Rheocasting of Al-Cu Alloy A201 with Different Silver Contents

Abstract

Rheocasting of alloys A206 and A201 was investigated in this study. Conical bars with different silver contents were produced using CSIR rheoprocess technology, together with high pressure die casting. The results showed that addition of Ag to alloy A206 increased the mechanical properties of the alloy. However, the addition of Ag also resulted in Cu-rich phases to precipitate at the grain boundaries of the as-cast material. The solution treatment used in this study was unable to dissolve all of this phase, especially in the 1.12%Ag-containing alloy. This resulted in slightly decreased mechanical properties compared to the 0.63%Ag-containing alloy. The T6 mechanical properties (strength and elongation) obtained in this study for rheocast A206 and A201 are better than those reported for permanent mould castings of alloy A206 and A201.

Optimisation of heat treatment of Al–Cu–(Mg–Ag) cast alloys

“…At the optimal ageing temperature, the alloy reaches the peakageing hardness value within an adequate time, while, on the other hand, lower temperatures require a relatively long time to reach the peak; at higher temperatures, precipitates turn into relatively large non-coherent particles offering low strength (over-aged) [18]. In previous works, Al-Cu-Mg-Ag alloys were artificially aged at a quite wide temperature range from 150 to 250°C to identify the peakageing condition [19][20][21][22]. The peak-ageing temperature was changed by changes in concentration of Cu, Mg and Ag in the alloy [20].…”

The Heat Treatment of Rheo-High Pressure Die Cast Al-Cu-Mg-Ag Alloy 2139

“…Al-Cu-Mg-Ag-Mn alloys are generally given a two-step homogenization/solution treatment before artificial aging [2,5,7]. Cho and Bes [2] homogenized their 2139 alloy ingots at 521 o C for 24 h and performed a subsequent solution treatment at 530 o C for 30 minutes.…”

“…Cho and Bes [2] homogenized their 2139 alloy ingots at 521 o C for 24 h and performed a subsequent solution treatment at 530 o C for 30 minutes. The Ag-containing casting alloy 201, with a nominal composition of Al-4.6Cu-0.35Mg-0.7Ag-0.35Mn-0.25Ti, is commonly solution treated at 513 o C for 2 h, followed by 527 o C for 17 h [5]. Liu et al [7] found that the overburn temperature -where incipient melting occurs -for alloy 2039 (Al-5.3Cu-0.8Mg-0.5Ag-0.3Mn-0.15Zr) is 510 o C and they proposed that the upper temperature limit for homogenization is 500 o C. Semi-Solid Processing of Alloys and Composites XII [7], most likely corresponds to melting of Al 2 CuMg [8,9].…”

“…A NETZSCH STA 449F3 DSC was used with a heating rate of 10 o C/minute. Quenching after solution treatment was performed in room temperature water and artificial aging was done at either 153 o C for 20h [5] or 160 o C for 24 h [2].…”

“…Alloys 2024 and 2014 have been processed before [3,4], but these alloys are mainly strengthened by the S′/S-Al 2 CuMg and θ′ phases respectively, which are considered less desirable than Ω in terms of the alloy's all-round mechanical performance [1]. The Ag-containing wrought alloys such as 2139 have not, to the authors' best knowledge, been SSM-processed before, unlike the Ag-containing casting alloy 201 [5]. The purpose of this study is to rheo-high pressure die cast (R-HPDC) alloy 2139 and to determine its tensile mechanical properties in the T6 temper condition.…”