Influences of Complex Modification of RE and P on the Wear Resistance of Hypereutectic Al-24Si Alloy

Abstract

The influences of RE and P complex modifications on microstructures and wear-resistance of hypereutectic Al-24Si alloy were studied. The results show that the complex modifications of P and RE make the coarse block primary crystal silicon refined and their edges and angles are passivated, the large needle-like network eutectic silicon be modified to the fine lamella or particle ones. The optimum modification effect occurs with 0.10%P and 0.9%RE. The complex modification of P and RE can also obviously improve wear resistance of hypereutectic Al-24Si alloy. When the tested alloys modified with 0.10%P and 0.9%RE, the optimal wear resistance of modified alloys is obtained. The weight loss is decreased to 3.9mg from 5.4mg of the unmodified alloy, decreased by 27.8%. The abrasive wear caused by the breaking of Si phase is dominant wear mechanism of the alloy. It can be attributed to the refinement of primary silicon and eutectic silicon particles and the increase of strength and ductibility of alloys caused by the complex modification of P and RE.

Effect of Cellulose Nanocrystal on Crystallization Behavior of Poly(3–hydroxybutyrate–co–3–hydroxyvalerate)

“…1 (b), it is observed that the nanocomposites exhibited the double melting peaks (T m1 , T m2 ) similar to the neat PHBV in the second heating process, which was caused by melting, recrystallization, and remelting during heating [1,2]. At lower melting temperature the less perfect and lower lamella thickness crystals melted, and then they reorganized to higher perfection and remelted at a higher temperature [2]. The double melting peaks of the nanocomposites were clearer than those of neat PHBV.…”

“…The double melting peaks of the nanocomposites were clearer than those of neat PHBV. The melting point from the higher temperature endothermic peak was taken as the true melting temperature [1,2]. As the CNC contents increased from 0 to 20wt.%, the melting temperature shifted from 130.7 to 168.3 °C, then decreased to 164.8 °C for PHBV/CNC20.…”

“…The CNCs were prepared by hydrolysis of 0.02 g/mL MCC in concentrated sulfuric acid at 50℃ for 1 h, and the highly dispersed CNC suspension in chloroform (81 mg/mL) could be obtained by a solvent exchange procedure as our previous report [2]. Then PHBV was dissolved in the prepared chloroform suspension of CNCs at room temperature.…”

“…Among all kinds of biodegradable polymers, PHBV produced by a wide variety of bacteria as an intracellular reserve of carbon and energy has attracted much attention as an environmentally degradable resin since it has excellent biocompatibility and suitable physical properties. PHBV has more commercial potential applications to replace the petroleum-based synthetic polymers, and also can be used as various biomedical materials [1,2]. However, PHBV still exhibits several shortcomings to restrict its applications, such as slow crystallization rate, brittleness due to its big spherulites, and poor thermal stability [1].…”

“…However, PHBV still exhibits several shortcomings to restrict its applications, such as slow crystallization rate, brittleness due to its big spherulites, and poor thermal stability [1]. In order to improve the rate of crystallization and also decrease the spherulitic sizes of PHBV, the effect of various seeding agents, including the organic and inorganic fillers [1][2][3], on crystallization behaviors, thermal and mechanical properties have been investigated extensively. Recently, more and more attention has been given to the fabrication and the property studies of polymer/CNC nanocomposites due to the high aspect ratio, nanosize in diameter, very low density, and the remarkably enhanced physical properties with a small amount of added CNCs [4][5][6].…”