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.
Highlights
Magnesium alloys are the lightest commercially-used metals, offer excellent cast-ability, machinability, low density, high specific strength and stiffness, electromagnetic shielding characteristics and are, attractive for applications in the transportation industry, electronic products, portable tools, sporting goods and aerospace vehicles [1,2,3]
In the authors’ previous investigations, uniform distribution and dispersion of fine-grained, in situ Mg2Sip/AM60B composite have been achieved via traditional gravity casting by the addition of 0.5 wt% Sr and 0.2 wt% SiCp [16]
The informative results are compared with identical as-cast composites and thixoforged AM60B alloy, in order to elucidate the strengthening mechanisms of the thixoforging technique and Mg2Si particles
Summary
Magnesium alloys are the lightest commercially-used metals, offer excellent cast-ability, machinability, low density, high specific strength and stiffness, electromagnetic shielding characteristics and are, attractive for applications in the transportation industry, electronic products, portable tools, sporting goods and aerospace vehicles [1,2,3]. Metal-matrix composites possess many advantages over monolithic materials, such as high-temperature mechanical strength, good wear resistance and dimensional stability, and they have been widely used in aircraft, space, defense and automotive industries [4,5]. In the authors’ previous investigations, uniform distribution and dispersion of fine-grained, in situ Mg2Sip/AM60B composite have been achieved via traditional gravity casting by the addition of 0.5 wt% Sr and 0.2 wt% SiCp [16]. The microstructure, tensile properties and fracture behavior of in situ Mg2Sip/AM60B composite are studied. The informative results are compared with identical as-cast composites and thixoforged AM60B alloy, in order to elucidate the strengthening mechanisms of the thixoforging technique and Mg2Si particles
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