Aiming for actual dematerialization, mass flow must be optimized to make full use of the recyclable materials as input and to reduce total amount of wastes. Since the material efficiency is strongly dependent on their adaptivity to the design demand for recycled products, an effective recycling process must accompany the advanced materials processing and manufacturing to improve their original properties to the level above the demand. In the present paper, the light-mass non-ferrous metallic alloys such as aluminum alloys are targeted, to utilize their bulk wastes, which are often ejected from the electric parts or members, as an input material, and to aim for their reuse as an automotive part. Dense, high-strengthened aluminum alloy compact, or, green materials are handled in the present forming and manufacturing up to the final net-shape formation of products by sinter-forging. Selection of reused materials and in-process improvement of their properties are essential keys in this barrier-free processing. Possibility to replace the conventional processing with this barrier-free process lies in: (1) Reduction of in-process energy and mass consumption, (2) Flexibility to yield various kinds of products without any realignment of processes, and (3) Adaptive in-process material modification to design for products in practical use.

Titanium2 mass%Cu and Ti10 mass%Cu alloys were fabricated by powder metallurgy. The alloys were precipitation hardened to observe effect of heat treatment to their wear property. It was found that hardness of the two alloys increased after solution treatment to 320 and 526 HV, and after aging to 441 and 612 HV. However, wear resistance, as characterized by friction coefficient and mass loss in a pin-on-disc wear test deteriorated. In term of wear resistance, a lamellar morphology of eutectoid ¡Ti/Ti 2 Cu was favorable to the homogenized morphology of heat treated alloys. Lowest specific wear rate was found in as-sintered Ti10 mass%Cu, having a value of 1.16 © 10 ¹13 m 3 /N·m.

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.

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This research demonstrated simple but effective process to produce Al-4 mass%Cu/Al 2 O 3 composites, by powder metallurgy method. The starting powders were aluminum, copper, and rice husk ash silica. Processing was by sintering at 650 C for 3.6 ks, hot forging of sintered billet at 600 C under 660 MPa pressure, followed by heat treatment. Hot forging of sintered billet induced plastic deformation of the matrix as well as fractured the porous silica, thus created ultimate contact between the two phases. The following heat treatment produced alumina, which was the reinforcement phase, by chemical reaction between fractured rice husk ash silica and aluminum matrix. The fabricated composite containedand -alumina, and elemental silicon in matrix of aluminum solid solution. Addition of copper facilitated sintering by formation of liquid phase, as well as yielding a matrix material which can be strengthened by precipitation hardening. Maximum hardness obtained was 44 HRA, for composite material using 15 vol% rice hush ash silica. Peak hardness of the matrix was in range of 130-136 HV, after aging for 28.8 to 43.2 ks.