322 to 325 Special Issue on Environmentally Benign Manufacturing and Material Processing Toward Dematerialization

A solid-state recycle processing for magnesium alloy waste has been developed by combining cyclic plastic working and direct hot forging under the short thermal explosion. AZ91D machined chips, which were employed as wasted materials in this study, were consolidated to the green compact with fine microstructures via bulk mechanical alloying (BMA) process, where the compaction and forward extrusion in the closed die were repeated at room temperature. To keep fine microstructures after hot forging, that is, to prevent from the matrix softening due to the grain and/or intermetallic growth, the thermal damage on the green compact in pre-heating before forging was controlled by using the infrared gold image rapid heating furnace. The hot forged AZ91D alloy showed superior mechanical properties such as hardness and ultimate tensile strength (UTS) to the cast one used as input raw materials. The same effects were recognized in the case of wasted Al-Si alloys via this process. The developed solid-state recycle processing revealed a possibility to improve the mechanical properties of the consolidated light alloys even in employing their wasted materials

Corrosion Behavior and Strength of Dissimilar Bonding Material between Ti and Mg Alloys Fabricated by Spark Plasma Sintering

Ti and solution treated Mg alloys such as AZ31B (ST), AZ61 (ST), AZ80 (ST) and AZ91 (ST) were successfully bonded at 475 °C by spark plasma sintering, which is a promising new method in welding field. The formation of Ti3Al intermetallic compound was found to be an important factor in controlling the bonding strength and galvanic corrosion resistance of dissimilar materials. The maximum bonding strength and bonding efficiency at 193 MPa and 96% were obtained from Ti/AZ91 (ST), in which a thick and uniform nano-level Ti3Al layer was observed. This sample also shows the highest galvanic corrosion resistance with a measured galvanic width and depth of 281 and 19 µm, respectively. The corrosion resistance of the matrix on Mg alloy side was controlled by its Al content. AZ91 (ST) exhibited the highest corrosion resistance considered from its corrode surface after corrosion test in Kroll’s etchant. The effect of Al content in Mg alloy on bonding strength and corrosion behavior of Ti/Mg alloy (ST) dissimilar materials is discussed in this work