Xueshan Xiao

Intense milling nanocrystalline Fe73.5Cu1Nb3Si13.5B9: a soft magnetic material in powdered form

Abstract The change of structure by intense milling on the nanocrystalline Fe 73.5 Cu 1 Nb 3 Si 13.5 B 9 alloy was investigated. The magnetic properties of nanocrystalline Fe 73.5 Cu 1 Nb 3 Si 13.5 B 9 dust cores (core of compacted powder) were studied. It was found that the nanostructured ribbons obtained from the crystallization of amorphous state by a proper annealing treatment could be changed into amorphous powder via short time milling. By increasing the milling time, the milled powder return to crystallization. It was also found that the permeability of the nanocrystalline dust cores had nearly not any changes in the frequency range from 1 to 100 kHz. The quality factor Q of the nanocrystalline dust cores increased gradually with increasing frequency. The quality factor Q of nanocrystalline dust cores became higher at the frequency over 50∼70 kHz in comparison with that of the permalloy dust core.

22Cr High-Mn-N Low-Ni Economical Duplex Stainless Steels

A new family of economical duplex stainless steels in which N or Mn was substituted for Ni with composition of 22Cr-8. OMn-xNi-1. OMo-0. 7Cu-0. 7W-0. 3N (x = 0. 5–2. 0) have been developed by examining the micro-structure, mechanical and corrosion properties of these alloys. The results show that these alloys have a balanced ferrite-austenite relation. In addition, the alloys are free of precipitation of sigma phase and Cr-nitride when solution-treated at 750 to 1300 °C for 30 min. The yield strength, tensile strength and fracture elongation values of experimental alloys solution-treated at 1 050 °C for 30 min are about 500, 750 MPa and 40. 0%, respectively. Low-temperature impact properties can be improved distinctly with the increase of nickel content. Among the designed DSS alloys, the alloy with Ni of 2. 0% is found to be an optimum alloy with proper phase proportion, better low-temperature impact properties and higher pitting corrosion resistance compared with those of other alloys. The mechanical and corrosion properties and lower production cost of the designed DSSs are better than those of AISI 304.

New Economical 19Cr Duplex Stainless Steels

New economical duplex stainless steels (DSSs) containing 19Cr-6Mn-xNi-1.0Mo-0.5W-0.5Cu-0.2N (xxa0=xa00.5 to 2.0) were developed, and the microstructure, impact property, and corrosion resistance of the alloys were studied. The ferrite content increases with the solution treatment temperature, but decreases with an increase in nickel. The sigma phase is not found precipitating in the alloys treated with solution from 1023xa0K to 1523xa0K (750xa0°C to 1250xa0°C). The low-temperature impact energy of the experimental alloys increases first and then decreases rapidly with an increase in nickel, which is mainly due to the martensite transformation with an increase in austenite. The alloys have a better mechanical property and pitting corrosion resistance than AISI 304. Among the designed DSS alloys, 19Cr-6Mn-1.3Ni-1.0Mo-0.5W-0.5Cu-0.2N is found to be an optimum alloy with proper phase proportion, a better combination of mechanical strength and elongation, and higher pitting corrosion resistance compared with those of the other alloys.

A New Resource-Saving, High Chromium and Manganese Super Duplex Stainless Steels 29Cr-12Mn-2Ni-1Mo-xN

A new family of resource-saving, high chromium and manganese super duplex stainless steels (DSSs), with a composition in mass percent, % of Cr 0. 29, Mn 0. 12, Ni 2. 0, Mo 1. 0, and N 0. 51–0. 68, has been developed by examining the effect of N on the microstructure, mechanical properties and corrosion properties. The results show that these alloys have a balanced ferrite-austenite relation. The austenite volume fraction decreases with the solution treatment temperature, but it increases with an increase in N content. The increases in nitrogen enhance the ultimate tensile strength (UTS) and reduce the ductility of the material slightly. The pitting corrosion potential increases first and then decreases with an increase in nitrogen content when the amount of N arrives to 0. 68%. The yield stress and ultimate tensile strength of solution-treated samples were more than 680 and 900 MPa, the elongation of experimental alloys are higher than 30%, respectively, what is more, the pitting potentials were beyond 1100 mV.

A New Series of Mo-free 21. 5Cr-3. 5Ni-x W-0. 2N Economical Duplex Stainless Steels

A new series of economical Mo-free duplex stainless steels 21.5Cr-3.5Ni-x W-0. 2N (x = 1. 8 – 3. 0, mass%) have been developed. The effects of W on mechanical properties and corrosion resistance were investigated, and the microstructures were analyzed by optical microscopy, X-ray diffraction, transmission electron microscopy and electron backscatter diffraction. The designed steels have a balanced ferrite-austenite relation and are free of sigma phase after solution treatment at 750 – 1300 °C for 30 min followed by water-quenching, whereas a small number of Cr23C6 precipitates were found after solution treatment at 750 °C. After solution treatment at 1050 °C, the steel with 1. 8% (mass percent) W exhibits the highest room temperature tensile strength due to the strongest work hardening effect, while the steel with 3. 0% (mass percent) W exhibits the highest fracture elongation owing to the transformation-induced plasticity (TRIP) effect. The ductile-brittle transition (DBT) and martensite transformation are respectively found in the ferrite and austenite, which deteriorates the impact properties of the steels with the increase of W content. The corrosion resistance of the designed steels is improved with the increase of W content. The pitting resistance of austenite is obviously better than that of ferrite for the designed alloys. Among the designed steels, the steel with 1. 8% (mass percent) W is found to be an optimum steel with excellent comprehensive properties and lowest production cost.

A New Economical Sigma-Free Duplex Stainless Steel 19Cr-6Mn-1. 0Mo-0. 5Ni-0. 5W-0. 5Cu-0. 2N

A new resource-saving duplex stainless steel with composition of 19Cr−6Mn−1. 0Mo−0. 5Ni−0. 5W−0. 5Cu−0. 2N has been developed, and the microstructure, mechanical properties and corrosion properties have been investigated. The results show that the alloy has a balanced ferrite-austenite relation, and the ferrite content rises with the solution treatment temperature. The designed alloy is free of precipitation of sigma phase when aged at 650, 750 and 850 °C for 3 h, respectively, whereas a few Cr23C6 precipitates are found after being aged at 750 °C for 8 h. Charpy impact tests indicate that the impact energy of the alloy is 68, 200 and 220 J at —40, 0 and 25 °C, respectively. The designed alloy solution treated at 1 050 °C for 30 min has a much higher yield strength and similar corrosion resistance compared with those of AISI 304 austenitic stainless steel. Moreover, the production cost of the alloy is about

Evolutions of Microstructure and Properties During Cold Rolling of 19Cr Duplex Stainless Steel

1 000 per ton which is lower than that of AISI 304.

Effects of Alloy Elements on Oxidation Resistance and Stress-Rupture Property of P92 Steel

AbstractEvolutions of microstructure, mechanical, and corrosion propertiesn of 19Cr (Fe-18.9Cr-10.1Mn-0.3Ni-0.261N-0.030C-0.5Si) duplex stainless steel have been investigated during cold rolling at room temperature. Dislocation slip dominated deformation mode of ferrite phase. However, deformation mechanism of austenite phase was different with the increasing cold-rolling reductions. Dislocation slip and strengthening effect of twin boundaries caused pile-up phenomenon at the initial deformation stage. When the amount of cold-rolling reduction attained greater than 50xa0pct, induced α′-martensite appeared in deformed austenite phase. Hardness of austenite phase was higher than that of the deformed ferrite because of its higher strengthening effect during cold-rolling process. Cold-rolling deformation caused deterioration of the pitting corrosion resistance in 3.5xa0wtxa0pct NaCl aqueous solution. Pitting corrosion always initiated in the ferrite phase and the phase boundary in the solution-treated alloy. Additional pitting holes appeared in deformed austenite phase because of the decrease in corrosion resistance caused by dislocation accumulation and induced α′-martensite.

Improvement of Stress-rupture Life for Modified-HR6W Austenitic Stainless Steel

Effects of alloy elements Cr, W, Ce, and Si on oxidation behavior at 750xa0°C in air and stress-rupture properties of P92 steel have been investigated. The proper increase in elements Cr, W, and Ce improved to varying degrees both oxidation resistance by either facilitating more protective Cr2O3 or modifying surface morphologies and stress-rupture life largely attributed to the formation of fine Laves phase. The excessive addition of Si significantly improved oxidation resistance of P92 steel, but dramatically impaired the stress-rupture life due to the formation and coarsening of Laves phase. The results indicate that proper additions of Cr, W, and Ce are beneficial for the comprehensive property of P92 steel.

Thermal stability and glass-forming ability of Y-Ce-Co-Al bulk metallic glasses

Stress-rupture life of HR6W austenitic stainless steel modified with B and Mg additions was measured, and the microstructures were analyzed by optical microscopy, X-ray diffraction, scanning electron microscopy and transmission electron microscopy equipped with energy dispersive spectroscopy The results indicated that the enhancement of the stress-rupture life was mainly due to the precipitation with B in the elemental form at the grain boundaries, and the improvement of the form of carbides at grain boundaries and the removal of O and S elements by addition of Mg. The micro-alloying elements have a beneficial effect on stress-rupture life of the modified-HR6W austenitic stainless steel at high temperature.