Research on the microstructure and properties of a multi-pass friction stir processed 6061Al coating for AZ31 Mg alloy

A 6061 Al coating for AZ31 Mg alloy was prepared by multi-pass friction stir welding(FSW)with different travel speeds.The mi-crostructure,mechanical properties of the interfacial region and the corrosion behavior of the coating were investigated systematically.The results indicate that the interfacial intermetallic compounds formed in the stir zone(SZ)consist of mainly Al12Mg17 and Al3Mg2.The inter-metallic compounds in the SZ are significantly increased when the travel speed is increased from 30 mm/min to 60 mm/min.Microhardness measurements and results of shear-tensile tests show that the mechanical properties are influenced by the intermetallic compounds formed in the SZ during FSW.Corrosion tests indicate that the 6061 Al coating can significantly improve the corrosion resistance of AZ31 plate.The 6061 Al coating obtained with a travel speed of 30 mm/min has a maximum corrosion potential E corr of-0.503 V VSE.

Crack behavior in Mg/Al alloy thin sheet during hot compound extrusion

A novel and effective method to co-extrude metallic alloys is described which named Direct Extrusion and Bending-Shear Deformation.The compound extrusion plates have cracked at 290℃ and 3 mm/s.According to this phenomenon,a model was built to investigate the crack generation and development between the 6061 Al and AZ31 Mg alloy during the compound extrusion process by DEFORM-3D.The cracking behavior of the Mg/Al composite rod with a soft Mg AZ31 core and a hard Al 6061 sleeve were systematically studied to disclose the influence of microstructure on crack in the different regions.The simulation results show that the distribution of strain and velocity has significant differences due to the influence of dies structure and material properties at different locations in the same region.The experimental results show that in the same conditions,there are differences in recrystallization and texture weakening of AZ31 Mg alloys and 6061 Al alloy,which are important factors for the formation of crack.Both the Mg layer and the Al layer have a homogeneous microstructure in the region d.

EFFECT OF TOOL WEAR ON MICROSTRUCTURE, MECHANICAL PROPERTIES AND ACOUSTIC EMISSION OF FRICTION STIR WELDED 6061 Al ALLOY

Tool condition is one of the main concerns in friction stir welding （FSW）, because the geometrical condition of the tool pin including size and shape is strongly connected to the microstrueture and mechanical performance of the weld. Tool wear occurs during FSW, especially for welding metal matrix composites with large amounts of abrasive particles, and high melting point materials, which significantly expedite tool wear and deteriorate the mechanical performance of welds. Tools with different pin-wear levels are used to weld 6061 Al alloy, while acoustic emission （AE） sensing, metallographic sectioning, and tensile testing are employed to evaluate the weld quality in various tool wear conditions. Structural characterization shows that the tool wear interferes with the weld quality and accounts for the formation of voids in the nugget zone. Tensile test analysis of samples verifies that both the ultimate tensile strength and the yield strength are adversely affected by the formation of voids in the nugget due to the tool wear. The failure location during tensile test clearly depends on the state of the tool wear, which led to the analysis of the relationships between the structure of the nugget and tool wear. AE signatures recorded during welding reveal that the AE hits concentrate on the higher amplitudes with increasing tool wear. The results show that the AE sensing provides a potentially effective method for the on-line manitoring of tool wear.

On the Selection of a Composite Material for Two-Wheeler Foot Bracket Failure Prevention through Simulation and Mathematical Modeling

A foot bracket is a metal panel bracket used to mount and support the footrest in two-wheeler systems.It holds the footrest in place while rigidly supporting it.In working conditions,this element has often been observed to fail when specific load-fluctuation conditions are established at its rear end.Appropriate materials therefore need to be identified to overcome such a recurring failure.To address these issues,the present study has been implemented with the specific objective to determine the response of selected Al6061-T6 and Al7075-T6 Hybrid Metal Matrix Composites(HMMC).The results,obtained using the ANSYS Software,show that the selected composites can withstand 636,962 N/m^(2)of maximum stress and 8.88×10^(−6)m of minimum displacement.These results are also compared with relevant mathematical models and it is concluded that the identified material combination provides the required improvement of structural stability that can withstand the load fluctuation on the foot bracket.

Superplasticity in an Aluminum Alloy 6061/Al_2O_3p Composite

The superplasticity of an Al203p/6061Al composite, fabricated by powder metallurgy techniques, has been investigated. Instead of any special thermomechanical processing or hot rolling, simple hot extrusion has been employed to obtain a fine grained structure before superplastic testing. Superplastic tensile tests were performed at strain rates ranging from 10-2 to 10-4 s-1 and at temperatures from 833 to 893 K. A maximum elongation of 200% was achieved at a temperature of 853 K and an initial strain rate of 1.67×103 s-1. The highest value obtained for the strain rate sensitivity index (in) was 0.32. Differential scanning calorimeter was used to ascertain the possibility of any partial melting in the vicinity of optimum superplastic temperature. These results suggested that no liquid phase existed where maximum elongation was achieved and deformation took place entirely in the solid state.

Solid-state bonding process induced highly synergistic mechanical properties of 6061 Al alloy joint by shear deformation

Obtaining a highly synergistic mechanical property between joint and base metal(BM)in aluminum(Al)alloy is a chronic problem.In this work,shear bonding technology is applied to a commercial 6061 Al alloy.The results show that a flat and uniform joint interface is obtained.The joint presents a highly synergistic mechanical property compared with BM,whether after shear bonding or heat treatment.The joint coefficient reaches 95.6%after shear bonding and exceeds 100%after heat treatment,which is better than the traditional connection method of aluminum alloy.The high joint coefficient mainly originates from the well-linked joint and gradient grain structure.The gradient grain structure is beneficial to activate more slip systems to coordinate plastic deformation.Although the fine-grained structure is sacrificed after heat treatment,higher strength and joint coefficient are obtained due to the higher work hardening.This newly developed method has a large potential for application to the infinite rolling of Al alloy sheets and can also be used for Al alloy connection in automobile,aerospace,rail transportation,and other fields.The findings in this work can provide essential theoretical support and application reference for the shear connection of Al alloy.