Aging Treatment Process Research Articles

Strengthening study on 6082 Al alloy after combination of aging treatment and ECAP process

Equal channel angular pressing (ECAP) was used before and after various aging treatments in order to strengthen a commercial 6082 Al alloy. Experiments were carried out to study the strengthening of the alloy due to pre and post-ECAP aging treatment. It was found that aging before and after ECAP processing is an effective method for strengthening of the alloy. An increase in both strength and ductility of the ECAPed specimen was achieved via appropriate post-aging treatment. This was in such a manner that for maximal strengthening, post-ECAP aging is best conducted at temperatures lower than those usually used for aging if prior work hardening is not undertaken. Pre-ECAP aging was also discussed in the light of dislocation density and work hardening.

On-Line Aging to Improve the Tensile Strength and Conductivity of Cold-Drawing AA6201 Wires

AA6201 with main compositions of Mg-0.5 wt % and Si-0.5 wt %, is a typical electric conductive alloy which shows remarkable combination of high strength and high electric conductivity after heat treatment. Cold working and aging treatment process have a significant effect on its mechanical properties and conductivity. Shearing/Cooling Rolling process (SCR) was proposed to produce the feedstock for all aluminum alloy conductor. The effects of cold drawing on the properties of the alloy produced by SCR process were investigated. There are two methods used in the study, one is the cold drawing and aging heat treatment (CDAH) to produce the wires, the feedstock prepared by SCR and on-line solution, the other is the feedstock prepared by SCR and on-line solution-aging heat treatment plus cold drawing (AHCD). Results show that the AHCD can improve the properties of products due to sub-structural hardening. The tensile strength and equivalent conductivity of the alloy are 315 MPa and 55.03 % IACS respectively, and are much better than those characteristics of the alloy produced by the conventional process (295 MPa, 52.5-53.0 % IACS).

Fabrication and electrical sliding wear of graphitic Cu–Cr–Zr matrix composites

Abstract The present work was undertaken to prepare graphitic Cu–Cr–Zr matrix composites in order to develop new materials for application under sliding contact in an electrical field. The electrical sliding wear behavior of the graphite (Gr)/CuCrZr composite was investigated from a microstructural viewpoint, compared with the matrix alloy. The results indicate that by using the water atomized Cu–Cr–Zr powder and copper-coated graphite particles as starting materials, compact and homogeneous microstructure can be obtained in the composites. Fine and coherent particulate precipitations are formed in the Cu–Cr–Zr matrix during the aging treatment process, which help to improve the mechanical properties. Under the electrical sliding wear condition, incorporation of graphite in the Cu–Cr–Zr matrix not only decrease the wear loss of the sliding pair but also maintain steady-state friction coefficient. The main reason is that the graphite film that smears on the contacting surfaces can alleviate materials loss induced by electric arc discharge and adhesion wear. Proper aging treatment helps to make full use of the solid lubricant effect of the graphite particles.

Microstructure and fatigue characteristics of direct chill cast and electromagnetic cast 2024 Al alloy ingots

The distinct advantages of the electromagnetic casting (EMC) process consist in the presence of stirring motions in the melt, which lead to significant grain size reduction in solidified ingot. Furthermore, surface and subsurface qualities are improved due to the absence of ingot mold. However, it is impossible to achieve the aforementioned advantages in conventional direct chill casting (DCC). In order to contrast the before and after heat treatments of the microstructural and mechanical characteristics of EMC and DCC 2024 aluminium alloys, optical microscopy, scanning electron microscopy, transmission electron microscopy (TEM), X-ray diffractions (XRD), differential scanning calorimetry (DSC), etc. were carried out. Compared with the DCC ingot, the EMC ingot has better mechanical properties not only in the ascast condition but also in the as-aged condition. The DSC curves show that the EMC specimens have high enthalpy, i.e., the thermal kinetic energy to form precipitates during the aging treatment process. Despite heat treatments applied to the DCC ingot, it fails to attain the same mechanical properties as the EMC ingot. Moreover, considering the expernsive scalping operation for DCC ingots, the EMC technique, which offers a lower manufacturing cost, is one of the best manufacturing methods used in obtaining the ingots of wrought aluminum alloys.