In the present study, microstructure and porosity of AlSi7Mg0.3 cast alloy including various amounts (0.123; 0.454 and 0.655 wt. %) of iron were investigated. The alloys were produced as secondary (scrap-based -recycled IntroductionAutomotive -chassis, bodies, engine blocks, radiators, hubcaps, and etc. driven by consumer needs and increasingly tight regulations, the automobile industry has made ample recourse to aluminium. A European car today contains on average 100 kg of aluminium, taking advantage of multiple properties of the materials: lightness (a 100 kg loss of weight reduces fuel consumption by 0.6 litres/100 km and greenhouse gases by 20 %), resistance (improved road-handling, absorption of kinetic energy, shorter braking distance) and recycling (95 % of the aluminium contained in autos is collected and recycled, and represents over 50 % of the vehicle's total end-of-life value). Aluminium coming from recycling can allow 95 % energy savings and 85 % less CO 2 emissions compared to primary aluminium production. Recycling -aluminium can be recycled indefinitely without losing any of its intrinsic qualities. This is a considerable advantage in modern metallurgical industry. For the past 20 years the proportion of metal consumed that is recycled has grown steadily and today stands at something like 30 % of primary metal production (European Aluminium Association; Schlesinger, 2014;Hurtalová et al., 2013).The Fig. 1 shows the fraction of world aluminium production from primary and secondary (recycled) sources. About one-third of the aluminium produced in the world is now obtained from secondary sources and in some countries the percentage is much higher. The process used for recycling aluminium scrap is very much different from those used to produce primary metal but in many ways follow the same general sequence. This sequence begins with mining ore, followed by mineral processing and thermal pre-treatment and then a melting step. The metal is then refined, cast into ingots and sent to customers. Aluminium alloys recyclers also face similar challenges to the producers of primary aluminium; there is need to produce a consistent alloy with the required chemistry, reduce the amount of waste generated, minimize energy usage and manufacture the highest-quality product at the lowest possible cost from raw materials of uncertain chemistry and condition (Mc Millan et al., 2012;Schlesinger, 2014).Commercial Al-alloys always contain Fe, often as undesirable impurity and occasionally as a useful minor alloying

It is well known that shot peening is able to increase the fatigue strength and endurance of metal parts, especially with a steep stress gradient due to a notch. This positive effect is mainly put into relation with the ability of this treatment to induce a compressive residual stress state in the surface layer of material and to cause surface work hardening [1]. In this paper shot peening is applied on the 40NiCrMo7 low alloy steel and subsequently the surface was re-peened with glass beads to decrease the final surface roughness. Roughness, hardness and residual stress analysis were used for characterizing the strongly deformed surface layer. Low frequency fatigue tests were carried out to evaluate the effect of the applied treatment on fatigue life in the high cycle region. Results show fatigue strength increase in the high cycle region after the shot peening surface treatment

This work deals with the fatigue resistance of welded joints manufactured from EN S355 J2 structural steel and the possibility of improving fatigue characteristics by the severe shot peening (SSP) surface treatment. Fatigue testing was carried out by the rotating bending test on specimens manufactured from the base material (BM), welded material and welded material treated by SSP. Results have shown big scatter in obtained results from as-welded material and overall reduction of fatigue endurance when compared to the BM. SSP applied on the welded joints has reduced the scatter of experimental data and increased the fatigue strength. Obtained results of fatigue tests are compared, discussed and supported by correlation with results of additional experiments, e.g. metallographic analyses, microhardness tests, residual stresses measurements and surface roughness measurement.

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Fatigue properties of 40NiCrMo7 low alloy steel in the high cycle region were tested by rotating bending fatigue loading (f = 40 Hz, T = 20 5 , R = -1) on notched specimens after application of shot peening surface treatment (cast steel balls with diameter of 0.43 mm, Almen intensity 12A, coverage 100 % and consequently the surface was re-peened with glass beads to decrease the final roughness). The compressive residual stresses created by shot peening increased the time necessary for fatigue crack initiation what in the final case increased fatigue properties. The fatigue limit σc was higher for almost 28 % in the case of notched shot peened specimens.

Abstract. The effect of solution treatment on mechanical properties (UTS, elongation, Brinell hardness) and microstructure (Si-morphology and Si-size) of an aluminium alloy (A356) used for casting cylinder heads was studied. The tests were carried out with specimens machined from the bulkheads of V8 engine blocks cast by the low pressure process. The samples were tested in as-cast and T6 heat treating conditions (solution heat treatment at 530°C with different time -2, 3, 4, 5, 6, 7 hours, quenching in water at 20°C and precipitation hardened for 4 hour at 160°C). The results show that used heat treatment improves mechanical properties of the cylinder head casts. Tensile strength and hardness of specimens increase with solution treatment time. The hardness is a reflection of solution strengthening and silicon particle distribution in matrix. Solution temperature 530°C and 5 hours solution time is appropriate to obtain better morphology and distribution of Si particles in microstructure. Prolonged solution treatment (more than 5 hours) leads to a coarsening of the Si particles, while the numerical Si density decreases. As the particle density decreases, a fewer number of sites are available for crack nucleation, and hence, the fracture properties are improved. The data obtained from this study will be used to improve process control, and to help the selection of heat treatment of the casting for future products.

In materials science, fatigue is the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. If the loads are above a certain threshold, microscopic cracks will begin to form at the stress concentrators such as the surface, persistent slip bands (PSBs), interfaces of constituents in the case of composites, and grain interfaces in the case of metals. Eventually a crack will reach a critical size, the crack will propagate suddenly, and the structure will fracture. The first works about fatigue phenomenon were published since 1837 and intensively was investigated by Wöhler in 1860. With needs of using the progressive materials such titanium and Ni-base superalloys become more significant to put under the various fatigue loading these sorts of alloys. Presented article deals with how the various condition of loading influenced an IN718 alloy fatigue lifetime especially. The fatigue tests provided on this kind of material was done via low frequency loading and push-pull or rotation-bending stress up to this time. Fatigue tests of experimental material was carried out at two different frequencies, 20 kHz with stress ration R = - 1 (push – pull, σm = 0 MPa) as well as the three-point bending load R ˂ 1 (σom = 526.8 MPa) at low frequency 150 Hz at room temperature. The microstructure characterization and Scanning Electron Microscopy (SEM) fractography analysis of fatigue process were done as well. The main goal of study was analyze obtained data after fatigue test and consider, if the various loading modes have influence on fatigue lifetime (initiation sites, crack propagation character, etc.).