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Abstract: Microstructure, mechanical and shape memory properties of homogenized Ti–55Pd–5x (x=Zr/Hf/V/Nb) (at%) ternary alloys were investigated to identify potential alloy systems for functional applications in the temperature range of 400–600°C. The four characteristic temperatures of these alloys were observed to be in the desired temperature range. The yield strengths of martensite and austenite phases were measured to be better than reported for binary Ti–Pd alloys. Two kinds of microstructure developed in these alloys: (i) Ti–55Pd–5Zr and Ti–55Pd–5Hf alloys had B19 martensite as their matrix phase with a significant amount of (Ti, x)2Pd3 and Pd3(Ti, x) (x=Zr or Hf) precipitates; (ii) Ti–55Pd–5V and Ti–55Pd–5Nb alloys had (Ti, x)2Pd3 (x=V or Nb) phase as their major phase along with a small amount of martensite phase. As a result, Ti–55Pd–5Zr and Ti–55Pd–5Hf alloys exhibited significant shape memory; the maximum observed shape memory strain was 1.69% for Ti–55Pd–5Hf alloy. The non-transformable nature of (Ti, x)2Pd3 phase was responsible for the poor shape memory behavior of the other two alloys. [Copyright &y& Elsevier]

Abstract: The trial for quantitative evaluation of inter-granular coupling in stacked perpendicular recording media is reported. The evaluation is realized by analyzing magnetic domain in relation with microstructure of the cap layer initial growth layer. When the thickness of cap layer is increased, the change of magnetic domain from single magnetic domain to maze magnetic domain can be observed. The critical thickness of the cap layer where the change happened was around 5.1nm. According to this analysis, when granular layer and cap layer of stacked media are assumed to be single layer, inter-granular coupling with amount of around 2.9erg/cm2 was obtained which agrees with the simulation result qualitatively. [Copyright &y& Elsevier]

Abstract: Various methods, including focused ion beam (FIB), femto-second laser, KrF eximer laser and dicing techniques, were employed for preparing glassy carbon (GC) micro-molds, and those methods were characterized in terms of the process rate, the roughness and the shape of machined structure. FIB milling using a repetitive pass method produced nano/microstructures with flat channel bottom and nearly vertical sidewalls. Although FIB milling was slowest process, it provided the best quality of machined surface (R a =4–30nm depended on milled depth). Femtosecond-pulsed laser machining also allowed fabricating flat bottom and nearly vertical sidewalls on an area of 1.2×1.2mm2 at a scanning speed of 20mm/s, but lead to an increase of the surface roughness (R a =80nm). Femto-second laser in combination with FIB milling provided a possibility for the rapid fabrication of high quality microstructures on wide surface area. The roughness of machined surface decreased to 45nm by the subsequent FIB milling. Microstructuring with a nanosecond-pulsed KrF eximer laser at an irradiation wavelength of 248nm with a fluence of 13.2J/cm2 also allowed the fast fabrication of master structure for micro-gear, resulted in slanted sidewalls and not ideally flat bottoms. The surface roughness (R a) of the bottom and the side wall was about 45 and 70nm, respectively. Dicing technique allowed machining micro-channels with a rectangular and pyramidal cross-section on an area of 15×15mm2 under the feed speed of 50mm/min. By reducing the feeding speed from 100mm/min to 50mm/min, surface roughness (R a) of the structure side wall decreased from 150nm to 70nm. Achieved glassy carbon molds were then applied to the hot-emboss process of Pyrex and quartz glasses to investigate embossing conditions (emboss temperature, pressure and hold time) needed for the replication of Pyrex and quartz glass structures with various geometries and dimensions in glass plates with thickness of 1mm. Replication results showed good replication at the nanoscale, resulted in the almost the same dimensions and surface roughness with that of cavities. Thicker plate provided faster filling in the emboss process of glass. [Copyright &y& Elsevier]

An investigation has been made of the bond strength of solid-state diffusion-bonded interfaces of tin specimens whose faying surfaces were finished through four different treatments: grinding on abrasive paper of 800 grade, electrolytic polishing in a solution of perchloric acid in ethyl glycol monobutyl and ethanol, halogenation by HCl vapor, and halogenation by HF vapor. The bond strength of the joint was increased with a rise in bonding temperature for all the surface treatments. The grinding on abrasive paper required the highest bonding temperature to obtain the bond strength comparable with the base metal, followed by the electrolytic polishing, halogenation by HCl, and halogenation by HF. These effects of the surface treatments on the bond strength were discussed on the basis of TEM observations of the behavior of interfacial inclusions that were identified as tin oxide and tin oxide halide (for the halogenation treatments) based on SAD and EDX analyses. [Copyright &y& Elsevier]

Effect of Mg content on age-hardening response, tensile properties, and microstructures of a T5-treated thixo-cast Al–7wt.%Si–0.01wt.%Sr alloy has been investigated. The strengths of the T5-treated alloy increase with increasing the Mg content due to the dispersion of high density of needle-like precipitates (β" phases). Also, the addition of 1.0wt.% Mg results in the formation of evenly distributed fine Mg 2 Si phases and Fe-rich compounds in the eutectic Si regions, and therefore, the Al–7wt.%Si–1.0wt.%Mg–0.01wt.%Sr alloy exhibits high 0.2% proof stress of 241 MPa and moderate elongation to failure of 5.1%, which are comparable to those of T6-treated gravity-cast Al–7wt.%Si–0.3wt.%Mg (ASTM A356) alloys. Although the addition of 1.5wt.% Mg or more further improves the strengths, the excess additions of Mg lead to the formation of coarse Mg 2 Si phases. This causes significant loss of ductility, and the alloys show poor elongation to failure of ~2%. [ABSTRACT FROM AUTHOR]

The effect of casting processing and natural aging on microstructures and mechanical properties of T5-treated Al–7wt.%Si–0.5 wt.%Mg–0.01 wt.%Sr (ASTM 357) alloys has been investigated. An artificial aging gives fine precipitation microstructures, and the thixo-cast processing provides much finer distributions of eutectic Si phases and Al 8 Si 6 Mg 3 Fe phases than the gravity-cast and die-cast processing, leading to higher level of strength-ductility balance in the thixo-cast alloys than that of T6-treated Al–Si based cast alloys. Although the prolonged natural aging significantly changes the subsequent artificial age-hardening behaviors and precipitation microstructures, it is interesting to note that the cast alloys could keep their good strengths even after the T5-treatment including the long-term natural aging. This finding will open up the development of strong and ductile cast Al–7wt.%Si–Mg based alloys which can broaden the application of aluminum alloys in automotive industry. • Thixo-casting results in uniform dispersion of fine eutectic compounds. • T5-treatment brings about fine distributions of precipitates. • Thixo-casting and subsequent T5-treatment provide good tensile property. • T5-treated alloys could keep good strengths even after prolonged natural aging. [ABSTRACT FROM AUTHOR]

Highlights: [•] The nickel has a great effect on the microstructures of the weld metals. [•] Grains were rapidly coarsened with increasing Ni content. [•] The nickel has a great effect on content and morphology of retained austenite. [•] The hardness slightly increased with increasing the rotation speed. [•] Results have shown a surprising effect of Ni content on absorbed energy. [ABSTRACT FROM AUTHOR]

The effects of Ge addition on the magnetic properties and microstructure of CoGeCr16Pt8B6 longitudinal thin film media have been examined. CoGe3Cr16Pt8B6 media shows higher coercivity and anisotropy field than CoCr16Pt8B6, despite of lack of Cr segregation at the grain boundary. This implies that CoGeCr-based alloys will be a candidate for next generation material if the Cr segregation can be improved. [Copyright &y& Elsevier]

In the present work, we studied the effect of the aspect ratio of carbon nanotubes (CNTs) on strengthening aluminum metal matrix composites (Al MMCs). To this end, Al samples reinforced with CNTs of various aspect ratios were produced via three different powder metallurgy methods. Microstructural examination revealed that the CNTs were uniformly dispersed in the materials with a range of aspect ratios from 6.5 to 55. The tensile results showed that the CNTs exhibited a strong strengthening effect in the composites regardless of their aspect ratios. However, the post-loading examination and quantitative analysis indicated that there was a strengthening mechanism transition for CNTs, which was closely associated with the aspect ratio or length of CNTs. The origin of such transition was explored from the viewpoint of dislocation-CNTs interaction under loading. The findings may provide a new insight in understanding the strengthening behaviors of CNT-reinforced MMCs. [ABSTRACT FROM AUTHOR]

Strengthening-toughening mechanism of powder metallurgy Ti-Si alloy was investigated by interrupted in-situ tensile tests. The fabricated Ti-Si alloy was strong and ductile. Slip band was blocked mainly by solutes and grain boundaries. Narrow deformed strips, aligned low angle grain boundaries and twin boundaries also played a positive role in this blockage. Cross-slip in the strain hardening stage lowered the difference value of ultimate tensile and yielding strength. Two-stage toughening mechanism was studied (necking onset was demarcation point). In the homogeneous deformation period before necking, strain compatibility was improved by the intergranular rotation (rotation axis along [0001], [-1100] and [-1102]), high-angle intragranular rotation, intergranular sliding and minor twinning deformation. In the heterogeneous deformation period after necking, microcracks initiation/coalescence was dragged by uniform stress distribution. Cracks propagation was also suppressed by dense grain boundaries and front plastic grains. The present comprehensive analysis of strength and toughness provided an in-depth understanding about the relationship among the processing, mechanical properties and microstructure of Ti alloy. [ABSTRACT FROM AUTHOR]

Friction stir welding was performed to accomplish dissimilar lap joining of commercially pure titanium (CP-Ti) to 304 stainless steel (SUS304). The joining speed was varied from 25 to 100 mm min −1 . At a joining speed of 50 mm min −1 , the morphology of the interface was a flat and simple interfacial reaction layer whose thickness was less than 1 μm. The reaction layer consisted of four layers: β-Ti (+ ω-Ti), Ti 2 Ni, FeTi + Fe 2 Ti, and σ-FeCr, listed in order from the CP-Ti side to the SUS304 side. At a joining speed of 25 mm min −1 , the interface consisted of a macroscopically mixed and laminated structure approximately 300 μm thick consisting of multiple reaction layers. During the tensile shear test, joint fractures occurred in the CP-Ti base material at every joining speed. However, during the peel test, joint fractures occurred at the joint interface. [ABSTRACT FROM AUTHOR]

Abstract: In classical models for microstructural evolution, the natural dispersion existing in the samples is often neglected. In this paper, we propose a general procedure that takes into account the distribution of austenite grain size on kinetics of bainite transformation in steels. Through this example and by comparison with experimental data, it is shown that the extended approach provides improved predictions of the overall kinetics. [Copyright &y& Elsevier]