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Although Ti2AX has excellent mechanical properties of both metals and ceramics, there are few papers exploring the correlation between mechanics and thermodynamics simultaneously. In this paper, the structure properties, elastic anisotropies, thermodynamic and tensile properties of Ti2AX (A = Al and Ga, X = C and N) MAX phases are studied by first-principles calculations. The results show that these MAX phases have thermodynamical, dynamical, and mechanical stabilities. The calculated anisotropy indexes indicate that the MAX phases are anisotropic in elastic modulus. Ti-X chemical bonds possess covalent-ionic mixed nature. Moreover, the sound velocities and thermal conductivities of these Ti2AX MAX phases are also anisotropic. According to the tensile calculation, the tensile strength along the [110] direction is greater than that along the [001] direction, and fracture failure will occur in the [110] direction. [ABSTRACT FROM AUTHOR]

The concentrations of Cu, Fe, Mn, Ni, Zn, Cr, Pb, and Cd in 37 samples collected from surface sediments from the Inner Mongolia section of Yellow River, China were discussed in order to estimate their distribution and pollution level. The measured metals in the sediments were found be in the range of Cu 10.28~45.54, Fe 18, 460.00~41, 880.00, Mn 448.90~919.83, Ni 8.52~67.39, Zn 60.93~149.40, Cr 65.69~149.67, Pb 0.50~19.98 and Cd 0.23~4.36 mg kg–1. The mean values of the heavy metal contents were arranged in the following decreasing order: Fe > Mn > Cr > Zn > Ni > Cu > Pb >Cd. Significant positive correlations were observed between the concentrations of Cu, Fe, Mn and Zn. Common sources and the identical behavior are observed in these heavy metals. PCA extracted two components with eigenvalues explaining 62.190% of the total variance. Cu, Fe, Mn, Zn, Cr had the natural origin controlled by the first factor. Anthropogenic causes are major sources of Pb and Cd. Ni could be affected by natural geological background and human activity. The higher values of Geo-accumulation index, enrichment factor, and PLI of Cr were attributed principally to anthropogenic activities. Fe and Zn did not lead to pollution. The Sediment contamination grade from the Inner Mongolia section in upstream of Yellow River was 0~1, belonging to from unpolluted to moderately polluted. [ABSTRACT FROM AUTHOR]

In this work, a Mg–Zn–Ca magnesium matrix nanocomposite containing nano-sized TiC particles was firstly processed by multidirectional forging (MDF). With increasing the forging temperature from 230 to 310 °C for 1 MDF pass or the number of MDF passes at 270 °C, both volume fractions and average sizes of recrystallized grains increased. The average sizes of precipitated MgZn2 phases increased with the increase in either the initial forging temperature or MDF passes, and the volume fractions gradually decreased with increasing the initial forging temperature or decreasing the MDF passes. With decreasing the initial MDF temperature, thermal expansion mismatch strengthening slightly decreased while fine-grain strengthening and Orowan strengthening gradually increased, resulting in a gradual increased yield strength. The elongation of the present nanocomposite gradually increased from 8.2% after 1 MDF pass to 22.7% after 6 MDF passes, while both yield strength and ultimate tensile strength did not change significantly. This could be ascribed to that although the fine-grain strengthening gradually reduced, there was no significant change in the Orowan strengthening caused by MgZn2 phases with increasing the number of MDF passes. [ABSTRACT FROM AUTHOR]

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