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Al matrix composites (AMCs) are preferred engineering materials for aerospace and automotive industries owing to their high specific strength, superior wear resistance and low thermal expansion. It is a challenge to achieve high-quality fusion welded joints of AMCs because of the occurrence of defects such as pores, particles segregation and acicular phases. In this study, the effects of laser welding parameters including laser power, welding speed and laser incident angle on the formation of porosity and acicular phase were investigated in SiCp/6092 aluminum matrix composite welded joints using orthogonal experimental method. Range analysis of the orthogonal test results showed that the laser power and the welding speed had the greatest influence on the porosity and acicular phase size during the laser welding of aluminum matrix composites. At a heat input of 60 J/mm, the porosity in the weld was only 1.6% while that at 190 J/mm was 15.2%. Higher heat input produced a much larger size of brittle Al4C3 phases. The size of the acicular phase Al4C3 at the top and bottom of the weld was larger than that in the middle. Active Ti was added to the weld zone to mitigate the adverse effect of Al4C3 brittle phase and porosity on mechanical properties. The ultimate tensile strength increased from 115 MPa in direct laser welding to 148 MPa for the laser welding process employing the Ti interlayer. This work will provide referenceable data for designing high-quality AMC welded joints for aerospace and automotive industries.

The application of Mg–6Al–1Zn (wt.%, AZ61) alloy as biodegradable bone implant material is limited due to its too rapid degradation, which is largely related to the microgalvanic corrosion induced by the coarse island second phase in the alloy. In this study, cerium (Ce) was alloyed in AZ61 alloy by selective laser melting, aiming to enhance its degradation resistance. The microstructure characteristics were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The degradation behavior was studied by the electrochemical test and weight loss test. Besides, the mechanical properties and cytocompatibility of the alloy were also assessed. The results showed that Al preferentially reacted with Ce in the AZ61-Ce alloy because of the high electronegativity difference between Al and Ce and formed acicular Al 4 Ce phase due to the oriented crystal growth. Meanwhile, the consumption of Al in forming Al 4 Ce phase inevitably reduced the precipitation of island Mg 17 Al 12 phase. Compared with island Mg 17 Al 12 phase, the acicular Al 4 Ce phase possessed much larger ratio of length to the cross-sectional area, leading to a higher electrical resistance. As a consequence, the island-to-acicular alteration of second phase greatly decreased the corrosion current density, thereby enhancing the degradation resistance by about 7 times. In addition, the AZ61-Ce alloy presented improved compressive strength owing to the strengthening effect of the acicular second phase, as well as favorable biocompatibility. The island-to-acicular alteration of second phase may provide a method for the development of high performance biomedical Mg alloys. • Cerium (Ce) was alloyed in AZ61 alloy by selective laser melting. • Al preferentially reacted with Ce in the AZ61-Ce alloy and formed acicular Al 4 Ce phase. • The island-to-acicular alteration of second phase greatly decreased the corrosion current density. • The AZ61-Ce alloy presented improved compressive strength as well as favorable biocompatibility. [ABSTRACT FROM AUTHOR]