This review paper presents a brief background of a concept for both alloy design and process design in order to enhance properties of pure magnesium applying a combination of mechanical milling (MM) or mechanical alloying (MA) and spark plasma sintering (SPS) process. Powder processing, such as MM, is one of an effective technique for the enhanced properties of the powders. Especially, adding stearic acid as a process control agent (PCA), is significantly effective for not only reducing cold weld, but also strengthening the magnesium matrix during the MM process. MA process is also a powerful technique for synthesising of composite powders. SPS is the advanced consolidation technique for the powders synthesised by the MM/MA processes with relatively shorter sintering time and lower sintering temperature. The properties for two types of developed magnesium materials fabricated by the MM/MA-SPS process with PCA or magnetic powder will be introduced.

The La-Co cosubstituted M-type strontium ferrite attracts attention as a base material for high-performance ferrite magnets. It is known that the uniaxial magnetic anisotropy of the material is enhanced by increasing the amount of Co by heat treatment under high oxygen pressure, but there is a problem in obtaining a pure sample. The present study investigated the conditions to obtain a single phase with increased La-Co substitution by heat treatments under several oxygen pressures. A single phase of M-type ferrite was obtained up to x = 0.35 at p_O2 = 1 atm, and up to x = 0.65 at p_O2 = 10 atm with the composition formula of Sr_1-xLa_xFe_12-xCo_xO₁₉. The magnetic anisotropy is enhanced according to the Co concentration in these samples.

Porous metal materials are constructed using selective laser melting (SLM). Porous metals exhibit different physical and mechanical properties. It is vital to understand how process parameters affect mechanical qualities so that SLM objects can be used in diverse components. In this study, SUS630 specimens were developed under various combinations of laser parameters. The influence of laser power and scanning speed on the tensile strength of porous SUS630 was investigated. Initially, 13 porous specimens were produced under diverse conditions. The tensile tests were performed on these specimens, and their density was evaluated. These results indicated that the energy density affected the tensile strength. In the porous specimens, an experimental equation describing the link between tensile strength and energy density was formulated. Furthermore, the tensile strength in the laminating direction was lower in the porous specimens than in the other orientations.

Fe/MnS composites combined with mechanical and wear-resistance properties were prepared via converge mill (CM) and hot-pressing method, and their mechanical and tribological properties were investigated. CM treated powder consisted of Fe/MnS lamellar structure, Fe and MnS fine-particles by cross-sectional SEM observation. Fe phases in the composite powders after hot pressing bonded to each other and formed a network-like structure. The fraction of the network-like structure in sintered compacts was able to control by the added amount of CM treated powder. As a result of the compressive test and the Vickers hardness test, the ultimate compressive strength and the hardness of sintered compacts increased with increasing the fraction of the network-like structure. In contrast, the wear coefficient didn’t depend on the fraction, and the amount of wear in the wear test decreased with increasing the fraction. These results suggest that the network-like structure was to acts as a reinforcement phase in the self-lubricant material.

本誌第69巻第6号に掲載の加藤大夢氏，松原秀彰氏，寺坂宗太氏，高田真之氏，上高原理暢氏の研究論文「超微粒超硬合金の曲げ破壊の実験と DEMシミュレーション」の下記7点の図につきまして，著者からはカラーの指定を受けておりましたが，誤ってモノクロでの掲載となりました．下記の通り訂正させて頂きます．ご迷惑をお掛けしたことお詫び申し上げます．

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