The effect of Zn interlayer on the microstructural evolution and mechanical behavior of dissimilar ultrasonic-spot-welded Al/Cu joints was investigated.The tensile lap shear strength in relation to welding energy was ...The effect of Zn interlayer on the microstructural evolution and mechanical behavior of dissimilar ultrasonic-spot-welded Al/Cu joints was investigated.The tensile lap shear strength in relation to welding energy was analyzed.The experimental results show that two intermetallic compounds,Cu5Zn8 and Al2Cu,were generated at the interface of the ultrasonic-spotwelded Al/Cu joint with a Zn interlayer.The primary joining mechanisms of the joint included the intermetallic compound bonding and metallic bonding caused by solid shear plastic deformation.Meanwhile,with increasing welding energy,the plastic deformation of the material became more substantial.With increasing welding energy,the tensile lap shear strength of the joints first increased and then decreased for the ultrasonic-spot-welded Al/Cu joints with and without Zn interlayers.Under the energy input of 700 J,the bearing load capacity of the ultrasonic-spot-welded Al/Cu joints with a Zn interlayer improved signifi cantly due to the observed intermetallic compound(Cu5Zn8).展开更多
The oxide layer on the surface has always been a key obstacle to achieving the diffusion bonding of Al alloys.It is a challenge for performing diffusion bonding without removing oxide layers.Herein,diffusion bonding o...The oxide layer on the surface has always been a key obstacle to achieving the diffusion bonding of Al alloys.It is a challenge for performing diffusion bonding without removing oxide layers.Herein,diffusion bonding of Al alloy retaining continuous oxide layers was successfully achieved in the air by a low-temperature and low-pressure diffusion bonding mothed using a Zn interlayer.During the bonding processes,conducted at 360℃ and 3 MPa,Zn diffused into Al through cracks of thin oxide layers to form the joint composed Al/(diffusion layer)/(oxide layer)/(Zn)/(oxide layer)/(diffusion layer)/Al.The diffusion layers were composed of Zn-Al eutectoid,and the oxide layer included nanocrystals and amorphous Al_(2)O_(3).The shear strength of joints containing continuous oxide layers was about 30 MPa.Interestingly,the migration behavior toward the joint center of the interfacial oxide layers was observed with consuming of the Zn interlayer.The cracking phenomenon,the“subcutaneous diffusion”and the migration behavior of oxide layers were verified and analyzed by the diffusion bonding of anodized 6063Al-6063Al.Subsequently,the dynamic migration mechanism of oxide layers with elements diffusion and bonding interface strengths were discussed in detail.The ability to join Al alloys in the air at low temperatures and low pressure suggests a highly practical and economic method for diffusion bonding.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
基金supported by the National Key R&D Program of China(2018YFB1107900)the National Natural Science Foundation of China and Civil Aviation Administration of China(U1933129)+1 种基金the Natural Science Foundation of Tianjin City(18JCQNJC04100)the National Natural Science Foundation of China(51575383).
文摘The effect of Zn interlayer on the microstructural evolution and mechanical behavior of dissimilar ultrasonic-spot-welded Al/Cu joints was investigated.The tensile lap shear strength in relation to welding energy was analyzed.The experimental results show that two intermetallic compounds,Cu5Zn8 and Al2Cu,were generated at the interface of the ultrasonic-spotwelded Al/Cu joint with a Zn interlayer.The primary joining mechanisms of the joint included the intermetallic compound bonding and metallic bonding caused by solid shear plastic deformation.Meanwhile,with increasing welding energy,the plastic deformation of the material became more substantial.With increasing welding energy,the tensile lap shear strength of the joints first increased and then decreased for the ultrasonic-spot-welded Al/Cu joints with and without Zn interlayers.Under the energy input of 700 J,the bearing load capacity of the ultrasonic-spot-welded Al/Cu joints with a Zn interlayer improved signifi cantly due to the observed intermetallic compound(Cu5Zn8).
基金supported by the National Natural Science Foundation of China under Grant No.51975152.
文摘The oxide layer on the surface has always been a key obstacle to achieving the diffusion bonding of Al alloys.It is a challenge for performing diffusion bonding without removing oxide layers.Herein,diffusion bonding of Al alloy retaining continuous oxide layers was successfully achieved in the air by a low-temperature and low-pressure diffusion bonding mothed using a Zn interlayer.During the bonding processes,conducted at 360℃ and 3 MPa,Zn diffused into Al through cracks of thin oxide layers to form the joint composed Al/(diffusion layer)/(oxide layer)/(Zn)/(oxide layer)/(diffusion layer)/Al.The diffusion layers were composed of Zn-Al eutectoid,and the oxide layer included nanocrystals and amorphous Al_(2)O_(3).The shear strength of joints containing continuous oxide layers was about 30 MPa.Interestingly,the migration behavior toward the joint center of the interfacial oxide layers was observed with consuming of the Zn interlayer.The cracking phenomenon,the“subcutaneous diffusion”and the migration behavior of oxide layers were verified and analyzed by the diffusion bonding of anodized 6063Al-6063Al.Subsequently,the dynamic migration mechanism of oxide layers with elements diffusion and bonding interface strengths were discussed in detail.The ability to join Al alloys in the air at low temperatures and low pressure suggests a highly practical and economic method for diffusion bonding.
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.
