Interlayer friction stir processing(FSP)has been proved to be an efective method of enhancing the mechanical properties of wire arc-directed energy deposited(WA-DED)samples.However,the original deposition structure wa...Interlayer friction stir processing(FSP)has been proved to be an efective method of enhancing the mechanical properties of wire arc-directed energy deposited(WA-DED)samples.However,the original deposition structure was still retained in the FSP-WA-DED component besides the processed zone(PZ),thus forming a composite structure.Considering the material utilization and practical service process of the deposited component,more attention should be paid on this special composite structure,but the relevant investigation has not been carried out.In this study,an Al–Mg–Sc alloy was prepared by WA-DED with interlayer FSP treatment,and the composite structure was frstly investigated.Almost all of the pores were eliminated under the pressure efect from the tool shoulder.The grains were further refned with an average size of about 1.2μm in the PZ.Though no severe plastic deformation was involved in the retained WA-DED deposition zone,comparable tensile properties with the PZ sample were obtained in the composite structure.Low ultimate tensile strength(UTS)of 289 MPa and elongation of 3.2%were achieved in the WA-DED sample.After interlayer FSP treatment,the UTS and elongation of the PZ samples were signifcantly increased to 443 MPa and 16.3%,while those in the composite structure remained at relatively high levels of 410 MPa and 13.5%,respectively.Meanwhile,a high fatigue strength of 180 and 130 MPa was obtained in the PZ and composite structure samples,which was clearly higher than that of the WA-DED sample(100 MPa).It is concluded that the defects in traditional WA-DED process can be eliminated in the composite structure after interlayer FSP treatment,resulting in enhanced tensile and fatigue properties,which provides an efective method of improving the mechanical properties of the WA-DED sample.展开更多
With the addition of a thin Zn interlayer, 2.4 mm thick Mg-3AI-1Zn alloy sheets were friction stir spot welded （FSSW） using a pinless tool with fiat, convex and concave shoulder shapes. The results showed that an al...With the addition of a thin Zn interlayer, 2.4 mm thick Mg-3AI-1Zn alloy sheets were friction stir spot welded （FSSW） using a pinless tool with fiat, convex and concave shoulder shapes. The results showed that an alloying reaction took place between the Mg substrate and Zn interlayer during FSSW, forming a discontinuous intermetallics layer composed of dispersive （α-Mg ＋ MgZn） eutectic structure under- neath the shoulder and a Mg-Zn intermetallics bonding zone at the outside of the joints. This alloying reaction increased the bonded area and eliminated the hook defects, thereby producing sound FSSWjoints with a shallow keyhole without hook defects. The increase of plunge depth was beneficial to the Mg-Zn diffusion, thereby increasing the tensile-shear load of the joints. However, excessive plunge depths re- sulted in a decrease of the effective sheet thickness, reducing the strength of the joints. At a small plunge depth, the convex and concave shoulders were more beneficial to the interface reaction than the fiat shoul- der. The maximum joint load of 6.6 kN was achieved by using the concave shoulder at a plunge depth of 1.0 mm. A post-welding heat treatment promoted the dissolution of the discontinuous reaction layer in the joints; however, it led to the occurrence of void defects, influencing the bonding strength.展开更多
Al-free ZK60 magnesium (Mg) alloy sheet was selected as substrate material of Mg-steel pinless friction stir spot welding (FSSW), avoiding the effect of the Al element in the substrate on the alloying reaction of Mg-i...Al-free ZK60 magnesium (Mg) alloy sheet was selected as substrate material of Mg-steel pinless friction stir spot welding (FSSW), avoiding the effect of the Al element in the substrate on the alloying reaction of Mg-iron (Fe) interface. The sound FSSW joint of ZK60 Mg alloy and Q235 steel with a hot-dipped aluminum (Al)-containing zinc (Zn) coating was successfully realized. The detailed microstructural examinations proved that Al5Fe2 phase at the Mg-Fe interface came from the pre-existing Al5Fe2 phase in the coating and acted as the transition layer for promoting the metallurgical bonding of Mg and Fe. The interfaces with well-matched lattice sites among Fe, Al5Fe2 and Mg were formed during FSSW. A low energy interface with good match of lattice sites ((002)Al5Fe2//(110)Fe, [110]Al5Fe2//[113]Fe) between Al5Fe2 and Fe was identified. For the interface between Al5Fe2 and Mg, an orientation relationship of (622)Al5Fe2//(3112)Mgand[158]Al5Fe2//[2423]Mg was observed. The tensile-shear load of the ZK60-steel joint could reach 4.6 kN. Moreover, the joint fracture occurred at the interface between the Al5Fe2 layer and the Mg alloy substrate, suggesting the brittle fracture characteristic.展开更多
基金supported by the National Natural Science Foundation of China(No.U23A20538)the Fundamental Research Funds for the Universities of Liaoning Province,Shenyang U40 Outstanding Youth Foundation(No.RC230864)+1 种基金the Foundation of CAS Henan Industrial Technology Innovation&Incubation Center(No.2024110)the Natural Science Foundation of Liaoning Province(No.2023-BS-016)。
文摘Interlayer friction stir processing(FSP)has been proved to be an efective method of enhancing the mechanical properties of wire arc-directed energy deposited(WA-DED)samples.However,the original deposition structure was still retained in the FSP-WA-DED component besides the processed zone(PZ),thus forming a composite structure.Considering the material utilization and practical service process of the deposited component,more attention should be paid on this special composite structure,but the relevant investigation has not been carried out.In this study,an Al–Mg–Sc alloy was prepared by WA-DED with interlayer FSP treatment,and the composite structure was frstly investigated.Almost all of the pores were eliminated under the pressure efect from the tool shoulder.The grains were further refned with an average size of about 1.2μm in the PZ.Though no severe plastic deformation was involved in the retained WA-DED deposition zone,comparable tensile properties with the PZ sample were obtained in the composite structure.Low ultimate tensile strength(UTS)of 289 MPa and elongation of 3.2%were achieved in the WA-DED sample.After interlayer FSP treatment,the UTS and elongation of the PZ samples were signifcantly increased to 443 MPa and 16.3%,while those in the composite structure remained at relatively high levels of 410 MPa and 13.5%,respectively.Meanwhile,a high fatigue strength of 180 and 130 MPa was obtained in the PZ and composite structure samples,which was clearly higher than that of the WA-DED sample(100 MPa).It is concluded that the defects in traditional WA-DED process can be eliminated in the composite structure after interlayer FSP treatment,resulting in enhanced tensile and fatigue properties,which provides an efective method of improving the mechanical properties of the WA-DED sample.
基金supported by the National R&D Program of China under Grant No.2011BAE22B05Liaoning Province Doctor Startup Fund Program No.20131087the National Natural Science Foundation of China under Grant Nos.51371179 and 51331008
文摘With the addition of a thin Zn interlayer, 2.4 mm thick Mg-3AI-1Zn alloy sheets were friction stir spot welded （FSSW） using a pinless tool with fiat, convex and concave shoulder shapes. The results showed that an alloying reaction took place between the Mg substrate and Zn interlayer during FSSW, forming a discontinuous intermetallics layer composed of dispersive （α-Mg ＋ MgZn） eutectic structure under- neath the shoulder and a Mg-Zn intermetallics bonding zone at the outside of the joints. This alloying reaction increased the bonded area and eliminated the hook defects, thereby producing sound FSSWjoints with a shallow keyhole without hook defects. The increase of plunge depth was beneficial to the Mg-Zn diffusion, thereby increasing the tensile-shear load of the joints. However, excessive plunge depths re- sulted in a decrease of the effective sheet thickness, reducing the strength of the joints. At a small plunge depth, the convex and concave shoulders were more beneficial to the interface reaction than the fiat shoul- der. The maximum joint load of 6.6 kN was achieved by using the concave shoulder at a plunge depth of 1.0 mm. A post-welding heat treatment promoted the dissolution of the discontinuous reaction layer in the joints; however, it led to the occurrence of void defects, influencing the bonding strength.
基金This work was supported financially by the National Natural Science Foundation of China(Nos.51601121,51371179 and 51331008)Electron microscopy experiments were carried out at the Center for Microanalysis of Materials at the Frederick Seitz Materials Research Laboratory of University of Illinois at Urbana-Champaign,and supported by Department of Energy Basic Energy Sciences(No.DEFG02-01ER45923)。
文摘Al-free ZK60 magnesium (Mg) alloy sheet was selected as substrate material of Mg-steel pinless friction stir spot welding (FSSW), avoiding the effect of the Al element in the substrate on the alloying reaction of Mg-iron (Fe) interface. The sound FSSW joint of ZK60 Mg alloy and Q235 steel with a hot-dipped aluminum (Al)-containing zinc (Zn) coating was successfully realized. The detailed microstructural examinations proved that Al5Fe2 phase at the Mg-Fe interface came from the pre-existing Al5Fe2 phase in the coating and acted as the transition layer for promoting the metallurgical bonding of Mg and Fe. The interfaces with well-matched lattice sites among Fe, Al5Fe2 and Mg were formed during FSSW. A low energy interface with good match of lattice sites ((002)Al5Fe2//(110)Fe, [110]Al5Fe2//[113]Fe) between Al5Fe2 and Fe was identified. For the interface between Al5Fe2 and Mg, an orientation relationship of (622)Al5Fe2//(3112)Mgand[158]Al5Fe2//[2423]Mg was observed. The tensile-shear load of the ZK60-steel joint could reach 4.6 kN. Moreover, the joint fracture occurred at the interface between the Al5Fe2 layer and the Mg alloy substrate, suggesting the brittle fracture characteristic.
