Run Wu

Microstructure and mechanical properties of Mo2FeB2 ceramic-steels with Nb/V addition

ABSTRACT Seven series of Mo2FeB2 ceramic-steels with Nb/V content between 0 and 6 wt-% had been successfully fabricated by liquid phase reaction sintering. The microstructure was studied by means of field emission scanning electron microscope, energy dispersive spectroscopy and X-ray diffractometry. The hardness (HRA), transverse rupture strength (TRS) and wear resistance were also measured. The results reveal that the grain size decreased with the increase of Nb content, but had little change with the increase of V content. With the increase of Nb/V content, the hardness and TRS both enhance first and then descends. Mo2FeB2 ceramic-steels with 4 wt-% Nb content show the highest hardness and TRS of HRA 90.6 and 1970 MPa and the best dry sliding wear resistance.

Correlation of morphological anisotropy and Lankford value of deep drawing sheets hot-rolled by compact strip production

Cold-rolled steel sheets in automotive applications require an excellent deep draw ability, which is characterized by the Lankford value (r-value). In this study, a correlation was identified between r-value and pancake-shaped grain flatness which is indicated as the ratio of grain diameter in the rolling direction (RD) and normal direction (ND) of sheets (dr/dn). A mathematical model

Microstructure and Mechanical Properties of Mo 2 FeB 2 Based Cermets with/without Nb Addition

\left( {r = e^{0.345\left( {d_n^{ - 1/2} - d_r^{ - 1/2} } \right)} } \right)

Effect of nano-sized precipitates on the crystallography of ferrite in high-strength strip steel

was developed to calculate r-value by the microstructure of steel sheets hot-rolled by compact strip production (CSP). It is shown that the r-value is higher, if the microstructure of steel sheet is of pancake-shaped grains elongated in the rolling direction. The calculated r-value is confirmed to fit exactly to the measured one from the large-scale production.

The Properties of Low Yield Ratio and High Heat Input Welding Construction Steel and the Microstructure of HAZ

The grain refining of C-Mn steel on CSP line was investigated in this paper. The grain size was about 100μm after rolling by stand F1 and then decreased all the way of the rolling process(stands F2-F6) to 15μm. The strengthening mechanisms, grain refinement strengthening, solution strengthening, precipitation strengthening and dislocation strengthening, were figured out to develop a physical metallurgy model for prediction of the properties. It was noted that there is an agreement between the predicted properties and the measured ones of the steel.

Nucleation Mechanism of IGF in the HAZs of Ti-Killed HSLA Steel

Four series of Mo2FeB2 based cermets with different Nb content between 0 and 6 wt.% had been successfully fabricated by liquid phase reaction sintering (LPRS). The densification behavior, microstructural characteristics and mechanical properties of Mo2FeB2 based cermets were investigated. The result shows that with the increase of Nb content, the grain size decreased, but more pores formed. Meanwhile, the hardness and transverse rupture strength both be increased first and then decreased. Mo2FeB2 based cermets doped with 4 wt.% Nb content have the highest hardness and TRS of HRA 90.6 and 1970 MPa.

Effects of Alloying Elements on Structure of Plasma Electrolytic Oxidation Ceramic Coatings on Aluminum Alloys

The microstructures and impact absorbed energies at various temperatures were investigated for steel strips hot rolled to thickness reductions of 95.5%, 96.0%, 96.5%, 97.0%, and 97.5%. Results indicate that grain refinement can be realized with an increase in hot rolling reduction. Besides, finer precipitates can be achieved with an increase in hot rolling reduction from 95.5% to 97.0%. The impact absorbed energy decreases with a decrease in testing temperature for steel strips hot rolled to 95.5%, 96.0%, and 96.5% reductions in thickness. However, in the case of steel strips hot rolled to 97.0% and 97.5% reductions in thickness, the impact absorbed energy remained almost constant with a decrease in testing temperature.

Sulfides Precipitation during Transformation of a High Sulfur Alloy Steel

For strip steel with the thickness of 1.6 mm, the yield and tensile strengths as high as 760 and 850 MPa, respectively, were achieved using the compact strip production technology. Precipitates in the steel were characterized by scanning and transmission electron microscopy to elucidate the strengthening mechanism. In addition, intragranular misorientation, Kernel average misorientation, and stored energy were measured using electron backscatter diffraction for crystallographic analysis of ferrite grains containing precipitates and their neighbors without precipitates. It is found that precipitates in specimens primarily consist of TiC and Ti4C2S2. Ferrite grains containing precipitates exhibit the high Taylor factor as well as the crystallographic orientations with {012}, {011}, {112}, or {221} plane parallel to the rolling plane. Compared with the intragranular orientation of adjoining grains, the intragranular misorientation of grains containing precipitates fluctuates more frequently and more mildly as a function of distance. Moreover, the precipitates can induce ferrite grains to store a relatively large amount of energy. These results suggest that a correlation exists between precipitation in ferrite grains and grain crystallographic properties.