EFFECT OF MAGNESIUM ENHANCEMENT ON MECHANICAL PROPERTY AND WEAR BEHAVIOUR OF LM6 ALUMINUM ALLOY
For last several decades aluminium and aluminium alloys are widely used in automotive industries because for their favourable properties like low density (about 2700 Kg/m 3 ), good malleability, high formability, high corrosion resistance and high electrical and thermal conductivity. High machinability and workability of aluminium alloys are prone to porosity due to gases dissolved during melting processes. However, in the engineering application pure aluminium and its alloys still have some problems such as relatively low strength, unstable mechanical properties and low wear resistance. The microstructure can be modified and mechanical properties, wear resistance can be improved by alloying, cold working and heat treatment. In this regards, the present paper reports the influences of enhancement of magnesium contents on the mechanical properties and wear behavior of LM 6 aluminum alloy. Index Terms: LM 6 Aluminum alloy, wear rate 1. Introduction: Aluminium and aluminium alloy are gaining huge industrial significance because of their outstanding combination of mechanical, physical and tribological properties over the base alloys. These properties include high specific strength, high wear and seizure resistance, high stiffness, better elevated temperature strength, controlled thermal expansion coefficient and improved damping capacity (1). These properties obtained through addition of alloying elements, cold working and heat treatment. Alloying elements are selected based on their effects and suitability. For the purpose of understanding their effects and importance, alloying elements for majority of alloys are best classified as major and minor elements, microstructure modifiers or impurities, however the impurity elements in some alloys might be major elements in others (2). LM6 is one of the most important Aluminium alloy falls under Aluminium - Silicon alloying system in which aluminium is the predominant metal and high levels of silicon (4% to 13%) are added that contributes to give good casting characteristics and increases fluidity, by which we can produce castings of thick as well as thin sections according to the required design. Other typical alloying elements are Copper, Magnesium, Manganese, Silicon, Zinc, Iron, Nickel, Lead and Tin.
Investigation of Hardness and Tribological Behaviour of Aluminium Alloy LM30 Reinforced with Silicon Carbide, Boron Carbide and Graphite
The present paper deals with the study of hardness and wear characteristics of SiC (microsize)-, B4C (microsize)- and graphite (microsize)-reinforced aluminium LM30 metal matrix composites (MMC). Matrix alloy with (5, 7 and 13%) of SiC and B4C, and (5, 7 and 10%) of graphite were made using stir casting technique. A pin-on-disc wear testing machine was used to find out the wear rate in which E24 steel disc under dry condition and Brinell hardness testing machine was used to find the hardness of the casted material. This work mainly emphasizes on the investigation of the hardness and wear property of the casted material. The wear properties are tested in both loading and unloading conditions. Wear resistance and hardness of the material are increased when adding the SiC, B4C and graphite. The result shows that properties of stir casting material are good due to the complete dispersion of micropowder.
Experimental investigation of the geotechnical properties and microstructure of lime-stabilized saline soils under freeze-thaw cycling
Abstract The Song-Nen Plain in northeastern China holds one of the three largest expanses of soda saline-alkali soil in the world. Due to its disadvantageous geotechnical properties, the saline soil in this area is unable to meet the needs of construction projects. This study evaluates the stabilizing effect of adding lime to such soils. Specifically, it investigates how the physicochemical and mechanical properties and microstructure of soda saline-alkali soil are altered by lime and how these changes are affected by both freeze-thaw cycling and the duration of curing. The results reveal that adding lime to saline soil transforms clay particles into sand and silt particles and causes the pore size distribution (PSD) to become bimodal, with small-pore and macropore populations. An increase in lime content leads to an increase in the unconfined compressive strength (UCS) but a gradual decrease in both the cation exchange capacity (CEC) and plastic index. Freeze-thaw cycles break up coarse particles and aggregate finer particles, increasing the diameter of macropores and decreasing the USC; however, the effect on specimens with >9% lime is negligible. It is further shown that the geotechnical properties of the soil change immediately after the addition of lime, indicating that the cation exchange reaction takes place very quickly. Furthermore, the pozzolanic reaction leads to an increase in the percentage of sand-sized particles and a decrease in porosity after 28 days of curing. Overall, these results indicate that it is feasible to use lime to improve the engineering properties of soda saline-alkali soil in this area.