 4 h were employed.…”

“…-*^J An artificial aging time of 29 h may be prohibitively long and therefore artificial aging parameters of 180°C for 4 h are suggested as the optimum for SSM-HPDC alloys A356 and F357 [7][8][9][10][11][12] and for dendritic A356 and F357 [11,13], without a significance decrease in hardness compared to 160°C (Fig. 8).…”

“…2,3 varied between 6.6-7.3%[7][8][9][10][11][12][13] i.e. covering almost the whole range of 6.5-7.5% allowed in the specification…”

Towards the Prediction of Tensile Properties in Automotive Cast Parts Manufactured by LPDC with the A356.2 Alloy

“…Thus, two sets of data from Möller et al [36,37], and another one from Fortini et al [38], have been also analyzed in the present work to determine the effect of Mg content on tensile properties of A356 alloys and to compare them with data obtained from castings produced in the present work. Although Möller et al [36,37] used semi-solid metal (SSM) slurries directly prepared from the liquid alloy to produce 4 mm × 80 mm × 100 mm plates by HPDC facility, they also reported similar artificial aging T6 responses for same automotive brake calipers manufactured using both SSM-A356 alloys with globular microstructures and A356 alloys in gravity die casting, this last leading to dendritic microstructures with SDAS values of about 20 µm [39]. In case of A356 alloys prepared by Fortini et al [38], they were cast in a preheated die to produce castings with dendritic microstructures.…”

Comparison of the Heat Treatment Response of Wrought and SSM-HPDC Alloy 6082

“…However, one of the main advantages of SSM processing is that it is also possible to produce near net-shape components from alloys that are conventionally wrought, such as the 6000 series Al-Mg-Si alloys [2]. It has recently been shown by the authors that the aging response of SSM-HPDC A356 (with globular microstructure) does not differ from that of conventional liquid cast A356 (with dendritic microstructure) [3,4]. The purpose of this paper is to compare the aging response of SSM processed 6082 with that of conventional wrought 6082.…”