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The microstructural characteristics and low-temperature impact toughness of simulated reheat coarse grain heat affected zone (CGHAZ) of high strength medium-Mn steel were investigated based on thermal simulation. The results indicated that the impact energy of unaltered reheated CGHAZ (UA CGHAZ), supercritical reheated CGHAZ (SCR CGHAZ), intercritical reheated CGHAZ (ICR CGHAZ) and subcritical reheated CGHAZ (SR CGHAZ) at –40 °C was 38, 65, 26 and 9 J, respectively, and the microhardness was 376, 385, 400, and 329 HV, respectively, at welding heat input of 15 kJ/cm. Fine martensite lath microstructure and the high proportion of misorientation boundaries in SCR CGHAZ induced relatively higher impact toughness and microhardness. The microstructure of ICR CGHAZ had inferior uniformity and consisted of lath martensite with high dislocation density and lamellar twin martensite. Thereinto, twin martensite with higher hardness and less toughness deteriorated the ICR CGHAZ toughness. The segregation of Mn at grain boundaries reduced the adhesion between grain boundaries and led to severe embrittlement of SR CGHAZ. [ABSTRACT FROM AUTHOR]

A Ti3C2 MXene/Ti composite powder was developed through surface modification and powder coating for producing a high-performance titanium matrix composites (TMCs) by laser power bed fusion. Introducing MXene rarely changed the original sphericity and flowability of Ti powder while it slightly enhanced the laser absorption capacity of Ti powder. The printing conditions in turn affected the morphology and distribution of MXene in as-printed composites. At optimised printing parameters, majority of MXene with high structural integrity and uniform distribution remained along the grain boundaries of as-printed composites, and a combination of high surface quality, geometrical accuracy and densification was obtained. The remaining MXene played the synergy of pulling-out effect and load transfer role, which increased the yield strength from 530 to 710 MPa, while retaining good ductility (elongation of 19.8%). Compared with ASTM standard cast Ti64 alloy, our MXene/Ti composites also exhibited superior comprehensive tensile properties and excellent strength-ductility synergy. [ABSTRACT FROM AUTHOR]

High entropy alloys (HEAs), consisting of five or more elements with nearly equal atomic composition with one another (5–35%), are new-generation alloys that have attracted signifi)cant interest since their advent in 2004 because of their unique structural and mechanical properties and thermodynamic and chemical stability. Some characteristics, including high mechanical strength at elevated temperatures, high ductility and fracture toughness at cryo)genic temperatures and high corrosion, erosion and wear resistance, have been demonstrated for HEAs that outperform traditional alloys and superalloys. Laser-cladding (LC) is an additive manufacturing technique that has good feasibility in designing and processing HEAs for advanced structural components and protective coatings. This overview provides a glimpse of recent advances in LC of HEAs in terms of design fundamentals, metallurgical phase and microstructure, specific properties for advanced coating applications and the effect of ceramic particles reinforcement in LC deposition of HEA coatings. [ABSTRACT FROM AUTHOR]

Polycrystalline nanoparticles of Al-doped and Ce-co-doped ZnO were processed through sol)gel co-precipitation. Crystallite sizes determined from XRD were in the range of 10.90 to 48.77 nm. FTIR spectra indicated a stretching mode of Zn-O bond. The insertion of Al and Ce at Zn-O site created Al-O and Ce-O bonds. UV-vis spectra favoured the formation of impurity levels by doping and co-doping. Their overlapping with the conduction band edge led to the reduction of band-gap. Blue-green emission which arises from radiative recombination of a photogenerated hole with an electron occupying oxygen vacancy was observed in photo)luminescence spectra. FESEM suggested granular growth in undoped ZnO which changed to diverse structures such as nano-bar and cluster of elongated grains. Significant improvement in room temperature ferromagnetism (RTFM) was noticed by co-doping of Ce in Al-doped ZnO. Formation of bound magnetic polarons (Ce3+-Vo-Ce3+) was the primary mechanism responsible for the improvement in RTFM. [ABSTRACT FROM AUTHOR]