Mechanical Properties and Microstructure Evolution of AA1100 Aluminum Sheet Processed by Accumulative Press Bonding Process

Accumulative press bonding（APB） is a novel variant of severe plastic deformation processes,which is devised to produce materials with ultra-fine grain.In the present work,the mechanical properties and microstructural evolution of AA1100 alloy,which is produced by APB technique,were investigated.The study of the microstructure of AA1100 alloy was performed by optical microscopy.The results revealed that the grain size of the samples decreased to 950 nm after six passes of APB process.The yield strength of AA1100 alloy after six passes of the process increased up to 264 MPa,which is three times higher than that of the as-cast material（89 MPa）.After six passes,microhardness values of AA1100 alloy increased from 38 to 61 HV.Furthermore,the results showed that the behavior of variations in mechanical properties is in accordance with the microstructural changes and it can be justified by using the Hall-Patch equation.Moreover,the rise in the yield strength can be attributed to the reduction in the grain size leading to the strain hardening.

Microstructure and mechanical properties of Mg-5Li-1Al sheets prepared by accumulative roll bonding

Ultrafine-grain and high-strength Mg-SLi-1Al sheets were prepared by accumulative roll bonding （ARB） process. Evolution of microstructure and mechanical properties of ARB-processed Mg-5Li-1Al sheets was investigated. Results show that, during ARB process, the evolution of deformation mechanism oft Mg-5Li-1Al alloy is as follows： twinning deformation, shear deformation, forming macro shear zone, and finally dynamic recrystallization （DRX）. The grain refining mechanism changes from twin DRX to rotation DRX. With the increase in ARB cycles, strength of the Mg-5Li-1Al sheets is enhanced, whilst elongation varies slightly. With the increase in rolling cycles, anisotropy of mechanical properties decreases. It is conclusive that strain hardening and grain refinement dominate the strengthening mechanism of Mg-5Li-1Al alloy.

Detailed Evolution Mechanism of Interfacial Void Morphology in Diffusion Bonding

Similar diffusion bonding of 1Cr11Ni2W2MoV stainless steel was conducted at different bonding tem- peratures. The interface characteristics and mechanical properties of joints were examined, and the evolution of interracial void morphology was analyzed in detail The results showed that there were four typical interfacial void shapes generating sequentially： the large scraggly voids, penny-shaped voids, ellipse voids and rounded voids. The variation of interracial void shape was dominated by surface diffusion, while the reduction of void volume was ascribed to the combined effects of plastic flow of materials around voids, interface diffusion and volume diffusion. Owing to the elimination of void from the bonding interface, the sound joint obtained could exhibit nearly full interracial contact, and present excellent mechanical properties, in which the microhardness and shear strength of joint matched those of base material.