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Stable VN micro-alloying for WH630E steel plate can be achieved by utilization of blowing nitrogen at the bottom of BOF and refining process. Steel plate WH630E with thickness of 8-25 mm was rolled by TMCP process and was treated by normalizing. By comparing mechanical properties and microstructure changes in as-rolled plate and normalized plates, it was found out that ferrite grain size can be refined by normalizing process and the low temperature impact energy can be improved by normalizing. The main Strengthening mechanism for normalized WH630E steel plate was ferrite grain refining, grain refining plays a more stronger role than V(CN) precipitation strengthening. Cold crack and reheated crack can be avoided by preheating treatment with no more than 170 ̊C before welding WH630E plate, strength and toughness for welded joint can have good match with the base metal by the process of 15∼35 kJ/cm welding heat input energy and 500∼580 ̊C SR(stress relief)heat treatment. Yield strength of normalized high strength pressure vessel steel plate can be improved by VN micro-alloying, and then the wall thickness of pressure vessel can be thinned or operating pressure can be increased, therefore overall weight of transportable pressure vessel can be reduced, and there will be significant economic and social benefits for the application of this kind pressure vessel steel plate. [ABSTRACT FROM AUTHOR]

SiC particles reinforced AZ91D Mg matrix composites with different particle contents fabricated by a ultrasonic method were extruded at 350 °C. Hot extrusion eliminated the “island” particle distribution, and evidently improved SiC particles distribution of the composites. However, hot extrusion induced particle cracking besides the improvement of SiC particles distribution. There existed more cracked particles in the particle-rich zones. During extrusion, SiC particles stimulated the nucleation of dynamic recrystallization in the matrix. Dynamic recrystallization is also sensitive to the particle content on a local scale in the composites. As SiC contents increased, the yield strength of the composites increased. However, the ultimate tensile strength increases of the composites were small as the SiC contents increased from 10% to 20%, because the improvement of ultimate tensile strength caused by the strengthen effects of SiC particles was offset by extrusion-induced particle cracking. [ABSTRACT FROM AUTHOR]

The present study dealt with the AZ91 alloy subjected to multidirectional forging (MDF) under decreasing temperature conditions with emphasizing on relationship between microstructures and mechanical properties generated by MDF. The obtained results showed that grains of the alloy were gradually refined while the amount of the second phase precipitated along the grain boundaries was increased with increasing the MDF passes and decreasing the MDF temperature. Compared with the as-cast alloy, yield strength, ultimate tensile strength and elongation of the AZ91 alloy after MDF under decreasing temperature conditions were simultaneously increased. As the numbers of MDF passes were gradually increased and the MDF temperature was gradually decreased, the yield strength was gradually decreased, suggesting that texture softening may overwhelm the strengthening due to the grain refinement as well as the homogeneous distribution of precipitates. [ABSTRACT FROM AUTHOR]

Highlights: [•] The solidification rates significantly affect the CNTs distribution. [•] Uniform CNTs distribution was achieved in the composites. [•] The tensile properties of the composites follow the Kelly–Tyson formula well. [Copyright &y& Elsevier]

Highlights: [•] Bimodal size SiCp/AZ31B composites were fabricated. [•] The influence of bimodal size SiCp for matrix alloy was determined. [•] Mechanical properties of bimodal size SiCp/AZ31B composite were enhanced significantly. [ABSTRACT FROM AUTHOR]

Abstract: A ceramic coating was formed on the surface of AZ31 magnesium alloy by plasma electrolytic oxidation (PEO) in the silicate solution with and without borax doped. The composition, morphology, elements and roughness as well as mechanical property of the coating were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and reciprocal-sliding tribometer. The results show that the PEO coating is mainly composed of magnesia. When using borax dope, boron element is permeating into the coating and the boron containing phase exist in the form of amorphous. In addition, the microhardness and compactness of the PEO coating are improved significantly due to doped borax. [Copyright &y& Elsevier]

Abstract: SiCp/Mgph name="sbnd" />Ca composites with three volume fractions (5%, 10% and 15%) were successfully fabricated by stir casting. The particle distributions were fairly uniform in all composites, although most particles were segregated along grain boundaries in the micro-scale level. Interfacial reaction products were not observed at the interface between SiCp and matrix. SiCp affected the size and shape of the second phases as well as their distribution in the matrix. In the 5% composite, many large second phases were observed at the particle surfaces. As the particle content was increased up to 10%, large second phases were hardly observed at the SiCp surfaces. Moreover, the second phases mainly existed in the form of fine flake in the 10% and 15% composite, unlike the alloy and 5% composite in which the second phases were large. The effect of SiCp on the second phases significantly influenced the mechanical properties of the composites. Compared with the matrix alloy, 15% composites had good room temperature and high temperature mechanical properties. [Copyright &y& Elsevier]

Abstract: Particulate reinforced magnesium matrix nanocomposites were fabricated by semisolid stirring assisted ultrasonic vibration. Compared with the as-cast AZ91 alloy, the grain size of matrix alloy in the SiCp/AZ91 nanocomposite stirring for 5min was significantly decreased due to the addition of SiC nanoparticles. SiC nanoparticles within the grains exhibited homogeneous distribution although some SiC clusters still existed along the grain boundaries in the SiCp/AZ91 nanocomposite stirring for 5min. With increasing the stirring time, agglomerates of SiC nanoparticles located along the grain boundaries increased. The ultimate tensile strength, yield strength and elongation to fracture of the SiCp/AZ91 nanocomposite stirring for 5min were simultaneously improved compared with the as-cast AZ91 alloy. However, the ultimate tensile strength and elongation to fracture of the SiCp/AZ91 nanocomposite decreased with increasing the stirring time. [Copyright &y& Elsevier]

In this study, both AZ91 alloy and nano-SiCp/AZ91 composite were subjected to multi-pass forging under varying passes and temperatures. The microstructure and mechanical properties of the alloy were compared with its composite. After six passes of multi-pass forging at a constant temperature of 400 ℃, complete recrystallization occurred in both the AZ91 alloy and composite. The decrease of temperature and the increase of passes for the multi-pass forging led to further refinement of dynamic recrystallized grains and dynamic precipitation of second phases. The grain size of the nano-SiCp/AZ91 composite was smaller than that of the AZ91 alloy under the same multi-pass forging condition, which indicated that the addition of SiC nanoparticles were beneficial to grain refinement by pinning the grain boundaries. The texture intensity for the 12 passes of multi-pass forging with varying temperatures was increased compared with that after nine passes. The ultimate tensile strength is slightly decreased while the yield strength was increased unobviously for the AZ91 alloy with the decrease of temperature and the increase of the passes for the multi-pass forging. Under the same condition of multi-pass forging, the yield strength of the composite was higher than that of the AZ91 alloy due to the Orowan strengthening effect and grain refinement strengthening resulting from externally applied SiC nanoparticles and internally precipitated second phases. By comparing the microstructure and mechanical properties between the AZ91 alloy and nano-SiCp/AZ91 composite, the strength-toughness properties of the composites at room temperature were affected by the matrix grain size, texture evolution, SiC nanoparticles distribution and the precipitated second phases. [ABSTRACT FROM AUTHOR]

In this study, low volume fraction SiCp/AZ91 magnesium matrix nanocomposites billets intended for structural applications were synthesized using semisolid stirring assisted ultrasonic vibration, leading to the dispersion of SiC nanoparticles. Both the AZ91 alloy and nanocomposite billets were then subjected to isothermal multidirectional forging (IMDF). Micrographic observations illustrated that the mean grain size of the developed nanocomposite showed an initial increase after 3 IMDF passes, followed by a decrease after 6 IMDF passes compared to the AZ91 alloy. This indicated that the effect of dispersed SiC nanoparticles on the inhibition of the dynamic recrystallization grains growth was impaired due to the present high IMDF temperature. The improved yield strength of the nanocomposite could be attributed to Orowan strengthening effect related to the dispersed SiC nanoparticles as well as the second phases precipitated far from the dynamic recrystallization grains. [ABSTRACT FROM AUTHOR]

AZ91 alloy was subjected to multidirectional forging (MDF) and the relationship between microstructures and mechanical properties generated by MDF were investigated. The results showed that after 1 MDF pass grain size of the alloy decreased compared with as-cast alloy, and the amount of recrystallization grains increased when the MDF temperature increased from 250 °C to 400 °C. With increasing the MDF passes at 350 °C, grains of the alloy were gradually refined. A typical basal texture was obtained after 1 MDF pass, and then the basal pole scattered with the increase of MDF passes. Mg 17 Al 12 phases were precipitated along grain boundaries during MDF, which could hinder the growth of recrystallization grains. Both tensile strength and elongation to failure of the alloy were significantly enhanced till 3 MDF passes with increasing the MDF passes. [ABSTRACT FROM AUTHOR]

Magnesium-based composites with high specific properties have been found to be promising candidate for automotive and aerospace applications where materials are subjected to impact and elevated temperature conditions. AZ31B Mg alloy reinforced by 1.0 vol% silicon carbide nanoparticles was investigated under quasi-static and impact conditions. The impact tests were carried out on the split Hopkinson pressure bar in the temperature range from 243 K to 473 K. The temperature and strain rate effect on the compressive mechanical response of the material are discussed. The strain rate sensitivity, strain hardening behavior and temperature sensitivity of the material have been quantified. Comparative results of AZ31B and AZ31B reinforced with 0.5 vol% silicon carbide nanoparticles at room temperature (298 K) are also presented in terms of nanoparticle and its volume fraction effects. Quantitative conclusions are obtained of the strain rate effect on the mechanical behavior of these materials. All materials investigated have strong strain-rate dependence. The strength increases as the strain rate increases. The addition of nanoparticles was found to increase the material strength and energy absorption capability though an increase in ductility can be hardly observed. [ABSTRACT FROM AUTHOR]

Abstract: SiCp/AZ91 magnesium matrix composite was fabricated by stir casting. The as-cast ingots were cut into cylindrical billets, and then forged at different temperatures (320, 370, 420, 470 and 520°C) at a constant RAM speed of 15mm/s with 50% reduction. The microstructure evolution of the composites during forging was investigated by optical microscope, scanning electron microscope, and transmission electron microscope. The texture of the forged composites was measured by neutron diffraction. Mechanical properties of the composite at different forging temperatures were tested by tensile tests at room temperature. It was found that a strong basal plane texture formed during forging, and the intensity of basal plane texture weakened as forging temperatures increased. The particle distribution in the composite was significantly improved by hot forging. Typical microstructures were obtained after forging at different temperatures and the composite with different microstructures offered different mechanical properties during tensile test. [Copyright &y& Elsevier]

Abstract: Magnesium matrix composites reinforced by graphite particles were fabricated using stir casting with graphite particle size of 50μm and graphite particle volume fractions of 5, 10, 15 and 20%, respectively. The as-cast composites were extruded at 300°C with an extrusion ratio of 12:1. The experimental results reveal that the graphite particles play an important role on the tensile properties and damping capacities of the composites. The strength increases with the addition of 5% graphite particles, but decreases with further addition of graphite particles. The strain amplitude independent damping increases significantly as the graphite particle volume fraction increases from 0 to 10%, but almost keeps constant when the volume fraction exceeds 10%. Two damping peaks are found at 150 and 350°C, respectively. The damping peak around 150°C is considered to be caused by movable boundary slip, and the damping peak around 350°C is inferred to be recrystallization peak. [Copyright &y& Elsevier]

Abstract: Equal channel angular pressing (ECAP) of the in situ Mg2Si reinforced Mg composite was performed with route Bc up to 8 passes using a 90° die. Refinement and re-distribution of the reinforced phase Mg2Si was investigated. Bulk texture development during ECAP was characterized by neutron radiation. Results showed that only the eutectic Mg2Si (Type-II) was proposed to be effective for preparing the in situ Mg2Si/Mg composite. Neutrons texture analysis briefly illustrated that a 〈00.2〉 basal fiber with the obtainment of less shear effect was formed. But the asymmetry of basal fiber around the ECAP direction was also observed. Both uniform texture and homogeneity distribution of Mg2Si particles played an important role in the tensile behavior of ECAPed composite. [Copyright &y& Elsevier]

Abstract: Microstructure and texture development of the equal channel angular pressed (ECAP) pure Mg with different rotation routes of A, Bc and C were investigated and related to the tensile mechanical property. Results showed that grain size was greatly decreased after 1 pass but varied with processing routes after the following ECAP. Due to a relatively high processing temperature, the refinement degree was limited via these three routes processing. Different preferred orientations of the basal plane were formed with three routes processing and there existed a rotation angle in (0002) pole figure from normal direction to transverse direction. Negative slope of the yield stress versus d−1/2 was obtained with routes Bc processing, which was attributed to the texture modification. Texture strengthening greatly increased the 0.2% yield strength, but decreased the ductility. [Copyright &y& Elsevier]

Abstract: Carbon/phenolic (C/PH) composites have been widely used for impact protection and energy-absorption, the proper design of which require appropriate material characterization data and stress–strain relations suitable for wide range of strain-rate conditions. Firstly, sophisticated quasi-static and medium–high strain-rate compression tests are conducted to study the mechanical behaviors of C/PH composites, and one nonlinear viscoelastic constitutive model is proposed based on the experimental results. Light gas gun tests are subsequently conducted to derive the impact Hugoniot curve and high-pressure equation of state (EOS). Finally, the proposed material model and EOS are built into a cross-format centered difference scheme to preliminarily investigate the wave effects of C/PH composites. It is established that the viscoelastic model, the equation of state along with the 1-D difference code are very effective in capturing the mechanical properties of C/PH composites over a wide range strain-rates. [Copyright &y& Elsevier]