Mechanical properties and wear resistance of medium entropy Fe40Mn40Cr10Co10/TiC composites

The Fe40Mn40Cr10Co10/TiC (volume fraction of TiC, 10%) composites were synthesized in combination of ball milling and spark plasma sintering (SPS) in the present work. Mechanical properties and wear resistance of the Fe40Mn40Cr10Co10/TiC composites were individually investigated. It was found that TiC particles homogenously distributed in the Fe40Mn40Cr10Co10/TiC composite after being sintered at 1373 K for 15 min. Meanwhile, grain refinement was observed in the as-sintered composite. Compared with the pure Fe40Mn40Cr10Co10 medium entropy alloy (MEA) matrix grain, addition of 10% TiC particles resulted in an increase in the compressive strength from 1.571 to 2.174 GPa, and the hardness from HV 320 to HV 872. Wear resistance results demonstrated that the friction coefficient, wear depth and width of the composite decreased in comparison with the Fe40Mn40Cr10Co10 MEA matrix. Excellent mechanical properties and wear resistance could offer the Fe40Mn40Cr10Co10/TiC composite a very promising candidate for engineering applications.

Non-linear Viscoelastic Rheological Properties of PCC/PEG Suspensions

The shear thinning and shear thickening rheological properties of PCC/PEG suspension were investigated with the increase of oscillatory amplitude stress at different constant frequencies. The results show that the complex viscosity was initially independent of stress amplitude and obvious shear thinning occurred, then dramatic shear thickening took place after reaching the minimum viscosity. Typically, in a constant frequency of 5 rad/s, the elastic modulus, viscous modulus, and tanδ （δ is the out-of-phase angle） vs. the stress amplitude was investigated. It is found that the elastic modulus initially appeared to be independent of stress amplitude and then exhibited a rapid decrease, but the viscous modulus was independent of amplitude stress at lower amplitude stress. After reaching the minimum value the viscous modulus showed a rapid increase. On the other hand, tanδ increased from 0.6 to 92, which indicates that the transition from elastic to viscous had taken place and tanδ showed a steep increase when shear thickening occurred. Lissajous plots are shown for the dissipated energy vs. different maximum stress amplitude in the shear thinning and shear thickening regions. The relationship of dissipated energy vs. maximum stress amplitude was determined, which follows a power law. In the shear thinning region the exponent was 1.91, but it steeply increases to 3.97 in the shear thickening region.

Preparation of porous Ta-10%Nb alloy scaffold and its in vitro biocompatibility evaluation using MC3T3-E1 cells

A highly porous Ta-10%Nb alloy was successfully prepared for tissue engineering via the methods of the sponge impregnation and sintering techniques.The porous Ta-10%Nb alloy offers the capability of processing a pore size of 300-600μm,a porosity of(68.0±0.41)%,and open porosity of(93.5±2.6)%.The alloy also shows desirable mechanical properties similar to those of cancellous bone with the elastic modulus and the comprehensive strength of(2.54±0.5)GPa and(83.43±2.5)MPa,respectively.The morphology of the pores in the porous Ta-Nb alloy shows a good interconnected three-dimension(3D)network open cell structure.It is also found that the rat MC3T3-E1 cell can well adhere,grow and proliferate on the porous Ta-Nb alloy.The interaction of the porous alloy on cells is attributed to its desirable pore structure,porosity and the great surface area.The advanced mechanical and biocompatible properties of the porous alloy indicate that this material has promising potential applications in tissue engineering.