This work investigates the influence of geometry on the behaviour of a commercial diffusion bonded low alloy steel powder (added by 0.65% graphite and 0.6% lubricant) during uniaxial cold compaction. Cylindrical specimens and ring-shaped specimens were produced, characterized by different geometrical parameters. The whole analysis has been performed using experimental data, the forces and displacements continuously recorded by an industrial press without any additional device, aiming at obtaining results representing the actual conditions in the production of real parts. The stress field acting on the powder column was derived from the recorded data, obtained from two different compaction strategies. By single action cold compaction experiments the parameters characteristics of the powder mix were derived, such as the radial stress transmission coefficient, the flow stress, the friction coefficient with the die walls, and the friction coefficient with the core in case of rings. These results were used investigating the powder behaviour during double action cold compaction, which represents the most common compaction strategy. Densification curves were derived from this analysis, reporting the relative density as a function of both the applied and the mean axial stress. The influence of the geometry on the densification was highlighted and discussed.

In order to improve the controllability of the mechanical properties of powder metallurgy (PM) titanium (Ti) -nickel (Ni) super-elastic alloys, cobalt (Co) powder was added to the alloys up to 2.0 at.%. In particular, the dependence of plateau stress and recovery rate in tensile hysteresis test on Co content was investigated by considering microstructures analysis results. XRD and TEM-EDS analysis clarified Co elements existed as substitutional solution atoms in Ni atom sites of Ti-Ni alloys. It was confirmed that PM Ti-Ni-Co alloys with the Co content of 1.0 at.% Co or less showed a high shape recovery rate of around 90% or more. In addition, the increment of the plateau stress of Ti-Ni-Co alloys was almost constant regardless of the holding time in heat treatment. That is, the Co solution content had no effect on the amount and morphological size of Ti₃Ni₄ precipitates. Therefore, it was possible to independently control the plateau stress without affecting sliding critical strain by adding Co element to Ti-Ni alloys.

High temperature strength is one of the critical technical issues to apply metal injection molding (MIM) to Nickel-based superalloy IN713. In this study, through investigating microstructure and high temperature strength of IN713-MIM materials in detail, we developed the technique to promote grain growth. In the experiments using IN713C-MIM materials, the high temperature tensile strength and the creep strength were remarkably inferior to the castings. The creep deformation mechanism of IN713C-MIM materials is revealed that grain boundary diffusion creep was dominant as the stress exponent was determined as n = 2.72. Therefore, we found out that it was important to reduce the amount of grain boundary by promoting grain growth. In the examinations aiming to reduce carbides on grain boundary, which inhibited grain boundary migration, the carbon content of IN713LC-MIM-sintered material could be suppressed to C = 0.05%. Subsequently, when IN713LC-MIM-HIP-ed material was subjected to additional heat treatment at 1280°C for 12 hr, significant grain growth was observed.

HIP is a technology to simultaneously apply high pressures and temperatures to processed products by gas. HIP equipment applying HIP technology is used as an indispensable technology for densification of sintered products, removal of pores in casting and diffusion bonding of dissimilar materials.

In this article, we will explain the history of the development of HIP equipment in Japan, then the introduction of new technology of the rapid cooling method and the HIP equipment with enhanced gas recovery capacity, aiming at productivity improvements of the HIP process, both of which were newly developed by our company.

In this study, we investigated the effects of hot isostatic pressing (HIP) on the mechanical properties of an Al-10%Si-0.4%Mg alloy fabricated by selective laser melting (SLM). In addition, the effect of internal porosity on the mechanical properties of the alloy was also investigated. After the HIP, the internal porosity of the alloy decreased, while its elongation to failure (EL) improved significantly. However, the 0.2% proof stress (PS) and the tensile strength (TS) of the HIPed alloy were significantly lower than those of the as-built state. This can be attributed to the microstructural changes that occurred at elevated temperatures during the HIP. In addition, the PS and TS of the as-built alloy decreased with an increase in the internal porosity. On the other hand, in the case of the HIPed alloy, the PS and TS were not affected by the internal porosity. However, EL was sensitive to the internal porosity. The EL of the HIPed alloy decreased with an increase in its initial internal porosity. This is because the diffusion bonding during the HIP was imperfect owing to the presence of oxidized scales. Hence, it is imperative to optimize the laser irradiation conditions for the fabrication of aluminum alloy by SLM.

Diamond/SiC = 75/25~50/50 vol% composites were fabricated utilizing liquid-phase reaction sintering during hot isostatic pressing (HIP) at 1723 K under 196 MPa for 7.2 × 10³ s from mixtures of four kinds of diamond (average particle size P_s of 69, 60, 9.2, and 3.5 μmϕ) and Si (P_s: 0.6 μmϕ) powders. After the starting powders were mixed for 1.8 × 10³ s in ethanol, the mixtures were dried and compacted uniaxially (50 MPa) and isostatically (245 MPa). They were preheated at 1223 K for 7.2 × 10³ s in a vacuum (Process (I)) or solidified using pulsed electric-current pressure sintering (PECPS) at 1623 K and 50 MPa for 0.6 × 10³ s under reduced pressure (Process (II)). The compacts prepared via Process (I) and Process (II) were densified by Pyrex glass capsule HIPing (1723 K/7.2 × 10³ s/196 MPa/Ar). High relative density (around 93%) was achieved at the composition of diamond/SiC = 55/45 vol% using bimodal diamond powders, i.e., an average P_s of around 50 μmϕ and Process (II). In order to improve Vickers hardness (H_v), a small amount of B₄C (P_s: 0.5 μmϕ) powders was added to [diamond (69:3.5 μmϕ = 7:3)]/SiC = 55/45 vol% composite using Process (II) at 1623 K followed by HIP. Both the relative density and H_v values increased substantially, from 89 to 95.0% and from 38.7 to 51.3 GPa at 10 vol% B₄C addition, respectively.

本誌第65巻第7号に掲載の刈屋　翔太氏，福生　瑞希氏，梅田　純子氏，近藤　勝義氏の研究論文「純チタン焼結材における軽元素固溶強化に関する実験データを用いたLabuschモデルによる定量解析」につきまして，著者より訂正の申し出がありました．訂正箇所は下記の通りです．

◆P. 411右段9行目

（正） (5)

（誤） (5)

◆P. 411右段17行目～19行目

（正）しかしながら，(5)式に着目すると，変数部は固溶原子量に係るcを含むc^2/3/S_Fであり，定数部は(F_m⁴w/4Gb⁹)^1/3である．

（誤）しかしながら，(5)式に着目すると，変数部は固溶原子量に係るcを含むc^2/3/S_Fであり，定数部は(F_m⁴w/4Gb)^1/3である．

◆P. 411右段29行目～32行目

（正）そこで，定数部(F_m⁴w/4Gb⁹)^1/3を算出した結果，4.17 × 10³となり，この値に基づいてF_m値を算出したところ，6.22 × 10⁻¹⁰が得られた．

（誤）そこで，定数部(F_m⁴w/4Gb)^1/3を算出した結果，4.17 × 10³となり，この値に基づいてF_m値を算出したところ，6.22 × 10⁻¹⁰が得られた．

◆P. 411右段41行目～43行目

（正）その際の定数部(F_m⁴w/4Gb⁹)^1/3の値は3.29 × 10³となり，これを用いてF_mを算出した結果，5.21 × 10⁻¹⁰が得られた．

（誤）その際の定数部(F_m⁴w/4Gb)^1/3の値は3.29 × 10³となり，これを用いてF_mを算出した結果，5.21 × 10⁻¹⁰が得られた．