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1143 results about "Grain growth" patented technology

In materials science, grain growth is the increase in size of grains (crystallites) in a material at high temperature. This occurs when recovery and recrystallisation are complete and further reduction in the internal energy can only be achieved by reducing the total area of grain boundary. The term is commonly used in metallurgy but is also used in reference to ceramics and minerals.

Method for removing cracks of Rene104 nickel-based superalloy during laser additive manufacturing

The invention provides a method for removing cracks of Rene104 nickel-based superalloy during laser additive manufacturing, and belongs to the fields of additive manufacturing and superalloy. Aiming at solving the problem that cracks are liable to occur to Rene104 nickel-based superalloy with a high Al content and a high Ti content (Al+Ti>5%) during laser additive manufacturing, by designing laserforming parameters and sub-regional scanning strategies, generation of large-size cracks in a formed part is suppressed; then stress relief annealing is used for completely removing residual stress in the formed part; and discharge plasma sintering treatment is adopted for removing the cracks in the formed part, and grain growth during the sintering process is suppressed. The scheme that after the formed part is obtained through laser additive manufacturing, in combination with stress relief annealing and discharge plasma sintering treatment, the cracks in the formed part are removed is proposed for the first time. By using the method for preparing the Rene104 nickel-based superalloy with the high Al content and high Ti content, no cracks are found in the formed part, and the tensile strength of the formed part at the room temperature can reach 1300 MPa or higher.
Owner:CENT SOUTH UNIV

High-coercivity and high-stability neodymium iron boron magnet and preparation method based on crystal boundary reconstruction

The invention discloses a high-coercivity and high-stability neodymium iron boron magnet and a preparation method based on crystal boundary reconstruction. The preparation method comprises the steps of separating design and preparation of main alloy and crystal boundary phase alloy powder, nano-modification of crystal boundary phase, powder mixing, magnetic field profiling, isostatic pressing, sintering and thermal treatment. According to the high-coercivity and high-stability neodymium iron boron magnet and the preparation method is based on crystal boundary reconstruction and combines with a rich heavy rear earth novel crystal boundary phase and nano-modification technology, namely the rich heavy rare earth novel crystal boundary phase is redesigned and synthesized, in the process of magnetic sintering and tempering, magnetic hardening is achieved through spread of the heavy rare earth element to the boundary layers of the principle phase crystal grain, and thus a high-coercivity magnetic is prepared under the condition that no or less heavy rear earth is added in the principle phase. Meanwhile the distribution of the crystal boundary and the form of the crystal grain boundary are optimized through a nano-modification method, a pinning domain wall restrains counter magnetic field nucleation and crystal grain growth, and thus high coercivity and high stability of the neodymium iron boron is achieved. The high-coercivity and high-stability neodymium iron boron magnet and preparation method based on crystal boundary reconstruction is simple in process, low in cost and suitable for large-scale volume production.
Owner:ZHEJIANG UNIV

Industrialized preparation method of WC-Co hard alloy with low cost and high performance

ActiveCN101624673ASolve the problem that it is difficult to mix evenlyReduce energy consumptionPolyethylene glycolPrice ratio
The invention relates to an industrialized preparation method of a WC-Co hard alloy with low cost and high performance, which belongs to the technical field of hard alloys and powder metallurgy. The method comprises the following steps: taking WO2.9, Co3O4 and carbon soot as raw materials, and computing the usage ratio of the three materials according to the requirement of the Co content in a final hard alloy block material; adding 0-1.0 percent by weight of grain growth inhibitor into the prepared WC-Co composite powder, and adding polyethylene glycol as a forming agent into a ball milling tank 4-8 hours before ball milling is finished, wherein 30-80ml of polyethylene glycol is added into the powder material per kilogram; acquiring WC-Co mixed powder with a nanocrystal structure after ball milling, and putting the mixed powder into a mould for press forming after vacuum drying; and sintering the mixed powder stock after press forming in a mode of vacuum sintering or low-pressure sintering. The industrialized preparation method markedly shortens a production period, the provided integrated preparation course markedly reduces the production cost while ensuring the high performance of the hard alloy and has a high performance-price ratio, and the preparation method is suitable for industrialized scale production.
Owner:北硬科技香河有限公司

Tungsten-doped boride-coated lithium battery anode material and preparation method thereof

The invention is applicable to the technical field of lithium batteries and provides a tungsten-doped boride-coated lithium battery anode material and a preparation method thereof. Firstly, tungsten source is dissolved in water, sprayed onto a mixed material of a ternary precursor and lithium source and then stirred to obtain a dried material; the dried material is placed and baked in a saggar toobtain a tungsten-doped ternary anode material; finally, metal boride is added to the tungsten-doped ternary anode material, stirred uniformly and sintered at a certain temperature to obtain the tungsten-doped boride-coated lithium battery anode material. According to the tungsten-doped boride-coated lithium battery anode material, the synergistic effect between tungsten doping and the metal boride takes full advantage of the tungsten doping and the metal boride, the tungsten doping can significantly inhibit grain growth and shorten the transmission distance of Li+, MgB2 as a superconductor has fast ion transmission properties, and the tungsten doping and the metal boride improve rate capability of the tungsten-doped boride-coated lithium battery anode material. Meanwhile, the boride coating can inhibit the reaction between the surface of an electrode material and electrolyte, thereby improving the safety performance and cycle stability of the tungsten-doped boride-coated lithium battery anode material.
Owner:GEM (HUBEI) NEW ENERGY MATERIALS CO LTD

Method for preparing nano oxide dispersion reinforced superfine crystal tungsten-based composite material

The invention provides a method for preparing a nano oxide dispersion reinforced superfine crystal tungsten-based composite material. The method comprises the following steps of: taking 0.1 to 1 weight percent of micro tungsten powder, nano yttrium oxide powder or yttrium metal powder and 0 to 2 weight percent of titanium metal powder or molybdenum powder or tantalum powder, blending the materials, mechanically alloying the materials, sintering discharge plasma and the like to prepare the superfine crystal tungsten composite material. The method has the following advantage that: the nearly full-densification superfine crystal tungsten-based composite material can be obtained by the method for preparing the nano oxide dispersion reinforced superfine crystal tungsten-based composite material. Complex phase doping of yttrium oxide or yttrium metal and titanium metal, molybdenum or tantalum powder not only realizes sintering densification of tungsten at a lower temperature, but also inhibits grain growth of tungsten crystals during sintering. The tungsten crystal grain size of the yttrium oxide reinforced superfine crystal tungsten-based composite material prepared by adopting the method is less than or equal to 3 microns, and the composite material has good mechanical property and thermal shock resistance.
Owner:UNIV OF SCI & TECH BEIJING

Preparation method of complex phase ceramic material containing zirconium boride

InactiveCN102173813AControlling chemical reaction driving forcesControl the severity of the reactionBorideMaterial defect
The invention relates to a preparation method of a complex phase ceramic material containing zirconium boride, relating to a preparation method of ceramic materials and aiming to overcome the material defects of abnormal crystal grain growth, phase clustering, and the like which are caused by difficult control and overhigh partial temperature in the traditional reaction sintering preparation method and solve the problems of tissue uniformity and comprehensive mechanical property of the complex phase ceramic material. The preparation method comprises the following steps of: 1, placing zirconium oxide and a boron-containing compound or a boron-containing composite into a ball mill to form composite powder; 2, drying the composite powder, then crushing, and screening through a sieve of 200 meshes to obtain uniform mixed powder; 3, carrying out mould pressing or cold isostatic pressing on the mixed powder, and then carrying out pressureless sintering, hot pressing sintering or hot isostatic pressing sintering to obtain the complex phase ceramic material containing the zirconium boride. The complex phase ceramic material containing the zirconium boride has uniform crystal grain size and distribution, the fracture toughness of 3.5-7.5 MPa.m<-1 / 2> and the bending strength of 250-700 MPa and can be used in the field of high-temperature resistant structural members and the like.
Owner:HARBIN INST OF TECH
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