A Comparative Characterization of the Microstructures and Tensile Properties of As-Cast and Thixoforged in situ AM60B-10 vol% Mg2Sip Composite and Thixoforged AM60B

Abstract

Abstract:The microstructure and tensile properties of the thixoforged in situ Mg2Sip/AM60B composite were characterized in comparison with the as-cast composite and thixoforged AM60B. The results indicate that the morphology of α-Mg phases, the distribution and amount of β phases and the distribution and morphology of Mg2Si particles in thixoforged composite are completely different from those in as-cast composite. The Mg2Si particles block heat transfer and prevent the α-Mg particles from rotation or migration during reheating. Both the thixoforged composite and thixoforged AM60B alloy exhibit virtually no porosity in the microstructure. The thixoforged composite has the highest comprehensive tensile properties (ultimate tensile strength (UTS)) of 209 MPa and an elongation of 10.2%. The strengthening mechanism of the Mg2Si particle is the additive or synergetic effect of combining the load transfer mechanism, the Orowan looping mechanism and the dislocation strengthening mechanism. Among them, the load transfer mechanism is the main mechanism, and the latter two are minor. The particle splitting and interfacial debonding are the main damage patterns of the composite.

Solution Treatment Behaviors of 6061 Aluminum Alloy Prepared by Powder Thixoforming

“…When the PTF alloy was subjected to solution treatment at 560ºC for 3h, lots of flat facets that resulted from cracks propagating across primary α-Al phases appeared (Fig.9b). This indicated that the fracture of PTF alloy may follow a transgranular mode at this time, which was a sign of improved tensile strengths for the thixoformed materials 22,25 . Besides, the amount of the dimples became less but its size was observed to be larger than the as-fabricated state, suggesting an improvement in the elongation of the PTF alloy after solution treatment.…”

Mechanical Properties of Thixoforged In Situ Mg2Sip/AM60B Composite at Elevated Temperatures

“…Therefore, the UTS of the thixoforged AM60B decreases at 150 °C owing to the absence of a reinforcing phase for the matrix (Figure 2). As mentioned above, the Mg2Si particle always locates in the last solidified regions [20], i.e., surrounded by the eutectic phase. Thus, the softening of the eutectic β phase leads to the decrease in the interfacial bonding strength between the Mg2Si particles and the matrix.…”

Casting Alloy Design and Modification

“…This can be achieved by alloying and by the addition of particles formed in-situ and ex-situ [4][5][6]. New processes are also entering the manufacturing scene affording new possibilities to create novel microstructures and thereby also new types of property combinations [6,7]. The introduction of new processes also shifts the boundary between processes that used to be made in fully solid state and now move towards casting and more liquid processing resulting in hybrid processes [6][7][8].…”

“…New processes are also entering the manufacturing scene affording new possibilities to create novel microstructures and thereby also new types of property combinations [6,7]. The introduction of new processes also shifts the boundary between processes that used to be made in fully solid state and now move towards casting and more liquid processing resulting in hybrid processes [6][7][8]. Independent of this, post treatment processes for bulk and surface properties are still needed to be used together with the novel processing property capability [8,9].…”

“…Once the part is produced with appropriate soundness then the microstructure should be suitable for the job. This can be achieved by alloying and by the addition of particles formed in-situ and ex-situ [4][5][6]. New processes are also entering the manufacturing scene affording new possibilities to create novel microstructures and thereby also new types of property combinations [6,7].…”