Effects of cold rolling and annealing on the structure of γ″ precipitates in a Ni-18Cr-16Fe-5Nb-3Mo alloy

A Ni-18Cr-16Fe-5Nb-3Mo alloy (a modified alloy 718, referred to herein as 718M), in which the γ″ phase is the only precipitation-strengthening phase, was made by substituting most of the aluminum and titanium in INCONEL 718 with niobium. The specimens of alloy 718M were solid-solution heat treated, aged at 1033 to 1073 K for up to 360 ks, and cold rolled to a reduction of 10 to 15 pct at room temperature. After subsequent annealing heat treatments, at the same temperatures used for aging, the morphological and structural changes of the γ″ precipitates were investigated by transmission electron microscopic observation using carbon extraction replicas. Although stacking faults were not noticed in the γ″ precipitates extracted from the aged 718M alloy, stacking faults introduced in the {112} _γ″ planes by cold rolling of the samples were confirmed. The stripelike contrast due to the stacking faults becomes less clear with increasing annealing time. With longer annealing times, necking occurs between the stripes, which eventually separate into plural particles. The selected-area electron diffraction (SAED) patterns of the cold-rolled and annealed particles show that the metastable γ″ precipitates with stacking faults are transformed gradually into a stable δ phase. In this article, we discuss the basis of morphological and structural changes in detail. INCONEL is a trademark of INCO Alloys International, Inc., Huntington, WV.     

Microstructural evolution and calorimetric evaluation of non-equilibrium states in rapidly solidified Al-Mn-Co ternary alloys

Evolutionary structures were observed in as-melt spun ribbons of Al-3.5Mn-0.8Co, Al-3.5Mn-1.3Co, Al-3.5Mn-2Co, Al-5Mn-0.8Co and Al-5Mn-2Co alloys. The evolutionary structures contained two zones, zone A and zone B, at the chilled and unchilled sides, respectively. A banded structure was observed between the two zones as a transitional region in the Al-3.5Mn-1.3Co alloy. The enthalpy differences, H _O ^ne , between a non-equilibrium state in as-melt spun ribbons and the equilibrium state in fully annealed ribbons of the Al-Mn-Co alloys were evaluated using data obtained by differential scanning calorimetry (DSC) measurements. The values of H _O ^ne for Al-Mn-Co alloys are lower than those for Al-Mn binary alloys. H _O ^ne corresponds to a decrease in Gibbs free energy, G, which is stored in a solidified solid during rapid solidification. The formation of the banded structure is interpreted on the basis of an analysis of the distribution of H _O ^ne or the fluctuation in G, which should oscillate in order to correspond with a gradual reduction of cooling ability for the constrained solidification by the substrate.     

Microstructures and calorimetric evaluation of non-equilibrium states in rapidly solidified Al-Mn alloys containing less than 7 at % Mn

Morphology and enthalpy differences between a non-equilibrium state of as-melt spun ribbons and the equilibrium state of fully annealed ribbons were investigated by TEM observation, X-ray analysis and differential scanning calorimetry (DSC) measurements for Al-1.66, 2.56, 3.95, 5.37 and 6.98 at % Mn alloys. The icosahedral phase was observed with α-Al solid solution in as-melt spun 3.95, 5.37 and 6.98 at % Mn ribbons. The morphology of the icosahedral phase was complex; small particles, petal-like or coral-like branches and eutectic structure within the cell and small particles, films and networks along cell boundaries were observed depending on the manganese content. The differential enthalpy, d(ΔH _o ^ne )/dT, versus T curve obtained by characteristic DSC measurements normally showed three peaks. The peak P₁ at 520–560 K corresponds to the precipitation and growth of the icosahedral phase, the peak P₂ at about 600–800 K to the transformation from the icosahedral phase to the equilibrium Al₆Mn phase, and the peak P₃ at about 700–880 K to the precipitation of Al₆Mn from α-Al solid solution. The temperatures of the peaks P₂ and P₃ shift to the lower side and the height of the peaks becomes higher with increasing manganese content. The enthalpy difference due to the fine microstructure in as-melt spun ribbons was also estimated.     

High-Temperature Scale Formation of Fe–36% Ni Bicrystals in Air

Fe–36% Ni bicrystals were oxidized at temperatures from 1100 to 1250 K in air, both under and without tensile stress. The scales were divided into three categories: external scales, intragranular subscales, and intergranular subscales. A linear relationship exists beween the thickness of scales and subscales and the square root of oxidation time. Tensile stress significantly accelerates intergranular oxidation, but has essentially no influence on either the formation of intragranular subscales or that of external scales. The external scales are composed of -Fe₂O₃ and Fe₃O₄ after a longer oxidation time. The intergranular and intragranular subscales consist of Fe₃O₄ and FeO particles and an Ni-enriched matrix. Cellular or dendritic oxide nodules sometimes exist in the intragranular subscales, causing their frontier interfaces to significantly undulate.     

Humanoid robotics platforms developed in HRP

This paper presents humanoid robotics platform that consists of a humanoid robot and an open architecture software platform developed in METI’s Humanoid Robotics Project (HRP). The final version of the robot, called HRP-2, has 1540 mm height, 58 kg weight and 30 degrees of the freedom. The software platform includes a dynamics simulator and motion controllers of the robot for biped locomotion, falling and getting up motions. The platform has been used to develop various applications and is expected to initiate more humanoid robotics research.     

Information Sharing via Projection Function for Coexistence of Robot and Human

Various kinds of service robots will be used in environment coexisting with humans. To realize the coexistence of a robot and a human, the robot must share task information with the person via an adequate interface. We propose a projection function as the interface for information sharing. We construct a projection system to prove the information sharing efficiency, and develop several modes of interaction between the robot and the human in the projection system.