Elemental partitioning-mediated crystalline-to-amorphous phase transformation under quasi-static deformation.

The transformation induced plasticity phenomenon occurs when one phase transforms to another one during plastic deformation, which is usually diffusionless. Here we present elemental partitioning-mediated crystalline-to-amorphous phase transformation during quasi-static plastic deformation, in an alloy in form of a Cr-Ni-Co (crystalline)/Zr-Ti-Nb-Hf-Ni-Co (amorphous) nanolaminated composite, where the constitute elements of the two phases have large negative mixing enthalpy. Upon plastic deformation, atomic intermixing occurs between adjacent amorphous and crystalline phases due to extensive rearrangement of atoms at the interfaces. The large negative mixing enthalpy among the constituent elements promotes amorphous phase transformation of the original crystalline phase, which shows different composition and short-range-order structure compared with the other amorphous phase. The reduced size of the crystalline phase shortens mean-free-path of dislocations, facilitating strain hardening. The enthalpy-guided alloy design based on crystalline-to-amorphous phase transformation opens up an avenue for the development of crystal-glass composite alloys with ultrahigh strength and large plasticity.

Safety, tolerability, and immunogenicity of a CpG/Alum adjuvanted SARS-CoV-2 recombinant protein vaccine (ZR202-CoV) in healthy adults: Preliminary report of a phase 1, randomized, double-blind, placebo-controlled, dose-escalation trial.

This was a phase 1 dose-escalation study of ZR202-CoV, a recombinant protein vaccine candidate containing a pre-fusion format of the spike (S)-protein (S-trimer) combined with the dual-adjuvant system of Alum/CpG. A total of 230 participants were screened and 72 healthy adults aged 18-59 years were enrolled and randomized to receive two doses at a 28-day interval of three different ZR202-CoV formulations or normal saline. We assessed the safety for 28 days after each vaccination and collected blood samples for immunogenicity evaluation. All formulations of ZR202-CoV were well-tolerated, with no observed solicited adverse events ≥ Grade 3 within 7 days after vaccination. No unsolicited adverse events ≥ Grade 3, or serious adverse events related to vaccination occurred as determined by the investigator. After the first dose, detectable immune responses were observed in all subjects. All subjects that received ZR202-CoV seroconverted at 14 days after the second dose by S-binding IgG antibody, pseudovirus and live-virus based neutralizing antibody assays. S-binding response (GMCs: 2708.7 ~ 4050.0 BAU/mL) and neutralizing activity by pseudovirus (GMCs: 363.1 ~ 627.0 IU/mL) and live virus SARS-CoV-2 (GMT: 101.7 ~ 175.0) peaked at 14 days after the second dose of ZR202-CoV. The magnitudes of immune responses compared favorably with COVID-19 vaccines with reported protective efficacy.

Substantially enhanced homogeneous plastic flow in hierarchically nanodomained amorphous alloys.

To alleviate the mechanical instability of major shear bands in metallic glasses at room temperature, topologically heterogeneous structures were introduced to encourage the multiplication of mild shear bands. Different from the former attention on topological structures, here we present a compositional design approach to build nanoscale chemical heterogeneity to enhance homogeneous plastic flow upon both compression and tension. The idea is realized in a Ti-Zr-Nb-Si-XX/Mg-Zn-Ca-YY hierarchically nanodomained amorphous alloy, where XX and YY denote other elements. The alloy shows ~2% elastic strain and undergoes highly homogeneous plastic flow of ~40% strain (with strain hardening) in compression, surpassing those of mono- and hetero-structured metallic glasses. Furthermore, dynamic atomic intermixing occurs between the nanodomains during plastic flow, preventing possible interface failure. Our design of chemically distinct nanodomains and the dynamic atomic intermixing at the interface opens up an avenue for the development of amorphous materials with ultrahigh strength and large plasticity.