فهرست مطالب sh mirdamadi

The presence of alloying elements, sometimes in a very small amount, affects mechanical properties; one of these elements is Boron. In Aluminum industries, Boron master alloy is widely used as a grain refiner In this research, the production process of Aluminum –Boron master alloy was studied at first; then, it was concurrently added to 2024 Aluminum alloy. After rolling and homogenizing the resulting alloy, the optimal temperature and time of aging were determined during the precipitation hardening heat treatment by controlled quenching (T6C). Then, in order to find the effect of controlled quenching, different cycles of heat treatment including precipitation heat treatment by controlled quenching (T6C) and conventional quenching (T6) were applied on the alloy at the aging temperature of 110°C. Mechanical properties of the resulting alloy were evaluated after aging at optimum temperature of 110°C by performing mechanical tests including hardness and tensile tests. The results of hardness test showed that applying the controlled quenching instead of conventional quenching in precipitation heat treatment caused reduction in the time of reaching the maximum hardness and also increase in hardness rate due to the generated thermo-elastic stresses rather than hydrostatic stresses and increased atomic diffusion coefficient as well. Tensile test results demonstrated that, due to the presence of boride particles in the microstructure of the present alloy, the ultimate tensile strength in the specimens containing Boron additive increased by 3.40% in comparison with the specimens without such an additive and elongation (percentage of relative length increase) which approximately increased by 38.80% due to the role of Boron in the increase of alloy ductility

In this investigation different series of Fe-Cr-C hardfacing alloys with the constant ratio of were fabricated by GTAW on AISI 00 mild steel substrates. OES method was used for determining chemical composition of surface layers while OM, SEM, XRD were used for studying the microstructure and phases characteristics, hardness test (Vickers macro hardness method) was also used to determine hardness of surface layers. The metallographic examination and XRD results indicated that all specimens microstructure consisted of austenite and chromium-iron carbides, (Cr,Fe)7C, moreover by increasing of carbon and chromium content in hardface layers, the volume fraction of (Cr,Fe)7C increased while it caused to decreasing the austenite volume fraction and increasing hardness of the top surface layers. In addition wear Test result Shows that with increasing the chromium and carbon content in hypoeutectic alloys, the wear resistance increase, study of SEM of worn surface determined that wear mechanism of hypo eutectic alloys was micro ploughing, and in eutectic and hyper eutectic were microcutting and micro cracking.