Dual heterogeneous structures lead to ultrahigh strength and uniform ductility in a Co-Cr-Ni medium-entropy alloy

Alloys with ultra-high strength and sufficient ductility are highly desired for modern engineering applications but difficult to develop. Here we report that, by a careful controlling alloy composition, thermomechanical process, and microstructural feature, a Co-Cr-Ni-based medium-entropy alloy (MEA) with a dual heterogeneous structure of both matrix and precipitates can be designed to provide an ultra-high tensile strength of 2.2 GPa and uniform elongation of 13% at ambient temperature, properties that are much improved over their counterparts without the heterogeneous structure. Electron microscopy characterizations reveal that the dual heterogeneous structures are composed of a heterogeneous matrix with both coarse grains (10∼30 μm) and ultra-fine grains (0.5∼2 μm), together with heterogeneous L1₂-structured nanoprecipitates ranging from several to hundreds of nanometers. The heterogeneous L1₂ nanoprecipitates are fully coherent with the matrix, minimizing the elastic misfit strain of interfaces, relieving the stress concentration during deformation, and playing an active role in enhanced ductility.

Improving both strength and ductility simultaneously in structural metals and alloys remains a challenge. Here, the authors design a heterogeneous structure in a Co-Cr-Ni alloy that results in ultrahigh strength and significant uniform elongation.

[Intracranial pressure monitoring in clinical practice. Report of 180 cases]

180 severe neurosurgical cases were monitored by intraventricular, epidural and subdural measurements. Intracranial infection rate was 1.1% and the intracranial hypertension rate was 83.3%. Increased intracranial pressure was most often seen in group of head injury. The outcome was poor in cases of uncontrol intracranial hypertension. It was found that intracranial pressure monitoring is useful for diagnosis, treatment and estimation of prognosis and has practical clinical value. This method and indications should be used appropriately according to the different situations. The patients with acute intracranial hypertension should be monitored intensively.