This work, studied the effect of pulse repetition rate on the micro hardness for each of the surface and cross section by using pulsed ND-YAG laser with laser parameters (Energy = 4.12J).The distance off between the output nozzle and the minimum spot size on the surface of sample was (12mm),and pulse duration was (1.8ms).The results showed that the micro hardness increased after laser treatment ,but the micro hardness decreased with increase pulse repetition rate for both the surface and cross section of the pulses. The micro hardness increased as moving away from the molten zone towards the end of the pulses at the heat affected zone due to increase in cooling rate.
Aluminum alloys are widely used in various industrial applications due to their low weight and favorable mechanical properties. Consequently, extensive research has been conducted to further enhance these properties. In this study, the Al-11%Si alloy was modified by adding varying amounts of antimony (Sb) metal powder: (0.05, 0.1, 0.2, 0.3, and 0.4 wt %), to enhance the mechanical characteristics including the tribological and tensile behavior. The mechanical properties of the modified alloys were thoroughly evaluated. The optimal mechanical performance was achieved with the addition of 0.3% and 0.4% Sb. The casting process involved melting a measured amount of the Al-11%Si alloy at 720 °C in an electric furnace. Antimony powder was then introduced into the melt, which was stirred at 250 r.p.m. for 5 minutes at three stages to form a vortex and ensure uniform dispersion of the modifier. The melt temperature was carefully monitored and controlled using a thermocouple before being poured into a carbon steel mold. Several tests were conducted on the modified alloys, including microstructural analysis, hardness, tensile strength, surface roughness, and wear resistance assessments. The addition of the antimony element (Sb) was found to significantly refine the microstructure and transform the morphology of silicon particles from a flake-like or lamellar form to a more fibrous structure. Furthermore, Sb additions of 0.05%, 0.1%, and 0.2% wt improved micro hardness (Hv), yield strength (YS), and ultimate tensile strength (UTS), while simultaneously reducing surface roughness (Ra) and wear-rate (Wr).
Some mechanical properties of mortar (compressive strength and hardness) with sawdust replacement of sand were investigated. Cubes of 50 mm × 50 mm were prepared, the compressive strength tests were done for a replacement levels ranging (5, 10, 15, 25, 50, 75) % by volume a reference mix were also prepared for comparison this test was done after 7, 14, and 28 days while hardness test were done after 28 day for a replacement levels (0, 5, 10, 15, 25) % by volume. Result showed that the compressive strength of the specimen were decreased with higher sawdust content, hardness values were decreased slightly in the replacement levels 0, 5, 10 % while the values began to decrease noticeably in the replacement levels 15 and 25 % the hardness values were (59, 57.5, 56, 47.77 , 45.2) N/mm2 respectively A cost analysis was done, this analysis was based on a unit of mortar (1.0 m3) made from conventional materials and a modified concrete made by substituting materials with sand using sawdust