The present study reveals for the first time the dry sliding wear behavior of a powder metallurgical pure titanium alloy (Cp-Ti) modified by shot peening. Cp-Ti samples were manufactured via powder metallurgy, and then their surface and subsurface features were modified using a custom-made, fully automated shot-peening system. The texture isotropy rate and the highest orientation angle of the shot-peened samples were 71.5% and 36°, respectively. The Abbott curves of the shot-peened surfaces revealed that the most common areal roughness value was 5.177 μm, with a frequency of 8.1%. Shot-peened surfaces exhibited an ~20% lower wear rate than unpeened surfaces under dry sliding wear, whereas the coefficient of friction was the same for both surfaces. Micro-ploughing, micro-cutting, oxidation, and three-body abrasion wear mechanisms were observed on the shot-peened and unpeened surfaces. High resolution 3D surface topographies of worn unpeened and shot-peened surfaces revealed micro-scratches and inhomogeneities along wear tracks, which are indicative of three-body abrasion mechanisms during contact. In addition, vertical and horizontal microcracks were visible just beneath the wear track, suggesting a clear indication of plastic deformation during contact. The cross-sectional hardness maps of shot-peened samples revealed the formation of a work-hardened surface layer with shot peening, which improved the wear resistance. These findings support that shot peening can be a useful tool to modify the surface and tribological properties of powder metallurgical Cp-Ti alloys.

AA1050 Al alloy samples were shot-peened using stainless-steel shots at shot peening (SP) pressures of 0.1 and 0.5 MPa and surface cover rates of 100% and 1000% using a custom-designed SP system. The hardness of shot-peened samples was around twice that of unpeened samples. Hardness increased with peening pressure, whereas the higher cover rate did not lead to hardness improvement. Micro-crack formation and embedment of shots occurred by SP, while average surface roughness increased up to 9 µm at the higher peening pressure and cover rate, indicating surface deterioration. The areal coverage of the embedded shots ranged from 1% to 5% depending on the peening parameters, and the number and the mean size of the embedded shots increased at the higher SP pressure and cover rate. As evidenced and discussed through the surface and cross-sectional SEM images, the main deformation mechanisms during SP were schematically described as crater formation, folding, micro-crack formation, and material removal. Overall, shot-peened samples demonstrated improved mechanical properties, whereas sample surface integrity only deteriorated notably during SP at the higher pressure, suggesting that selecting optimal peening parameters is key to the safe use of SP. The implemented methodology can be used to modify similar soft alloys within confined compromises in surface features.

Machining is one of the primary methods used to produce precision machine parts. Machining operations are influenced by many parameters. The most important of these parameters are feed and depth of cut. In addition, as a function of these parameters, many technical characteristics, particularly surface roughness, of the parts produced by machining change. For this reason, it is very important to monitor the machining parameters of the workpieces to be machined and to change them if necessary. Workpieces from many different groups of materials can be machined, but it is more important to monitor and control the machining parameters in stainless steels, which are classified difficult-to-machine materials. In this study, the optimum machining conditions were investigated to obtain the lowest surface roughness values on stainless steel materials (AISI 4462). Two different depths of cut (0.8 mm -1 mm) and three different feeds (0.1 mm/rev - 0.15 mm/rev and 0.20 mm/rev) were used. In addition, for a detailed analysis of the effect of the depth of cut parameter on surface roughness, cutting experiments were performed using three different depths of cut under the best experimental conditions. It was found that the depth of cut, and feed values have a direct effect on the surface roughness. However, it is understood that the feed is highly foremost on the surface roughness and changes the experimental results up to three times.

Tr en Bu çalışmada, yaşlandırılabilir alüminyum alaşım Al-7075-T6 (yaşlandırılmış) malzemenin kaynak edilebilirliği araştırılmıştır. Al-7075-T6 plakalar Al-7075-0 (tavlı/yumuşak) ısıl işlemine tabi tutulmuş ve farklı kaynak parametreleri ile sürtünme karıştırma kaynak yöntemi kullanılarak birleştirilmiştir. Birleştirme sonrası çekme ve eğme deneylerine tabi tutulan parçalar incelenmiştir. Yapılan çalışmalar sonunda düşük devir ve düşük ilerleme hızının daha iyi kaynak çekme dayanımını oluşturduğu görülmüştür. Eğme deneylerinde çekme deneyleri ile karşılaştırıldığında ana malzemeye daha yakın kaynak dayanımı görülmüştür. Bununla birlikte en yüksek çekme dayanımının elde edildiği numunenin eğme dayanımı beklenenin altında gerçekleşmiştir. Bunun nedeni olarak malzeme kaynak alt noktasında bulunan mikro çatlaklar olduğu görülmüştür. In this study, age hardenable material Aluminum alloy Al-7075-T6 (aged) was investigated for weldability. Al-7075-T6 plates were subjected to Al-7075-0 heat treatment and were joined with different welding parameters by means of friction stir welding method. After Joining, the parts which were subjected to tensile and bending tests were examined. As a result of the studies, it was observed that low speed and feed rate generate better tensile strength. When compared with tensile tests, in bending tests, specimen bending strength was observed to be closer to the main material strength. However, the bending strength of the specimen which has the highest tensile strength was lower than expected. It was observed that the reason for this situation is the micro-cracks which were located at the bottom point of the welding material.