Effect of heat treatment on impact resistance of AU5GT and AS7G06 aluminum alloys

Impact strength is one of the major mechanical properties that a material should possess in order to absorb sudden changes in the load intensity. The objective of current study is to compare the impact strength of two material (AU5GT and AS7G06), which are used in different structural applications. Almost no work is available which compares the impact strength of selected grade alloys along with different heat treatment cycles. Specimens are heat treated first as per designed cycles, later impact testing is performed. Charpy impact test is conducted in accordance with ASTM E23-12 standard method on three samples with and without heat treatment for each cycle. Solutionizing on samples is done at constant time and temperature to achieve homogenization. Later, aging is conducted at different temperatures ranging from 100-200°C (different intervals) at constant time to find the effect of precipitation hardness that actually increases the strength. Sample hardness is determined using Vickers micro hardness testing machine for each heat treatment cycle. Charpy test results provided the impact energy that is used to determine the strength before fracture. Heat treated samples have showed increase in impact strength for AS7G06 aluminum alloy while AU5GT shows very little change. This is because of growing the precipitation with respect to temperature, which resulted in more hard regions across grains. Hardness also shows an increasing relationship, as expected. Fracture surfaces are analyzed on stereo microscopy and Scanning electron microscopy (SEM) to find the final mode of fracture, that is brittle, ductile or transitional (combination of both brittle and ductile).