金属纤维多孔材料力学性能研究现状

详细论述了金属纤维多孔材料的拉伸性能、剪切性能、压缩性能和冲击性能等力学性能的研究进展,并简要叙述了应力波在多孔材料内部传播的研究现状,最后指出未来应加强金属纤维多孔材料的动态冲击性能及应力波在多孔材料内部的传播、衰减机制研究,从而进一步扩大金属纤维多孔材料的应用领域。     

金属纤维多孔材料吸声性能研究现状

简要描述了金属纤维多孔材料的吸声原理及其应用领域,重点阐述了材料厚度、材料结构、金属纤维直径、孔隙度等因素对其吸声性能的影响规律。指出要深入系统研究各因素对吸声性能影响程度的优先次序,为制备具有良好吸声性能的金属纤维多孔材料提供理论支持和技术指导。     

金属纤维多孔材料力学性能的研究进展

金属纤维多孔材料既有金属的性质,又因内部存在着大量的孔隙而具有一系列的功能特性,是一类优良的结构功能一体化材料.本文主要分析了金属纤维多孔材料的制备方法,讨论了该材料的力学性能,并着重介绍了近几年该领域的最新研究进展.     

生物医用多孔钛的力学性能及孔结构变形行为（英文）

多孔钛材料因其优良的综合性能被视为最有潜力的生物医用材料之一。考虑到生物材料在使用过程中必然受到力的作用,重点研究了多孔钛的力学性能及其孔结构变形行为。采用添加造孔剂的粉末烧结方法制备孔隙率为36%~66%、平均孔径为230μm的多孔钛。采用扫描电镜观察孔结构形貌,通过室温压缩测试检测力学性能。多孔钛的弹性模量和抗压强度分别为1.86~14.7 GPa和85.16~461.94 MPa,具力学性能与人骨的力学性能相近。建立了多孔钛的相对屈服强度和相对密度间关系,结果表明相对密度是影响多孔钛力学性能和变形的主要因素。对于低相对密度的多孔钛而言,其变形方式为孔壁的屈服、弯曲和屈曲;而对于高相对密度的多孔钛,其变形方式主要为孔壁的屈服和弯曲。     

HD+SPS多孔镁的制备及其组织性能研究

利用氢化脱氢(HD)+放电等离子烧结(SPS)工艺制备了多孔镁块体材料,研究了不同MgH_2含量下多孔镁孔隙率、孔结构及压缩和吸能性能。结果表明,HD+SPS法制备的总孔隙率分别为7.5%和17.8%的多孔镁,且其孔径尺寸细小,内部组织均匀;孔隙率为17.8%的多孔镁具有相对较低的压缩屈服强度43 MPa,单位体积吸能较高,为34.04 MJ/m~3,最大能量吸收效率为1.42。17.8%孔隙率的多孔镁压缩应力-应变曲线较7.5%孔隙率的多孔镁有相对较低的屈服强度及较长的应力平台阶段,在能量吸收材料应用上更具优势。     

纤维烧结多孔钛及其表面生长仿生Ca-P涂层

采用钛纤维烧结法制备了多孔钛，并应用混合碱-热处理对其表面进行活化处理，然后在过饱和钙磷溶液中进行表面钙磷涂覆。测试了多孔钛的压缩性能，分析了涂层的形貌、元素含量和相组成。结果表明，制备的多孔钛为三维贯通结构，孔隙度在29％～84％，孔隙尺寸为100～800gm。当孔隙度为55％～60％时，压缩屈服强度为150～230MPa，弹性模量为4．0～4．2GPa，与骨组织相近。经表面钙磷涂覆处理的多孔钛在模拟体液中浸泡3天后，内外孔壁均被类骨磷灰石覆盖，表现出良好的诱导骨生长特性。     

FeAl金属间化合物多孔材料压缩力学性能

针对本课题组采用元素混合粉偏扩散-反应合成-粉末烧结方法制备的Fe-40at%Al金属间化合物多孔材料,采用单轴压缩实验研究其压缩应力-应变曲线特征以及孔隙率对其力学性能的影响规律,并通过扫描电镜实验揭示其微观断裂机理。结果表明:FeAl多孔材料的压缩应力-应变曲线可分为弹性、屈服、强化和破坏4个阶段,其中较大孔隙率的FeAl多孔材料表现出明显的非线性弹性特征;随着孔隙率的增大,其压缩屈服极限变化不大,而弹性模量和抗压强度显著降低;其断口特征宏观上表现为脆性断裂,微观上为微观沿晶断裂。比较FeAl多孔材料的理论值E*和实测值E可知,非均匀Plateau多孔结构细观力学模型不适合高密度多孔材料,但可以较好地预测中密度多孔材料的弹性模量。     

FeAl金属间化合物多孔材料压缩力学性能研究

针对本课题组采用元素混合粉偏扩散-反应合成-粉末烧结方法制备的Fe-40at%Al金属间化合物多孔材料,采用单轴压缩实验研究其压缩应力-应变曲线特征以及孔隙率对其力学性能的影响规律,并通过扫描电镜实验揭示其微观断裂机理。结果表明：FeA1多孔材料的压缩应力-应变曲线可分为弹性、屈服、强化和破坏四个阶段,其中较大孔隙率的FeAl多孔材料表现出明显的非线性弹性特征;随着孔隙率的增大,其压缩屈服极限变化不大,而弹性模量和抗压强度显著降低;其断口特征宏观上表现为脆性断裂,微观上为微观沿晶断裂。比较FeAl多孔材料的理论值E_*和实测值E可知,非均匀Plateau多孔结构细观力学模型不适合高密度多孔材料,但可以较好地预测中密度多孔材料的弹性模量。     

通孔多孔铝的压缩性能研究

在采用复模铸造工艺制备孔径d=2.5~3.50 mm,孔隙率P=56.8%~86.1%通孔多孔铝的基础上,通过单轴压缩试验,研究了通孔多孔铝的压缩性能和吸能能力。通孔多孔铝单轴压缩应力-应变曲线,呈现线弹性变形、平缓塑性变形和压缩紧实3个阶段。通孔泡沫铝的压缩屈服强度、吸能能力随孔隙率增大而减小,采用Gibson-Ashby的模型拟合通孔多孔铝的压缩屈服强度。     

蜂窝铝压缩变形机制及性能的有限元模拟

蜂窝材料是一种结构比较简单的多孔材料，是研究多孔材料的基础。采用有限元法，对7种不同相对密度的蜂窝铝的压缩过程进行了模拟研究，分析蜂窝铝的变形机制、屈服强度、平台应变和能量吸收特性，结果表明，随着相对密度的增加，蜂窝铝的屈服强度和能量吸收能力增大，而平台应变减小，变形带也越难产生。通过压缩过程的应力分布情况图分析蜂窝铝的压缩变形机制；比较了模拟结果和经验结果，验证了经验公式的适用条件。     

RHEOLOGY FEATURE OF SIMPLE METAL MELT

The rheology feature of Sb, Bi melt and alloys was studied using coaxial cylinder high-temperature viscometer. The results showed that the curve of torsion-rotational speed for Sb melt presents a linear relation in all measured temperature ranges, whereas for the Bi melt, the curve presents obvious non-Newtonian feature within the low temperature range and at relative high shear stress. The rheology feature of Sb80Bi20 and Sb20Bi80 alloy melts was well correlated with that of Sb and Bi, respectively. It is considered that the rheology behavior of Sb melt plays a crucial role in Sb80Bi20 alloy and that of Bi melt plays a crucial role in Sb20Bi80 alloy.     

Microstructures and Mechanical Properties of a Newly Developed Austenitic Heat Resistant Steel

The effect of heat treatment on the microstructures and mechanical properties of a newly developed austenitic heat resistant steel(named as T8 alloy) for ultra-supercritical applications have been studied. Results show that the main phases in the alloy after solution treatment are γ and primary MX. Subsequent aging treatment causes the precipitation of M_(23)C_6 carbides along the grain boundaries and a small number of nanoscale MX inside the grains. In addition, with increasing the aging temperature and time, the morphology of M_(23)C_6 carbides changes from semi-continuous chain to continuous network.Compared with a commercial HR3C alloy, T8 alloy has comparable tensile strength, but higher stress rupture strength. The dominant cracking mechanism of the alloy during tensile test at room temperature is transgranular, while at high temperature, intergranular cracking becomes the main cracking mode, which may be caused by the precipitation of continuous M_(23)C_6 carbides along the grain boundaries. Typical intergranular cracking is the dominant cracking mode of the alloy at all stress rupture tests.     

The 15th Global Foundry Sourcing Conference 2014held in Qingdao China

Organized by Suppliers China Co., Ltd and co-organized by the National Technical Committee 54 on Foundry of Standardization Administration of China, the 15th Global Foundry Sourcing Conference 2014 （hereinafter referred to as FSC 2014） was successfully held on Sep. 23rd in Grand Regency Hotel, Qingdao. More than 500 delegates from home and abroad attended this conference, including over 130 purchasers from 20 countries and 380 domestic and foreign suppliers.     

Secondary Recrystallization Behaviors of Grain-Oriented 6.5 wt% Silicon Steel Sheets Produced by Rolling and Nitriding Processes

By rolling and nitriding processes, 0.23- to 0.3-mm-thick grain-oriented 6.5 wt% silicon steel sheets were produced. The core losses of grain-oriented 6.5 wt% silicon steel at frequencies ranging from 400 Hz to 20 k Hz were lower than that of the grain-oriented 3 wt% silicon steel with the same thickness by 16.6–35.8%. The secondary recrystallization behavior was investigated by scanning electron microscopy, energy-dispersive spectroscopy, and electron backscattered diffraction. The results show that the secondary recrystallization in high-silicon steel sheets develops more completely as the nitrogen content increases after nitriding, secondary recrystallized grain sizes become larger, and the sharpness of Goss texture increases. Because more {110}116 grains in the subsurface and the central layer of the sheets have a lot of 20°–45° high-energy boundaries in addition to Goss grains, {110}116 can be the main component through selective growth during secondary recrystallization when the inhibitor quantity is not enough and inhibitor intensity is weaker. The increases in nitrogen content can increase the inhibitor intensity and hinder abnormal growth of a mount of {110}116 grains and therefore enhance the sharpness of Goss texture.     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

LASER CLADDED TiCN COATINGS ON THE SURFACE OF TITANIUM

Laser cladded coatings of TiCN were produced on the surface of titanium. To obtain the optimal techniques, several conditions were tested by varying the laser scanning rate. The choice of shielding gas was also studied. The cladded coatings were then evaluated from the surface mechanics point of view based on their microhardness. The microstructure of some interesting samples was investigated by optical micrographs (OM). The results showed that under the condition of fixed pulse frequency and pulse width, the laser scanning rate and the shielding gas are the main factors influencing the components of coatings. TiCN coatings were decompounded and oxidized during the cladding process in the condition of no shielding gas of N2. X-ray diffraction results indicated that the composite coatings composed of TiCN, TiC, Ti2N, and TiO2 were produced using appropriate techniques. The results indicated that the best condition in terms of the surface microhardness is obtained when the scanning rate is 1.5mm / s, the pulse frequency is 15Hz, the pulse width is 3.0ms, and N2 is chosen as the shielding gas. The microhardness of the composite coatings is about 1331kg · mm - 2, which is about 4 times that of the substrate. The optical micrographs indicated that the cladding zone is made up of TiCN, TiO2, and some interdendritic Ti, but the diffusion zone mainly consists of the dendrites phase, and the cladded depth is about 80m, which is more than 2 times that of the laser nitrided sample. There were no microcracks or air bubbles in the cladded sample, which was cladded using the above optimal techniques.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Microstructure and Mechanical Properties of X80 Pipeline Steel Joints by Friction Stir Welding Under Various Cooling Conditions

X80 pipeline steel plates were friction stir welded(FSW) under air, water, liquid CO_2 + water, and liquid CO_2 cooling conditions, producing defect-free welds. The microstructural evolution and mechanical properties of these FSW joints were studied. Coarse granular bainite was observed in the nugget zone(NZ) under air cooling, and lath bainite and lath martensite increased signifi cantly as the cooling medium temperature reduced. In particular, under the liquid CO_2 cooling condition, a dual phase structure of lath martensite and fi ne ferrite appeared in the NZ. Compared to the case under air cooling, a strong shear texture was identifi ed in the NZs under other rapid cooling conditions, because the partial deformation at elevated temperature was retained through higher cooling rates. Under liquid CO_2 cooling, the highest transverse tensile strength and elongation of the joint reached 92% and 82% of those of the basal metal(BM), respectively, due to the weak tempering softening. A maximum impact energy of up to 93% of that of the BM was obtained in the NZ under liquid CO_2 cooling, which was attributed to the operation of the dual phase of lath martensite and fi ne ferrite.     

INDUSTRY NEWS

China Securities News reported on March 21, 2014： Guangdong Hongtu Wuhan Die Casting Co., Ltd. （Wuhan Hongtu）, a wholly owned subsidiary of Guangdong Hongtu Technology （Holdings） Co., Ltd., held a groundbreaking ceremony recently. With the registered capital of 50 million Yuan, Wuhan Hongtu has a total land area of 100,000 square meters and a plant construction area of 72,000 square meters. It is expected to have a production capacity of about 30,000 tonnes of aluminum castings annually after it is put into production.