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Sun S.-Q.,Hebei University of Science and Technology | Sun S.-Q.,Hebei Key Laboratory of Material Near net Forming Technology
Fenmo Yejin Cailiao Kexue yu Gongcheng/Materials Science and Engineering of Powder Metallurgy | Year: 2015

Magnetization measuring in synchronism with cryogenic treatment and tempering of AHP T15M powder metallurgy high speed steel (PM HSS) at different states was carried out by vibration sample magnetometer (VSM). Effect of cryogenic treatment on tempering transformation of AHP T15M PM HSS was studied. The results show that ferrite content in annealed PM HSS is 71.5% (volume fraction); Martensitic volume fraction value in quenched steel is approximately 45.2%. Martensitic volume fraction values in the first, second and third time tempered steel are approximately 68.5%, 71.0% and 71.3%, respectively. With addition of cryogenic treatment, martensitic volume fraction values in cryogenic treated and the first, second and third time tempered steel are approximately 59.8%, 69.9%, 70.9% and 71.3%, respectively. Cryogenic treatment moves up martensite transformation from retained austenite, suppresses carbide precipitation in retained austenite, and especially promotes a larger number (about 2.3%) of fine carbides precipitation in martensite. With cryogenic treatment, the hardness of steel increases by 52 HV0.1. © 2015, Central South University. All right reserved.


Li J.H.,Yanshan University | Li J.H.,Hebei University of Science and Technology | Li J.H.,Hebei Key Laboratory of Material Near net Forming Technology | Li Q.,Yanshan University | And 5 more authors.
Materials Letters | Year: 2015

The effects of boron(B) on the microstructure and mechanical properties of Zr3Al-based alloys were investigated. Zr-6Al-XB alloys (X=0, 0.02, 0.05, 0.1, 0.15 wt%) were first smelted in a non-consumable electric arc furnace. The ingots were then hot rolled four passes at 950 °C and annealed at 800 °C for 4 h to obtain Zr3Al-based alloys. Analysis results showed that B can dramatically refine the grains of Zr3Al-based alloys: doping 0.1 wt% B could reduce the grain size of Zr3Al-based alloy from 500 μm to 30 μm; grain size decreases with the amount of B doped in the alloy until a certain threshold amount is reached, and then excessive amount of B (0.15 wt% B doped Zr3Al-based alloy) leads to larger grain size. Tensile strength and elongation of B doped Zr3Al-based alloys were also improved with higher level of grain refinement. Annealing changed the fracture mode of all samples from brittle to ductile and B doped can further enhance ductility. © 2015 Elsevier B.V. All rights reserved.


Gao Y.,Hebei University of Science and Technology | Gao Y.,Hebei Key Laboratory of Material Near net Forming Technology | Wei J.,Xingtai Technician College | Yang X.C.,Hebei University of Science and Technology | And 2 more authors.
Applied Mechanics and Materials | Year: 2013

Based on the theory of two-phase flow, the flow field of dust particles inside the wet electrostatic precipitator with SIMPLE algorithm was modeled used a k -ε standard turbulence model and simulated numerically. Establishment of finite element model for the entity porous plate was done with grid refined locally. The number and installation position of porous plates, the diverging angle of the horn inlet and the opening rate of air distribution plates were changed in this simulation. And the studies on the airflow distribution of the inlet section were performed, in which the flow of key parameters for air flow uniform distribution are given. The experimental verification of optimal results of simulation model suggested that the simulation results and the experimental results were coincident. © (2013) Trans Tech Publications, Switzerland.


Hu J.-W.,Hebei Key Laboratory of Material Near net Forming Technology | Hu J.-W.,Hebei University of Science and Technology | Ma J.,Hebei Key Laboratory of Material Near net Forming Technology | Ma J.,Hebei University of Science and Technology | Zhang X.,Hebei University of Science and Technology
Cailiao Rechuli Xuebao/Transactions of Materials and Heat Treatment | Year: 2015

Three relatively environmental-friendly pickling and activation process were chosen as the pretreatment for electroless Ni-P plating on AZ91HP magnesium alloy. The pickling solutions were H3PO4+Na2MoO4, Na3PO4·12H2O+H3PO4+KMnO4 and H3PO4+Na3PO4·12H2O, respectively. NH4HF2 was used as activation solution. The metallography morphology and polarization experimental results in 3.5%NaCl solution show that the Ni-P coating pretreated with H3PO4+Na3PO4·12H2O pickling and NH4HF2 activating is bright and has a strong adhesion with the substrate. Furthermore its corrosion resistance is superior. The surface roughness after the pickling pretreatment has an effect on the smoothness and brightness of electroless Ni-P plating on magnesium alloys while that after the activating pretreatment has an effect on the adhesion between the coating and the substrate. ©, 2015, Editorial Office of Transactions of Materials and Heat Treatment. All right reserved.


Li J.H.,Yanshan University | Li J.H.,Hebei University of Science and Technology | Li J.H.,Hebei Key Laboratory of Material Near net Forming Technology | Gao Y.,Hebei University of Science and Technology | And 6 more authors.
Materials Research Innovations | Year: 2015

ZrAl alloys with three different Al contents (6.0, 7.0, 8.0 wt-%) were melted by non-consumable electric-arc furnace. X-ray diffraction and metallographic analysis were used to study the microstructure and phase composition of ZrAl alloys, then rockwell hardness and tensile properties were tested. The results showed that Al significantly enhanced the hardness of pure Zr, and hardness of as-cast ZrAl alloys increased with the increase of Al content. Homogeneous microstructure of Zr3Al-based alloys could be obtained by annealing, and the annealing time must increase with the increase of Al content. With the increase of annealing time, grain size of Zr3Al-based alloys increased, tensile strength and elongation decreased. This implied that when ensuring complete peritectoid reaction conditions, we should minimise annealing time to avoid coarse grain for the purpose of obtaining Zr3Al-based alloys with excellent mechanical properties. In addition, annealing changed the fracture mode of ZrAl alloys from brittle to ductile. © W. S. Maney & Son Ltd 2015.

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