Influence of Al content on machinability of AM series magnesium alloys

Abstract

This study investigates the effects of Al (aluminium) amount in AM series magnesium alloys on mechanical properties and machinability (cutting forces). Changes in microstructure and mechanical properties and their effects on cutting forces were analysed depending on the increase in Al amount. For this reason, AM series magnesium alloys (AM20, AM40, AM60, and AM90) with varying amounts of Al % (from 2 to 9 %) were used in the study. It was observed that in AM series magnesium alloys (containing 0.5 % Mn), intermetallic phases found in microstructure (Mg17Al12 and Al8Mn5) improved the mechanical properties and lowered machinability by rising the cutting forces (Fc) depending on the increase in Al amount. Also, the surface roughness (Ra) of intermetallic phases was observed to have an impact on flank build-up-FBU and chip formation. While AM90 had the highest values in terms of mechanical properties and surface quality, AM20 had the lowest values. On the other hand, AM20 had the highest El% values and machinability properties.

A Comparative Study on Wear and Machinability Behaviors of AM20, AJ21 and AS21 Magnesium Alloys

“…In this study, Mg alloys used were first melted in atmosphere controlled melting furnaces (under CO2+SF6), and then cast into metal moulds. Ünal [10,16] and Akyüz [6,13,15] described the casting or manufacturing process of these magnesium alloys in their previous studies. In the previous studies of the author describe the details for the procedures as well as the sample standards for the test (namely the polishing, etching solutions & etching process, machining tests and tensile tests of the microstructure samples) [5,8].…”

“…From this point, it can be said that intermetallic phases have an effect on the magnitude of cutting forces and surface roughness of the alloys. According to the study, it can be said that the increase in cutting forces due to the change in alloy composition and the increase in cutting speed causes dislocation deposit in the chip and cutting tip interface, resulting in an increase in the cutting forces [5,7,13,15,19,[25][26][27][28][29][30][31][32]. In AJ21, it can be said that the higher cutting forces have a larger effect in increasing the cutting forces of the Al4Sr intermetallic phase, thereby reducing the machinability of the alloy.…”

“…During the processing of the experiment samples, as a result of the effect of the alloy compositions and cutting parameters, it may be argued that FBU and wear occur at the cutting tool tip due to the dry adhesion and temperature rise between the cutter and the sample surface. It is known from the literature that there is a temperature increase at the cutting tool tip as a result of not using coolant during machining owing to the combustion of Mg alloys and the effect of dry adhesion [5][6][7][8][9][10][11][12][13][14][15][25][26][27][28][29][30][31][32]. In addition, it has been reported in the previous studies that dislocation deposit on the cutting surface caused by dry adhesion on the cutting tool tip increases the cutting forces in the machining of magnesium alloys [6,8,13,15].…”

“…It is known from the literature that there is a temperature increase at the cutting tool tip as a result of not using coolant during machining owing to the combustion of Mg alloys and the effect of dry adhesion [5][6][7][8][9][10][11][12][13][14][15][25][26][27][28][29][30][31][32]. In addition, it has been reported in the previous studies that dislocation deposit on the cutting surface caused by dry adhesion on the cutting tool tip increases the cutting forces in the machining of magnesium alloys [6,8,13,15]. According to the results of this study, it can be concluded that the intermetallic phases (Al8Mn4 in AM20, Al4Sr in AJ21 and Mg2Si in AS21) that started to form in the microstructure of magnesium alloys have an effect on the magnitude of cutting forces, surface quality, FBU as well as wear on the cutting tool tip and the chip morphology (Figures 7-9).…”

“…Automotive, transport, aerospace and electronics sectors may be mentioned among the most important of these [1][2][3][4][5][6][7]. Having properties such as low density, high strength, high wear and creep resistance, as well as being among the lightest building metals, having mechanical properties can be improved and being castable, these alloys have important features that enable them to find new areas of use every day [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. Because of their light weight (low density), magnesium alloys play an important role in achieving fuel economy and emissions (CO2, SOX, and NOX vb.)…”