High-entropy induced a glass-to-glass transition in a metallic glass.

Glass-to-glass transitions are useful for us to understand the glass nature, but it remains difficult to tune the metallic glass into significantly different glass states. Here, we have demonstrated that the high-entropy can enhance the degree of disorder in an equiatomic high-entropy metallic glass NbNiZrTiCo and elevate it to a high-energy glass state. An unusual glass-to-glass phase transition is discovered during heating with an enormous heat release even larger than that of the following crystallization at higher temperatures. Dramatic atomic rearrangement with a short- and medium-range ordering is revealed by in-situ synchrotron X-ray diffraction analyses. This glass-to-glass transition leads to a significant improvement in the modulus, hardness, and thermal stability, all of which could promote their applications. Based on the proposed high-entropy effect, two high-entropy metallic glasses are developed and they show similar glass-to-glass transitions. These findings uncover a high-entropy effect in metallic glasses and create a pathway for tuning the glass states and properties.

Ultrahigh-strength and ductile superlattice alloys with nanoscale disordered interfaces.

Alloys that have high strengths at high temperatures are crucial for a variety of important industries including aerospace. Alloys with ordered superlattice structures are attractive for this purpose but generally suffer from poor ductility and rapid grain coarsening. We discovered that nanoscale disordered interfaces can effectively overcome these problems. Interfacial disordering is driven by multielement cosegregation that creates a distinctive nanolayer between adjacent micrometer-scale superlattice grains. This nanolayer acts as a sustainable ductilizing source, which prevents brittle intergranular fractures by enhancing dislocation mobilities. Our superlattice materials have ultrahigh strengths of 1.6 gigapascals with tensile ductilities of 25% at ambient temperature. Simultaneously, we achieved negligible grain coarsening with exceptional softening resistance at elevated temperatures. Designing similar nanolayers may open a pathway for further optimization of alloy properties.

Amorphophallus konjac anthracnose caused by Colletotrichum siamense in China.

AIMS: Amorphophallus konjac is an important commercial crop grown in China because it is the only plant species which is rich in glucomannan concentration. Recently, an outbreak of anthracnose (incidence ranging from 10-15%) was observed in a field survey conducted from June to August 2018. This study aims to identify the causal agent of A. konjac anthracnose. METHODS AND RESULTS: The pathogen was isolated on potato dextrose agar (PDA) medium. The fungal colony on PDA was greyish to dark grey. Conidia were falcate, one-celled and hyaline. Based on the micro-morphological and cultural characteristics, the pathogen was identified as Colletotrichum sp. blast search and phylogenetic analysis of the ITS, GAPDH, CHS1, ACT, CAL and TUB2 genes revealed the pathogen as Colletotrichum siamense. Koch's postulates were conducted on 2-month konjac leaves with conidial suspension. Development of typical anthracnose disease was recorded 5 days after inoculation and the pathogen's identity was confirmed by re-isolation and molecular identification. CONCLUSIONS: Amorphophallus konjac anthracnose was caused by C. siamense in China. SIGNIFICANCE AND IMPACT OF THE STUDY: Identification of causal agent of A. konjac anthracnose will be helpful in designing effective disease control strategies.

Multicomponent intermetallic nanoparticles and superb mechanical behaviors of complex alloys.

Alloy design based on single-principal-element systems has approached its limit for performance enhancements. A substantial increase in strength up to gigapascal levels typically causes the premature failure of materials with reduced ductility. Here, we report a strategy to break this trade-off by controllably introducing high-density ductile multicomponent intermetallic nanoparticles (MCINPs) in complex alloy systems. Distinct from the intermetallic-induced embrittlement under conventional wisdom, such MCINP-strengthened alloys exhibit superior strengths of 1.5 gigapascals and ductility as high as 50% in tension at ambient temperature. The plastic instability, a major concern for high-strength materials, can be completely eliminated by generating a distinctive multistage work-hardening behavior, resulting from pronounced dislocation activities and deformation-induced microbands. This MCINP strategy offers a paradigm to develop next-generation materials for structural applications.

Group precipitation and age hardening of nanostructured Fe-based alloys with ultra-high strengths.

The precipitation of nanoparticles plays a key role in determining the properties of many structural materials, and the understanding of their formation and stabilization mechanisms has been a long standing interest in the material field. However, the critical issues involving the group precipitation of various nanoparticles and their cooperative hardening mechanism remain elusive in the newly discovered Fe-based alloys with nanostructures. Here we quantitatively elucidate the nucleation mechanism, evolution kinetics and hardening effects of the group-precipitated nanoparticles in the Fe-Cu-Ni-Al-based alloys by atom probe tomography together with both first-principles and thermodynamic calculations. Our results provide the compelling evidence for two interesting but complex group precipitation pathways of nanoparticles, i.e., the Cu-rich and NiAl-based precipitations. The co-existence of the two precipitation pathways plays a key role in age hardening kinetics and ultimately enhances the hardening response, as compared to the single particle type of strengthening, therefore providing an effective new approach for strengthening materials for structural applications.

Enhancing glass-forming ability via frustration of nano-clustering in alloys with a high solvent content.

The glass-forming ability (GFA) of alloys with a high-solvent content such as soft magnetic Fe-based and Al-based alloys is usually limited due to strong formation of the solvent-based solid solution phase. Herein, we report that the GFA of soft magnetic Fe-based alloys (with >70 at.% Fe to ensure large saturation magnetization) could be dramatically improved by doping with only 0.3 at.% Cu which has a positive enthalpy of mixing with Fe. It was found that an appropriate Cu addition could enhance the liquid phase stability and crystallization resistance by destabilizing the α-Fe nano-clusters due to the necessity to redistribute the Cu atoms. However, excessive Cu doping would stimulate nucleation of the α-Fe nano-clusters due to the repulsive nature between the Fe and Cu atoms, thus deteriorating the GFA. Our findings provide new insights into understanding of glass formation in general.