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Zhang W.,Institute of Materials Engineering | Zhang W.,Zhejiang University of Technology | Zhang W.,Canny Elevator Co.
Jinshu Rechuli/Heat Treatment of Metals | Year: 2016

Molybdenum (Mo) and high-Cr cast iron mixed powder was laser cladded on the surface of 20 steel substrate under two different scanning speed (100 mm/min and 300 mm/min), and microstructure and hardness of the laser cladding layer with different Mo contents (0.5%, 3%, 5%, 7.5% and 10%) were tested by scanning electron microscope and hardness tester, respectively. The results show that the Mo and high-Cr cast iron laser cladding layer has better properties such as finer grains, higher density without crack and gas hole. When the scanning speed is slower (100 mm/min), the adding of Mo make the crystal grain smaller, the long striped pearlite changed into cellular dendritic austenite. Under different Mo contents, the average hardness of cladding layer is 160, 172, 193, 212 and 226 HV0.2, respectively. When the scanning speed is faster (300 mm/min), the adding of Mo can restrain the growth of carbides and promote long striped original alloy carbides change into square block carbides and lamellar carbides, which is conductive to restrain cracking. Under different Mo contents, the average hardness of cladding layer is 586, 612, 637, 682 and 712 HV0.2, respectively. © 2016, Chinese Mechanical Engineering Society of Heat Treatment. All right reserved. Source

Zhou Q.,University of Sydney | Blanchard P.,University of Sydney | Kennedy B.J.,University of Sydney | Reynolds E.,University of Sydney | And 9 more authors.
Chemistry of Materials | Year: 2012

Two Ce 3+ containing double perovskites Ba 2CeMO 6 (M = Nb and Ta) have been prepared through the use of mildly reducing conditions, and the Ce valence state has been shown to be +3 through Ce L-edge X-ray absorption measurements. Both oxides adopt a monoclinic structure in I2/m at room temperature and undergo two phase transitions upon heating, a discontinuous I2/m → R3̄ and a continuous R3̄ → Fm3̄m transition. Analysis of the first order I2/m → R3̄ transitions is impeded by the complex peak shapes and diffuse scattering evident in the synchrotron powder diffraction data because of domain wall effects. © 2012 American Chemical Society. Source

Zenker R.,Institute of Materials Engineering
65th ABM International Congress, 18th IFHTSE Congress and 1st TMS/ABM International Materials Congress 2010 | Year: 2010

The paper describes specific requirements to be met by the beam guiding systems for geometry and material related surface treatment of Al and Mg alloys. For different EB technologies (remelting, densifying, alloying, dispersing) the influence of beam parameters and energy transfer conditions (single- and multi-process technologies) on microstructure of the materials and its properties will be discussed. Under optimum conditions fine grained and homogenous layers with a thickness up to 1.5...5 mm without pores or cracks and with a very good metallurgical contact to the basic material without gaps can be produced. Using multi-process technology in case of EB alloying the maximum hardness of layers on Al alloys AlZnMgCu1.5, AlSi10Mg, as well as AlSi21Ni7Cu3 and AlSi30 achieved values up to 500HV0.1 and wear rate decreases by a factor of 10. The scratch energy density by EB alloying achieves a maximum improvement of factor 10...25. The EB alloying of Mg alloys MgAl9Zn1 and MgAl3Zn1, performed by single- and double-staged processes results in layers thickness up to 3 mm and noteworthy changes of mechanical properties (hardness by factor 4 up to 300HV0.3). In this case corrosion resistance is nearly comparable to those of a rapid solidified Al alloy. Copyright © (2010) by Associação Brasileira de Metalurgia Materiais e Mineração (ABM). Source

Wolf S.,Institute of Materials Engineering | Martin S.,Institute of Materials Science | Kruger L.,Institute of Materials Engineering | Martin U.,Institute of Materials Science
Materials Science and Engineering A | Year: 2014

The influence of strain rate and temperature on the resulting mechanical behaviour of a cast metastable austenitic CrMnNi-TRIP/TWIP steel was investigated. At ambient temperature and below, the formation of α'-martensite dominates causing a pronounced strain hardening. Various analytical models are available in literature and are mostly based on rule of mixture concepts (e.g. Ludwigson and Berger [22] and Narutani et al. [25]). These models were developed for commercial metastable alloys with medium stacking fault energy (SFE). However, for the herein-investigated alloy with very low SFE these models were found to be limited in describing the strain rate dependent material behaviour. A new model is presented predicting the flow stress of metastable alloys incorporating strain rate sensitivity, transformation strain, martensite kinetics and adiabatic heating. © 2013 Elsevier B.V. Source

Martin S.,Institute of Materials Science | Richter S.,Institute of Materials Science | Decker S.,Institute of Materials Engineering | Martin U.,Institute of Materials Science | And 2 more authors.
Steel Research International | Year: 2011

Dense TRIP-matrix composites containing 5 vol.% Mg-PSZ as reinforcing phase were produced by employing the spark plasma sintering technique. A continuous and seamless interface between the ceramic particles and the steel matrix was achieved. Compression tests revealed better mechanical properties of the 5 vol.% Mg-PSZ-TRIP steel composites in comparison with both, pure and Al 2O 3 reinforced TRIP steel. The underlying deformation mechanism within the austenitic matrix entailed a pronounced martensite formation. An additional phase transformation was observed within the ZrO 2 particles. The enhanced mechanical properties of the 5 vol.% Mg-PSZ composite are dedicated to the transformation strengthening of the ceramic particles. Finally a model of the reinforcing mechanism is proposed. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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