Three-dimensional rigid multiphase networks providing high-temperature strength to cast AlSi10Cu5Ni1-2 piston alloys

Abstract

The three-dimensional (3-D) architecture of rigid multiphase networks present in AlSi10Cu5Ni1 and AlSi10Cu5Ni2 piston alloys in as-cast condition and after 4 h spheroidization treatment is characterized by synchrotron tomography in terms of the volume fraction of rigid phases, interconnectivity, contiguity and morphology. The architecture of both alloys consists of α-Al matrix and a rigid long-range 3-D network of Al7Cu4Ni, Al4Cu2Mg8Si7, Al2Cu, Al15Si2(FeMn)3 and AlSiFeNiCu aluminides and Si. The investigated architectural parameters of both alloys studied are correlated with room-temperature and high-temperature (300 °C) strengths as a function of solution treatment time. The AlSi10Cu5Ni1 and AlSi10Cu5Ni2 alloys behave like metal matrix composites with 16 and 20 vol.% reinforcement, respectively. Both alloys have similar strengths in the as-cast condition, but the AlSi10Cu5Ni2 is able to retain ∼15% higher high temperature strength than the AlSi10Cu5Ni1 alloy after more than 4 h of spheroidization treatment. This is due to the preservation of the 3-D interconnectivity and the morphology of the rigid network, which is governed by the higher degree of contiguity between aluminides and Si.

Effects of Sr content on the microstructure and mechanical properties of cast Al–12Si–4Cu–2Ni–0.8Mg alloys

“…Three kinds of Ni-phases including Al 3 CuNi, AlSiFeNiCu-Aluminide [21] and Al 7 Cu 4 Ni are detected in test alloys. The Al 7 Cu 4 Ni phase (Label 1 and 6) can be seen white bone-like morphology in Fig.…”

Revealing the Effect of Local Connectivity of Rigid Phases during Deformation at High Temperature of Cast AlSi12Cu4Ni(2,3)Mg Alloys

“…The strength of cast Al-Si piston alloys is given by the strength of the age-hardenable α-Al matrix and the load carrying capability of interconnected 3D hybrid networks formed by Si and various intermetallic phases [1,2,3,4,5]. The alloying elements Cu and Mg play a decisive role on precipitation strengthening of the matrix, while, together with Ni, they define the interconnectivity of the 3D networks [6,7,8,9].…”

The effect of spheroidisation heat treatment on the creep resistance of a cast AlSi12CuMgNi piston alloy

“…1). Three dimensional studies of the microstructure of similar piston alloys and cast AlMgSi alloys indicate that the largest decrease in the interconnectivity of the eutectic Si takes place during the first 1-4 h of solution treatment [13,[24][25][26]. Table 2 reveals the reason for the different reported creep exponents.…”

“…The latter are highly contiguous with the eutectic Si [12] and partially hinder the spheroidisation of Si. This effect maintains the load bearing capability and the strength of the alloy [13].…”