Dry sliding wear properties of SiC-reinforced AA 2014 aluminium matrix composites produced by vacuum infiltration method were investigated using a pin-on-disc test machine after examining their microstructural and mechanical properties. It was observed that the porosity of the composites decreased with increasing volume ratio up to 2% SiC; above this level, porosity of the composites reached almost constant levels. The hardness of the composites increased continuously with increasing SiC content. It was observed that T7 heat treatment increased the wear resistance and removed the dendritic structure of the produced composites. The highest wear resistance was obtained from AA 2014-2%SiC composite both as-cast and heat-treated conditions. Wear resistance of the composites tested was observed to be strongly dependent on their porosity rather than their other properties.

No abstract

In the current study, an effect of cryogenic treatment on the ageing of a B4C particulate reinforced 7075 aluminium alloy was investigated to identify changes in hardness with respect to ageing time. To achieve this, first, 10, 15, and 25 % by weight B4C particulate containing 7075 Al composite specimens were produced by hot pressing of Al, Cu, Zn, and Mg elemental powders. Next, cryogenic treatment and multiple steps of tempering were adapted to several samples. Such as, after solutionizing at 470• C and sub-zero treatment at -146• C, successive intervals of artificial ageing at 120• C for different time periods were applied. During the heat treatment, hardness values were measured after each interval. Findings reveal that, particularly after solutionization, cryogenic treatment before ageing yields high hardness values. However, the hardness of the composite material exceeds this level during ageing treatment, mainly after long ageing times.K e y w o r d s:

In this study, Al matrix composites consisting of different amounts of Zn, Cu, and Mg were produced using the powder metallurgy technique. In the alloying, powders were ball milled for 120 min via mechanical alloying. After alloying process, the powders were pressed at 800 MPa at room temperature. Sintering (2 h at 600?C in argon atmosphere), solution treatment (2 h at 480?C), and aging processes (3, 6, 9, and 12 h, respectively, at 120?C) were applied to the samples. The hardness and tribo-metallurgy properties of the products were investigated. After sintering, the hardness values of the three alloys were close to each other; however, the solution treatment after sintering caused the hardness values to increase significantly. It was determined that the Al-2Zn-5Cu-4Mg alloy had the highest hardness increase with the 6-h aging heat treatment. The wear resistance of the materials in all the compositions had increased. The highest wear resistance and lowest friction coefficient were obtained for the Al-2Zn-5Cu-4Mg alloy with the 6-h aging heat treatment.

No abstract