Guangdong Academy of Sciences

The influence of pre-deformation on the microstructure and mechanical properties of a Mg-rich high-Cu Al-Mg-Si-Cu alloy was systematically investigated by hardness measurement, tensile test, and atomic resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). With the increase in pre-deformation strain (0–10%), the hardness and strength of the alloy after PB hardening increased progressively, accompanied by a continuous reduction in tensile elongation. Notably, increasing pre-deformation strain from 2% to 10% did not bring a significant enhancement in bake hardening response, despite the gradual improvement in the strain hardening capability of the alloy. An optimal pre-deformation strain of 5% is identified, which enabled the alloy to achieve a superior and industrially feasible combination of strength and ductility, balancing practical forming demand (T4 temper) and service performance (PB state). Pre-deformation can significantly affect the morphology and atomic structure of precipitates for the alloy. Dislocations introduced by pre-deformation acted as heterogeneous nucleation sites, inducing the formation of elongated and string-like precipitates along dislocation lines. A distinct Cu segregation behavior was observed in the pre-deformed alloy with the majority of Cu atoms segregated at the precipitate/α-Al interface, which was in sharp contrast to their dominant distribution within the precipitate interior in the non-pre-deformed alloy. These findings provide new insights into deformation-assisted precipitation regulation in Mg-rich high-Cu Al-Mg-Si-Cu alloys and offer practical guidance for optimizing the strength–ductility synergy of such alloys for automotive lightweight manufacturing applications.

Abstract Hexavalent chromium [Cr(VI)] is a heavy metal that poses serious environmental risk. Microbial Cr(VI) reduction is a potential remediation approach to reduce the mobility and toxicity of this metal in the environment. However, the diversity and metabolic mechanisms of Cr(VI)-reducing bacteria (CrRBs) remain unknown. In this study, a combination of enrichment incubation and high-throughput sequencing was used to elucidate CrRBs and their associated metabolic pathways for Cr(VI) reduction. Enrichment incubation identified bacterial populations belonging to Cellulomonas, Enterobacter, Rikenellaceae , and Citrifermentans as putative CrRBs in the two Cr(VI)-contaminated sediments and paddy soils as they gradually dominated the microbial community. High-quality metagenome-assembled genomes (MAGs) associated with putative CrRBs were reconstructed, and functional genes responsible for Cr(VI) reduction were detected, suggesting that they are putative CrRBs. This study advances our understanding of CrRBs diversity and their underlying metabolic mechanisms.