Abstract
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.
Highlights
Most pure metals exhibit corrosion resistance [1,2,3], high specific strength [2,4], and good electrical conductivity [2,5] while showing poor mechanical properties [6,7] compared to their alloys
Crater formation was the active deformation mechanism that modified the surface and changed the roughness via the formation of irregular valleys and peaks in the surface profile, similar to the results reported in the literature [4,25,55,56,63]
The modification of surface hardness, roughness, morphology, and cross-sectional microstructure as a function of shot peening (SP) pressure and the cover rate was examined in detail
Summary
Most pure metals exhibit corrosion resistance [1,2,3], high specific strength [2,4], and good electrical conductivity [2,5] while showing poor mechanical properties [6,7] compared to their alloys. Pure Al, including AA1050 Al alloy, has been widely used in various applications such as household items [11], food containers [3], chemical plant equipment [3], light reflectors [3,14], rivets [15], heat exchangers [14], and electrical wiring applications [16] They exhibit high corrosion resistance [17,18] and high thermal and electrical conductivity [2,5,18]. Improving surface and sub-surface hardness of 1xxx Al alloys (AA1050, AA1070, AA1100) is important since their marginal tribological properties associated with their low hardness remarkably restrict their usage in wear-related applications such as architectural flashings, cooking utensils, and rivets [27,28,29,30]
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