Microstructural Inhomogeneity in the Fusion Zone of Laser Welds.

This paper investigated evolutions of α-Al sub-grains' morphology and crystalline orientation in the fusion zone during laser welding of 2A12 aluminum alloys. Based on this, a new method for assessing the weldability of materials was proposed. In laser deep-penetration welding, in addition to the conventional columnar and equiaxed dendrites, there also exhibited a corrugated structure with several 'fine-coarse-fine' transformations. In such regions, an abnormal α-Al coarsening phenomenon was encountered, with a more dispersed crystalline orientation arrangement and a decreased maximum pole density value. Particularly, structural alterations appeared more frequently in the weld bottom than the top. The above results indicated that the laser-induced keyhole presented a continually fluctuating state. Under such a condition, the solid-liquid transformation exhibited an unstable solidification front, a fluctuant undercooling, and a variational solidification rate. Meanwhile, the welding quality of this material is in a critical state to generate pores. Therefore, the appearance and relevant number of corrugated regions can be considered as a new way for judging the weldability, which will help to narrow the processing window with better welding stability.

Advances in the Welding of Aluminum Matrix Composites: A New Open Special Issue in Materials.

"Advances in the Welding of Aluminum Matrix Composites" is a new open Special Issue of Materials that aims to publish original research and review papers on new scientific and applied research and to make great contributions to advances in the field of welding aluminum matrix composites as well as to the related synthesis, fundamentals, characterization, and application of these materials [...].

Microstructure Evolution and Mechanical Properties of 20%SiCp/Al Joint Prepared via Laser Welding.

SiC particles-reinforced Al matrix composites (SiCp/AMCs) have been widely used in the aerospace structural components. In this work, 20 vol% SiCp/2A14 joint was fabricated by laser welding technology. The effects of different laser power/welding velocity on the 20 vol% SiCp/2A14 joint forming, microstructure evolution and mechanical properties were studied in detail. The results showed that, under the same heat input, the high power/high welding velocity was beneficial to reduce the porosity of SiCp/2A14 joint and inhibited the formation of brittle phase of Al4C3. At 8 kW-133 mm/s welding parameters, the maximum tensile strength of the SiCp/2A14 joint reached 199 MPa, which is ~64% higher than that of the SiCp/2A14 joint prepared at 4 kW-66 mm/s welding parameters. By analyzing the fracture morphology and SEM image of SiCp/2A14 joint section, it is was found that the porosity of weld and Al4C3 brittle phase were the important factors limiting the strength of SiCp/2A14 joint. This work provides a reference for the process window design of laser welding SiCp/2A14 composites.