Effect of Aging Heat Treatment on Bending Strength of -Al2O3 Short Fiber Reinforced LM 13 Aluminum Alloy
AbstractAbstract In this study, -Al2O3 short fibers (0%-30 %) reinforced Al-12Si (wt-%) LM-13 aluminum composites formed by gas pressure infiltration method were used [1]. In the literature the standard aging heat treatment of LM-13 aluminum alloy is given as solutionizing at 515 °C for 8 h. and aging at 171 °C for 12 h. Prior experiments on these composites have shown that this aging treatment was not sufficient to get the intermetallics, that to be precipitated during aging, could not be solved by the standard solution temperatures and times. For example solution treatment at 515°C for 8 hours and then artificially aged at 171°C for 26 hours is the most suitable heat treatment for unreinforced Al-12Si alloy. However optimum heat treatment for 30 pct -Al2O3/ Al-12Si composite the optimum heat treatment was recorded as follows; solution treatment at 535°C for 20 hours and artificial aging at 151°C for 14 hours [2]. Therefore, the aim of this work was to study the effect of -Al2O3 short fibers and aging heat treatment on the bending strength of the LM13 aluminum alloy. Different heat treatment parameters were studied to clarify the effect of the reinforcement on the matrix phase precipitation in these composites. The composites and unreinforced alloy specimens were solution treated at 535 °C temperature for 8, 12, 16 and 20 hours and quenched in water at 20 °C. Aging was carried out at four aging temperatures of 151, 161, 171 and 181°C for a varying time of up to 22 h in air. Unreinforced alloy and the composite samples have subjected to three-point bending tests and the shear strength values were measured. Measurement of bending strength with scanning electron microscopy studies show that the biggest value of bending strength increment for unreinforced and -Al2O3 short fiber reinforced LM13 alloys are very different. The results revealed that at the optimized aging heat treatment conditions have given higher strength results when compared with standard aging treatment. The fracture surface investigations that performed by secondary electron images by scanning electron microscopy (SEM) showed decreased amount of fiber pull-out phenomenon