Influence of metal matrix powder size on the tensile strength of a SiC_p/AlSi7Mg0,6 composite produced by field assisted sintering technique

Abstract

In the present study, 35vol% SiCp/AlSi7Mg0,6 composites were prepared using field assisted sintering technique in order to investigate the effect of different particle fractions and size distributions of the AlSi7Mg matrix powder on the tensile properties of the produced composite material. In most usecases the size of the reinforcement phase is given by the application and is only variable within narrow limits (< 20pm particle size in this work). On the other hand, there is potential for optimization of the matrix powder. In this investigation, fine (d50 = 25 µm), coarse (d50 = 52 µm), bimodal (50wt% of fine + 50wt% of coarse, d50 = 36 µm) and as received (d50 = 40 µm) aluminum powder was used as the matrix powder. Using fine matrix powder has improved yield strength by 5 % and ultimate tensile strength by 7 % compared to the as received condition. This is largely due to the lower porosity of the composite produced under the use of the fine matrix powder ((0.07 ± 0.04) %) in contrast to the composite using the as received aluminum powder ((0.62 ± 0.35) %). At the same time, the consumed heating energy of the composite was decreased by almost a third when using the fine matrix powder in comparison to the use of the as-received matrix powder. This paper presents results of an optimization approach for mechanical properties of aluminum matrix composites without any changes of the sintering parameters.

Investigation of the Tribological Behaviour of Various AMC Surfaces against Brake Lining Material

“…For the AMC production, gas-atomised AlSi7Mg cast alloy powder was selected as the matrix material, and 35 vol.% SiC particles (F400) were used as reinforcement for the aluminium composite. The mixed composite powder was consolidated by a field-assisted sintering process, in analogy to [ 19 ], to disc samples with a diameter of 200 mm and a height of 12 mm up to 14 mm. A typical microstructure of an AMC disc is represented in Figure 1 a.…”

Towards Closed-Loop Recycling of Ceramic Particle-Reinforced Aluminium Alloys: Comparative Study of Resistance-Heating Sintered Primary and Solid-State Recycled Secondary SiCp/AlSi7Mg Composites

“…Compared to the initial AMC condition (as-received), the tensile strength of the sintered AMC using a CM fraction is reduced by about 30% and that for an MM fraction by about 60%. It can be assumed that a weaker bonding between the heterogeneous areas, i.e., between the filler and coarse or medium particulate phase, respectively, leads to failure already at lower stresses since the observed small variation of the present porosity level does not strongly affect the AMC strength [9]. In general, the strength values of the recycled conditions scatter more strongly than those obtained for the initial as-received AMC.…”

“…The three AMC fractions "coarse", "middle", and "filler" (milled chips) are described in detail in Table 1. Since the bulk density has a noticeable influence on the subsequent sintering result, it was measured for all fractions, as described in [9]. For calculation of the relative density, the measured values were put into ratio with the density of 2.86 g/cm 3 corresponding to an ideal AMC body of this specific composition.…”

“…This specific characteristic of high-particle-reinforced AMC materials makes their mechanical recycling possible. It is to be expected that the initial microstructure of a high-particle-reinforced AMC can be maintained during a solid-state recycling process due to its low deformation capacity (toughness) [9] and brittle cracking behaviour [10]. In this study, mechanical recycling is defined as a simple crushing or milling process that is not prone to (significantly) change the local chemical composition and general properties of the recycled AMC.…”

Heat Treatment Influencing Porosity and Tensile Properties of Field Assisted Sintered AlSi7Mg0.6

“… Cutting of the FAST sample for ( a ) measuring the surface Brinell hardness and the orientation of the cross section used for microscopic analysis (marked in grey), and ( b ) orientation of the extracted tensile specimens and their geometry, after [ 20 ]. …”