Microstructure Evolution and Mechanical Properties of Mg-Gd-Y-Zn-Zr Alloy Deformed by Multi-Directional Forging with Decreasing Temperature

The multi-directional forging process can achieve large plastic deformation, and has great application prospects in industrial production. The Mg-9.55Gd-3.28Y-1.77Zn-0.34Zr (wt%) alloy containing LPSO phase was deformed in different passes and then quenched immediately by the multi-directional forging process with decreasing temperature, and the microstructure and mechanical properties of the alloy were analyzed. It is found that as the number of deformation passes increases, the coarse grains decrease, and the dynamic recrystallization fraction increases. The dynamic recrystallization grains swallow the original grains, promote the continuous refinement of the grains, and greatly improve the uniformity of the microstructure. At the same time, the maximum texture intensity of the (0001) basal plane is significantly reduced, and the pole figure distribution is more dispersed, which is attributed to the random orientation of dynamic recrystallization. Due to the refinement of the microstructure and the weakening of the texture, the tensile strength and yield strength at room temperature increase significantly. After 3 passes of deformation, the alloy has the highest mechanical properties, with tensile strength, yield strength, and elongation reaching 317 MPa, 233 MPa, and 15%, respectively.

Herbal Extracts Incorporated into Shortbread Cookies: Impact on Color and Fat Quality of the Cookies

This study aimed at determining the effect of aqueous ethanolic extracts from lemon balm, hyssop and nettle, and butylated hydroxyanisole (BHA) on properties of shortbread cookies. This was achieved by instrumental measurements of color and sensory properties of the cookies directly after baking and by determination of peroxide (PV) and p-anisidine (p-AnV) values, and specific extinction coefficients (K232 and K268 values) for fat extracted from the cookies stored for 3 months at room temperature. Increase of the herbal extracts’ concentration from 0.02% to 0.2% in the cookies caused a reduction of L* (the brightness) and a* values (the red coordinate), while b* values (the yellow coordinate) increased when the cookies were enriched with lemon balm and nettle extracts. Among the cookies studied, those prepared with BHA and 0.1 and 0.2% addition of lemon balm extracts were characterized by the highest scores for aroma, taste, and overall acceptability. Incorporation of BHA and 0.02% hyssop extract into the cookies caused a decrease of PV values (the peroxide value) for fat extracted from the cookies after 3 months of their storage compared to a (control) sample without additives and produced the lowest K232 values. Changes in the p-AnV values for the fat samples studied occurred gradually and slowly during the storage and the obtained values were lower compared to the control sample. All of the studied fat samples also showed a higher ability to scavenge DPPH radicals than the control sample. Considering both PV and p-AnV values as indicators of fat oxidation, BHA protected fat extracted from cookies against oxidation better than the herbal extracts used.

Stress State of Turbine Blade Root and Rim Considering Manufacturing Variations

Three-dimensional thermoelastic analysis on the fir-tree root and rim of the I-P cylinder’s first stage blade was performed in two cases of load condition: only centrifugal force and both centrifugal force and temperature load, and five different manufacturing variations were taken into account. The results show that: with high temperature, the stress level of root which is well-designed under room temperature increase obviously, and the load of the four root teeth is unevenly distributed. Moreover, manufacturing variation between contact surfaces lead to serious stress concentration and extremely high stress, and load distribution of the four root teeth is completely uneven. In addition, the influence of temperature on the stress distribution of blade root and rim is much different with different manufacturing variations.

Simulation of TEDREC Phenomena for 4H-SiC Pin Diode with p/n Type Drift Layer

Temperature dependence simulations of forward characteristics for 4H-SiC pin diodes with Shockley-type stacking faults are performed in order to investigate the mechanism of the TEDREC phenomena. The forward voltage drops of both n-type and p-type drift layers at room temperature increase as the length of the Shockley-type stacking fault increases. When the diodes are compared to each other at the same temperature, the differences between the forward voltage drops do not change significantly up to 150 oC, but the differences suddenly narrow in the range from 150 °C to 200 °C. The Shockley-type stacking fault prevents current from flowing at room temperature. The current, however, flows throughout the drifted diode when the temperature is raised.

An X-ray determination of the thermal expansion of α-phase Cu–Si alloys at high temperature

Lattice parameters for four Cu–Si alloys containing 2.2, 4.3, 6.4 and 8.7 at.% Si in the solid-solution range have been calculated in the temperature range 303–928 K. The lattice parameters increase slowly in a nonlinear manner with rise in temperature. The calculated linear thermal-expansion coefficients (α) at room temperature increase with increasing solute concentration (Si) but decrease almost linearly with increasing temperature, the rate of decrease being higher for alloys with higher solute concentration. All the alloys have almost the same average α value (α av ~ 16.0 × 10−6 K−1), which is the value of α at the temperature interval 615–625 K for all the alloy compositions.

Studies of Polymers and of Polymerization. VI. The Vulcanization of Methyl Rubber

Samples of synthetic rubber prepared by the polymerization of dimethylbutadiene at room temperature and at 45° C., respectively, were subjected to vulcanization tests in comparison with natural rubber. In an accelerated gum stock containing 3% sulfur the cold polymer gave at best vulcanized products less than one-third as strong and only about one-third as extensible as natural rubber; the heat polymer gave products as extensible but only one-tenth as strong as natural rubber. The incorporation of carbon black greatly increased the strength of the synthetic rubbers, rendering both about one-half as strong as natural rubber in a similar stock. The vulcanized synthetic rubbers were less “snappy” than natural rubber at room temperature. Increase of temperature improved their speed of retraction, but seriously reduced their breaking strength. Products from the cold polymer showed a greatly increased stiffness and strength at 5° C. as compared with room temperature, and at about 1° C. were non-retractible. In general the synthetic rubbers were much more sensitive than natural rubber to change of temperature. A 50:50 mixture of the heat and cold polymers was also subjected to tests.

STUDIES OF POLYMERS AND OF POLYMERIZATION.: VI. THE VULCANIZATION OF METHYL RUBBER

Samples of synthetic rubber prepared by the polymerization of dimethylbutadiene at room temperature and at 45 °C. respectively were subjected to vulcanization tests in comparison with natural rubber. In an accelerated gum stock containing 3% sulphur the cold polymer gave at best vulcanized products less than one-third as strong and only about one-third as extensible as natural rubber; the heat polymer gave products as extensible but only one-tenth as strong as natural rubber. The incorporation of carbon black greatly increased the strength of the synthetic rubbers, rendering both about half as strong as natural rubber in a similar stock. The vulcanized synthetic rubbers were less "snappy" than natural rubber at room temperature. Increase of temperature improved their speed of retraction, but seriously reduced their breaking strength. Products from the cold polymer showed a greatly increased stiffness and strength at 5 °C. as compared with room temperature, and at about 1 °C. were non-retractible. In general the synthetic rubbers were much more sensitive than natural rubber to change of temperature. A 50:50 mixture of the heat and cold polymers was also subjected to tests.