Effect of heat treatment conditions on microstructure and wear behaviour of Al4Cu2Ni2Mg alloy

Al4Cu2Ni2Mg alloy is an age-hardenable aluminum alloy. The effect of different solution and aging heat treatment conditions on the microstructure, hardness and wear resistance of the alloy was studied. The cast specimens were solution treated and then artificially aged. Optical microscopy and scanning electron microscopy were used to investigate the microstructures of the specimens. The hardness and wear tests were applied to understanding the effects of heat treatment. After aging for 8 h, the hardness of the alloy increases from HV₁₀ 96.5 to 151.1. Aging treatment for a longer duration causes a drop in the hardness because of over aging. Increasing the hardness of the alloy increases the wear resistance. As a result of all tests, solution heat treatment at 540 °C for 8 h and aging at 190 °C for 8 h were chosen for optimum heat treatment conditions for this alloy.     

ANTIOXIDANT ACTIVITY AND PHENOLIC ACID CONSTITUENTS OF CHESTNUT (CASTANIA SATIVA MILL.) HONEY AND PROPOLIS

This study describes the constituents of phenolic acids and antioxidant activities of chestnut ( Castania sativa Mill.) honeys and propolis in Turkey. Antioxidant activity of the chestnut honeys and propolis were examined by three different methods, namely scavenging of free radical 2, 2-diphenyl-1-picrylhydrazyl, FRAP, and cupric reducing antioxidant power. Total phenolic contents were determined by using Folin–Ciocalteu reagent as GA equivalent. The phenolic constituents were also determined by HPLC. The antioxidant activities were compared with standard antioxidants such as catechin, BHT and Trolox. The antioxidant activities of all the samples were found high and related to the sample concentrations. The ethanolic propolis extracts showed the highest antioxidant activity. The major phenolic acids of the chestnut honeys and propolis identified by HPLC with PDA detection were coumaric acid, FA, cinnamic acid, CA and ChA.

PRACTICAL APPLICATIONS

In this study, some phenolic acid components and antioxidant capacity of chestnut ( Castania sativa Mill.) honey and propolis were measured. The comparative findings from antioxidant activities and phenolic acid analyses of honey and propolis samples of chestnut origin provide important criteria for considering their nutritional and nutraceutical potentials. Comparison of our results with literature data also ranks the chestnut honey and propolis as better sources of antioxidants among those from other floral origins.     

铜添加对近共晶Al-Si-xCu合金的微观组织和硬度的影响

研究铜含量对Al-Si-xCu（x=2%,3%,4%and5%）合金的微观组织和硬度的影响。不同铜含量的铝合金经熔炼后于690°C铸造成湿砂模并固化,于500°C保温7h进行固溶处理后对样品进行水冷。随后于190°C进行时效处理,分别保温5,10和15h,研究时效时间对基体硬度的影响。采用差热分析法,在冷却速度30K/min下确定平衡相的转变温度,并研究铜含量对四元共晶合金的形成和α（Al）＋Si熔点的影响。结果表明,随着铜含量的增加,发生析出硬化从而导致基体硬度增加,α（Al）＋Si的熔点降低,共晶相的含量增加。当铜含量超过2%时,生成熔点为507°C的四元共晶相。