Explore the vast range of titles available.

The x wt%graphene-Ti composites（x = 0,0.2,0.3 and 0.4） were obtained using the powder metallurgy method.The X-ray diffraction results demonstrated that the peak intensity of graphene increased monotonically with increasing graphene content.Furthermore,the number of grain boundary and interface between graphene and matrix increased as graphene increased,which led to a sharp rise of thermal resistances.The thermal conductivity and specific heat capacity of composites initially decreased drastically with addition of graphene,but then increased with increasing graphene content from 0.2 to 0.4 wt%.This phenomenon was connected with the graphene content and the characteristics of Ti matrix（pores,grain boundary and interface between graphene and matrix）.The variation of the compressive strength of composites was attributed to the interaction effects of the average grain size of the Ti matrix（d_m） and the volume fraction（V_f） and aspect ratio（A） of graphene.

Tungsten inert gas（TIG） welding was performed on 2.7 mm thick commercial extruded AZ31 B magnesium alloy plates. We investigated the effect of post-weld heat treatment（PWHT） on the microstructure, mechanical properties and precipitated phase of the weld joints. The results showed that during the annealing treatment（200 ℃-1 h, 250 ℃-1 h, 300 ℃-1 h, 350 ℃-1 h, 400 ℃-1 h, and 450 ℃-1 h）, the average grain size in the weld seam was the minimum after annealing at 400 ℃ for 1 hour, and then abnormally grew up after annealing at 450 ℃ for 1 hour. The mechanical properties enhanced when the joints were processed from 200 ℃-1 h to 400 ℃-1 h but sharply decreased with increasing annealing temperature. In contrast to the annealing treatment, solution treatment（250 ℃-10 h, 300 ℃-10 h, 350 ℃-10 h, 400 ℃-10 h, and 450 ℃-10 h） exhibited a better ductility but a slight deterioration in tensile strength. Especially speaking, no eutectic compounds（such as Mg17 Al12） were observed in the weld seam. The supersaturated Al atoms were precipitated in a coarse spherical shape dispersed in the weld seam. The precipitated Al atoms dissolved in the matrix substances at the condition（400 ℃-1 h） or（250 ℃-10 h）. The solution treatment caused grain coarsening and precipitated Al atoms dissolved in the weld seam substantially, which resulted in a drop in micro-hardness at the weld seam compared to the area of the annealed joints.

The nanocrystalline microstructure of the surface of 316 stainless steel (316SS) induced by surface mechanical attrition treatment (SMAT) was determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The technique of hydrogen embrittlement was first used to obtain the information of the brittleness cleavage plane. The effects of SMAT and the following annealing process on the corrosion behavior of 316SS were investigated by potentiodynamic polarization curves and potentiostatic critical pitting temperature measurements. The results demonstrated that the nanocrystalline layer with an average grain size of 19 nm was produced. However, there were lots of cracks on the surface, which led to the degradation in the corrosion resistance of 316SS after SMAT. Nevertheless, after annealing treatment, the corrosion resistance of the nanocrystalline surface had been improved greatly. The higher the annealing temperature, the better was the corrosion resistance.

Mg–9Li–3Al–1.6Y alloys were prepared through mixture method. The microstructure, mechanical properties, and corrosion resistance of the as-cast and asextruded alloys were studied by optical microscopy（OM）,scanning electronic microscopy（SEM）, X-ray diffraction（XRD）, mechanical properties testing, and electrochemical measurement. The as-cast Mg–9Li–3Al–1.6Y alloy with the average grain size of 325 lm is composed of b-Li matrix, block a-Mg, and granule Al2Y phases. After extrusion, the grain size of the as-cast alloy is obviously refined and reaches to 75 lm; the strength and elongation of the extruded alloy are enhanced by 17.20 % and49.45 %, respectively, owing to their fine microstructure and reduction of casting defects. The as-extruded alloy shows better corrosion resistance compared to the as-cast one, which may be related to the low stored energy and dislocation density in the extruded alloy, also the homogenization treatment before extrusion.

It is shown that an adapted powder sintering process can successfully prepare a 24.0%-35.5% porous titanium composite using 20μm Ti powder and rice husk particles ranging in size between 250μm and600μm.The phase constituents of the porous Ti composite samples were determined by X-ray diffraction（XRD）pattern sintered at 1250℃.The generation of silicon in the form of a TiSi2 solid solution,injected into the substrate,illustrates the solid solution strengthening effect.The average grain size of the tested sample and the grain boundary area increase along with the silicon content.This indicates that silicon is dispersed within the green compact of Ti.As the distance from a hole becomes greater,the nanohardness increases until it reaches a maximum hardness of 3.5GPa at approximately 1.5mm.This may be due to the solid solution strengthening of SiO2.However,nanohardness is 3.3GPa at a distance of approximately 0.5mm from a hole′s edge.The compressive strength is measured to be in the range of 440-938 MPa.The strain reaches 14.8%-16.6% under compression testing.A large number of cleavage steps appear following a fracture.The observed fracture is a brittle fracture.Porous Ti composites with about 36% porosity have promising potential biomaterial applications,specifically related to bone implants and biological bearings.

The transformation behavior, microstructural evolution and mechanical properties were compared in a coldrolled Nb–Mo microalloyed 6.5Mn alloy after intercritical annealing（IA） and quenching and partitioning（Q ＆ P）,respectively. The thermodynamic calculation and theoretical analysis were used to determine the optimal heat treatment parameters. The Q ＆ P samples exhibited relatively higher strength with relatively low ductility, mainly due to the hard martensite matrix, which resulted in continuous yielding behavior upon loading, whereas the IA samples showed the significantly improved ductility, which benefited from the more sufficient transformation-induced plasticity（TRIP） effects and the softer ultrafine ferrite matrix. The dependence of yield point elongation（YPE） of IA samples on grain size demonstrated that the YPE value was in the reverse proportional relationship to the average grain size, which agreed well with theoretical analysis.

Hot compression deformation behaviors of medium carbon Cr-Ni-Mo Nb steel were investigated at deformation temperatures ranging from 1223 to 1423 K and strain rates of 0.1, 1 and 5 s^-1. Dynamic recovery （DRV） and dynamic recrystallization （DRX） were observed during the hot compression deformation. For all of the samples, DRX occurred at deformation temperatures above 1323 K at different strain rates, while below 1223 K, no DRX was observed. The activation energy of the tested steel was determined as 386.06 kJ/mol. The ratio of critical stress to peak stress and the ratio of critical strain to peak strain were 0. 835 and 0.37, respectively. Kinetic equations interpreting the DRX behavior of the tested steel were proposed, and the corresponding parameters including the volume fraction and the average grain size were determined. Moreover, the microstructures induced under different deformation conditions were analyzed.

In this work, the Mg–5Al–2Ca alloy was extruded at 573, 623 and 673 K, with a ratio of 16：1 and a constant speed of 3 mm/s. Results demonstrate that the Al2Ca particle is formed in Mg–5Al–2Ca alloy. The size, amount and distribution of Al2Ca particles are influenced evidently by extrusion temperature. Unlike previous reports, the intensity of basal texture increases with increasing extrusion temperature, and the reasons are analyzed and given. Even though the average grain size increases as the extrusion temperature increased from 573 to 623 K, the YS, UTS and elongation of asextruded Mg–5Al–2Ca alloy are almost kept the same at 573 and 623 K. The reason is speculated as the balance of grain size, Al2Ca phase and texture at the two temperatures. The work hardening rate depends on extrusion temperature, and the largest θ value of Mg–5Al–2Ca alloy is obtained when the extrusion was performed at 623 K.

The metal microstructure during the hot forming process has a significant effect on the mechanical properties of final products. To study the microstructural evolution of the cross wedge rolling （CWR） process, the microstructural model of GH4169 alloy was programmed into the user subroutine of DEFORM-3D by FORTRAN. Then, a coupled thermo-mechanical and microstructural simulation was performed under different conditions of CWR, such as area reduction, rolling temperature, and roll speed. Comparing experimental data with simulation results, the difference in average grain size is from 11.2% to 33.4% so it is verified that the mierostructural model of GH4169 alloy is reliable and accurate. The fine grain of about 12-15 p.m could be obtained by the CWR process, and the grain distribution is very homogeneous. For the symmetry plane, increasing the area reduction is helpful to refine the grain and the value should be around 61%. Moreover, when the roiling temperature changes from 1000 to 1100℃ and the roll speed from 6 to 10 r.min-1, the grain size of the rolled piece decreases first and then increases. The temperature may be better to choose the value around 1050℃ and the speed less than 10 r-min-1.

Polyaniline nanotubes and PANI-ZnO nanocomposites were prepared by the simplified Template-Free method. The experimental results indicated that the average diameter of Polyaniline nanotubes was approximately 150-200 nm. The average crystallite size of ZnO in PANI-ZnO composites was 27 nm. Moreover, the as-prepared samples were characterized by scanning electron microscopy（SEM）, FT-IR spectroscopy（FTIR） and X-ray diffraction（XRD）. Photocatalytic properties of the obtained samples were investigated by the photodegradation analysis of orange II and methylene orange dye. The as-prepared PANIZnO nanocomposites exhibited much higher photocatalytic activity than pure PANI nanotubes. During 2 h photocatalytic courses under UV irradiation, the degradation ratios of Orange II and methyl orange using PANIZnO nanocomposites were 90.3% and 84.5%, respectively. Furthermore, this method can be extended to prepare other organic-inorganic semiconductor composites based composite catalysts.