In-situ observation of damage evolution and fracture in AlSi7Mg0.3 cast alloys

Effect of Solution Heat Treatments on the Microstructure and Mechanical Properties of a Die-Cast AlSi7MgMn Alloy

“…Slip bands appear between adjacent cracks. As reported by Mishnaevsky et al, [18] the necking along the slip bands between the microcracks is the main mechanism for their coalescence, and the microcrack coalescence is the origin of the reduction of the load-bearing area. Microcrack coalescence is observed only after slip bands have formed between them and not due to their expansion or growth.…”

“…[10,12,13] These microstructural transformations (to some extent) have an effect on the ductility of the alloy, i.e., they increase the fracture strain, as they make it more difficult for the silicon particles to fracture. [17][18][19][20][21] In this study, the combined effect of the solution temperature (475°C and 525°C) and the time (in the range of 15 to 480 minutes) on the microstructure, tensile properties, hardness, and fracture mode of a Sr-modified die-cast AlSi7MgMn alloy was investigated. A comparison between a short (15 to 60 minutes) and prolonged solution heat treatment (240 to 480 minutes) was then carried out; this described how the aluminum alloy die castings may be solution heat treated at high temperature without encountering problems with blistering.…”

A study on nano-deformation behavior of rheo-formed Al–Si alloy based on depth-sensing indentation with three-dimensional surface analysis

“…This indicates that the hardness of the elongated particles was greater than that of the matrix material. When a ductile material is reinforced by a dispersion of elastic rigid particles such as Si-particles, incompatibility stresses develop in both the particles and the matrix [7,9]. These stresses result from the differences in elastic constants as well as from differences in deformation behavior.…”

“…The model developed by Yeh and Liu to describe the failure of Si-particles in their AlSi7Mg alloys explains the microcrack initiation as a result of particle failure caused by stress concentrations originating from dislocation pile-ups of these particles. Mishnaevsky et al [9] reported that microcracks are initiated predominantly by the failure of Si-particles caused by dislocation pile-ups. They also reported that microcracks are oriented mainly along the lines of maximum shear stress.…”

“…The region of interest in the failure process is the eutectic region in which crack initiation begins with initial fracture of the eutectic silicon particles and inside other intermetallic phases. The brittleness of coarse Si crystals (both eutectic and primary Si) is the main reason for the poor properties of Al-Si alloys, because coarse Si crystals lead to premature crack initiation and fracture in tension [7][8][9][10]. The silicon particles are very brittle and, therefore, cannot accommodate the plastic deformation of the surrounding matrix because incompatibility stresses develop in both the particles and the matrix.…”