Microstructure and Mechanical Behavior of CrFeNi2V0.5Wx(x=0,0.25)High-Entropy Alloys

CrFeNi2V0.5Wx(x=0,0.25)alloys based on these parameters of mixing enthalpy(△Hmix,mixing entropy(△Smix,atomic radius difference(δ),valance electron concentration,and electronegativity difference(△χ)were designed and prepared.The microstructure and room-temperature mechanical behavior of both alloys were investigated.Compressive test results showed that the CrFeNi2V0.5W0.25 alloy had higher yield strength than that of the W-free CrFeNi2V0.5 alloy,although they all exhibited quite larger compressive plasticity(ε>70%).Compression fracture surface of CrFeNi2V0.5W0.25 alloy revealed a ductile fracture in the face-centered cubic(FCC)phase and a brittle-like fracture in theσphase.Moreover,tensile test results indicated that the CrFeNi2V0.5W0.25 alloy exhibited excellent mechanical property with an ultimate tensile strength of 640 MPa and a high tensile elongation of 15.7%.The tensile deformation mode of the FCC phase in the CrFeNi2V0.5W0.25alloy is dominated by planar glide,relating to dislocation configurations,high-density dislocations,and dislocation wall.Therefore,dislocation slip plays a significant role in tensile deformation of CrFeNi2V0.5W0.25 high-entropy alloy.The higher strength of CrFeNi2V0.5W0.25 alloy is predominantly due to the solid solution strengthening of W element andσphase precipitation strengthening.Combination of the higher tensile strength and plasticity suggests that the CrFeNi2V0.5W0.25 alloy can be a promising aerospace material.

Fully Biodegradable Poly(lactic acid)/Poly(propylene carbonate)Shape Memory Materials with Low Recovery Temperature Based on in situ Compatibilization by Dicumyl Peroxide

Fully biodegradable blends with low shape memory recovery temperature were obtained based on poly（lactic acid）（PLA） and poly（propylene carbonate）（PPC）. By virtue of their similar chemical structures, in situ cross-linking reaction initiated by dicumyl peroxide（DCP） between PLA and PPC chains was realized in PLA/PPC blends. Therefore, the compatibility between PLA and PPC was increased, which obviously changed the phase structures and increased the elongation at break of the blends. The compatibilized blends had a recovery performance at 45 °C. Combining the changes of phase structures, the mechanism of the shape memory was discussed. It was demonstrated that in situ compatibilization by dicumyl peroxide was effective to obtain eco-friendly PLA/PPC blends with good mechanical and shape memory properties.