Cu基块状非晶晶化过程的微区变形及力学性能

在玻璃转变温度以下选择350、400、475及600 K进行1 h的等温退火,用纳米压痕仪、扫描电镜等研究Cu基块状非晶晶化过程的力学性能及变形。Cu基块状非晶在纳米压头作用下体现弹-塑性变形方式,载荷—位移曲线和压痕周边多重剪切带的特征证明了塑性变形的存在。350 K退火试样具有较大的压痕硬度HV和弹性模量E值及较小的塑性变形量dn值;400 K退火后,HV和E值显著减小,dn值明显增大;475 K退火后,有少量晶体相析出,但合金以非晶的特性为主,HV和E值继续减小,dn值继续增大;600 K退火后,晶体相进一步长大和析出,其固溶强化和弥散强化使合金的HV和E值有所增加,dn值略有减小。对塑性变形机理进行了初步分析。     

块体非晶合金剪切带的原子力纳米压痕行为

通过原子力显微镜(AFM)纳米压痕实验研究传统纳米压痕实验形成的Fe基非晶合金剪切带区域及未变形区域的变形;结合压痕形貌实时原位观测,探讨块体非晶合金塑性变形局域化的原因.结果表明最大载荷44.6μN下,材料的剪切带、剪切带间和未变形区域的AFM纳米压痕残余面积分别为3274.7、2976.5和2879.2nm2,对应的硬度分别为13.62、14.98和15.49GPa,剪切带区域的硬度值比未变形区域的硬度值降低了约10%,说明塑性变形过程中,过剩自由体积的产生使剪切带结构发生软化.     

热处理工艺对Fe-Co-Zr-Mo-W-B大块非晶合金断裂韧度的影响

采用电弧熔炼母合金、感应加热熔化、铜模吸铸工艺，制备了厚度为1mm的板状Fe-Co-Zr-Mo-W-B系Fe基大块非晶合金，铸态试样表面及断口光亮，具有典型的金属光泽，但脆性严重。本文采用压痕试验法研究了热处理工艺对铸态Fe基大块非晶合金脆性的影响。结果表明，合适的退火工艺可使Fe基大块非晶合金的断裂韧度提高到铸态的260％。     

Fe-Co-B-Si-Nb-Cr块体非晶合金在纳米压痕过程中的变形行为

利用纳米压痕技术研究直径为3 mm的{[(Fe0.6Co0.4)0.75B0.2Si0.05]0.96Nb0.04}96Cr4块体非晶合金的变形行为以及加载速率对其塑性变形行为的影响规律.结果表明:该块体非晶合金在低加载速率下表现出显著的锯齿流变,而在高的加载速率下表现为连续的塑性变形;在纳米压痕过程中,该块体非晶合金出现室温蠕变现象,且其硬度值随着加载速率的增大而减小.     

退火温度对Mg61Cu28Gd11块体非晶结构与性能的影响

对Mg61Cu28Gd11块体非晶在其玻璃转变温度以下温度(325、350、375和400 K)等温退火1 h,用X射线衍射仪(XRD)、差热扫描量热仪(DSC)、纳米压痕仪、扫描电子显微镜(SEM)、显微维氏硬度计等分析研究了低温退火对其热稳定性、微区力学性能及变形的影响,并分析了塑性变形机理.结果表明,低温退火后非晶原子的短程有序性增加,非晶结构的稳定性变差,并在400K发生部分晶化.同时,在325～375 K范围内,显微硬度和弹性模量E随退火温度的升高而增大,塑性变形量Dn和最大压入深度Dmax减小;400 K退火后,由于少量析出的晶体相与压头下新产生的自由体积相互作用,合金抵抗变形能力减弱,显微硬度和弹性模量E降低,Dn和Dmax提高.     

Cu基块体非晶合金的力学行为

铜基大块非晶合金Cu52.5Ti30Zr11.5Ni6与Cu50.5Ti30Zr11.5Ni6Al2具有高的压缩断裂强度,分别为2212MPa与2286MPa;伸长率均达到2.1%。断口微观形貌分析表明,Cu基大块非晶合金具有3种不同类型的微观形貌,分别与断口的3个断裂扩展区域相对应,并且观察到绝热升温导致的断面局部熔化现象。显微硬度与纳米压痕测试证实了非晶合金的弹塑性变形机制。     

非晶态Zr47Ni30Ti23合金中纳米晶的发展

非晶材料的纳米晶化可在非晶基体中弥散分布纳米晶粒制成纳米晶/非晶复合材料，从而提高力学/物理性能。为此韩国人介绍了非晶Zr47Ni30Ti23合金的纳米晶形成过程。 首先用高纯Ti，Zr，Ni原料用氩弧熔炼成合金锭。用熔融旋转法以30m/s的筒表面速度摔成非晶带，用差式扫描量热计(DSC)以 20℃/min~40℃/min的加热/冷却速度，在氩气下研究非晶带的晶化行为，用X射线衍射(XRD)和透射电镜(TEM)分析和标定结晶相 的结构和形态。由Zr-Ni-Ti三元相图可知，Zr47Ni30Ti23合金中的平衡相包含大量的Laves相和Zr2Ni相及少量α-Zr(Ti)固溶体。…     

Fe含量对Zr60Cu40-xFex相分离非晶合金组织结构、电阻性能和纳米压痕行为的影响

在Zr60Cu40单相非晶合金中引入与合金次要组元Cu具有正混合焓的Fe元素,设计了Zr60Cu40-xFex相分离非晶合金,研究了 Zr60Cu40-xFex三元合金的液-液相分离行为.结果表明,二元Cu-Fe合金的液态组元不混溶区域可以延伸至三元Zr60Cu40-xFex合金中;在快速凝固条件下,该合金在冷却过程中会发生液-液相分离,形成富Cu和富Fe两液相;基于Zr60Cu40-xFex合金液-液相分离凝固特征,考察了 Fe含量对Zr60Cu40-xFex合金组织及相结构的影响,讨论了Zr60Cu40-xFex体系组织演变及相形成机制.Zr60Cu20Fe20合金在冷却过程中液-液相分离形成的富Zr-Cu和富Zr-Fe两液相分别发生玻璃转变,最终形成了高数量密度(1024/m3数量级)的纳米富Cu非晶粒子(尺寸为2～10nm)分布在富Fe非晶基体上的相分离非晶合金组织.研究了该合金样品的电阻性能和纳米压痕行为,讨论了 Zr60Cu20Fe20合金晶化过程的电阻反常变化行为,并分析了 Zr60Cu20Fe20合金的纳米尺度相分离组织结构对剪切转变区的影响.     

Ce基非晶合金制备及室温变形行为的研究

采用铜模吸铸法制备φ2 mm的Ce70Al10Cu20、Ce69Al10Cu20Co1和Ce69Al10Cu20Ag1合金棒材.利用X射线衍射(XRD)、示差扫描量热法(DSC)和纳米压痕法(Nanoindentation)研究添加元素Ag、Co对Ce基非晶合金形成能力、热稳定性及室温变形行为的影响.结果表明,添加Ag、Co能显著提高Ce基非晶合金的玻璃形成能力和热稳定性能.Ce70Al10Cu20和Ce69Al10Cu20Ag1合金在高加载速率下出现锯齿流变;而Ce69Al10Cu20Co1合金在实验加载速率下表现为连续塑性变形.此外,三种Ce基非晶合金在压痕保载段均出现明显的蠕变现象且蠕变量随加载速率增加而增大.     

Zr基块体金属玻璃蠕变行为的纳米压痕研究

在本工作中，通过纳米压痕实验研究了加载速率和保载时间对(Zr0.6336Cu0.1452Ni0.1012Al0.12)97.4Er2.6块体金属玻璃（BMG）的蠕变变形行为的影响。实验结果表明，合金试样的蠕变位移随着加载速率或保载时间的增加而增大。另一方面，合金样品的硬度（H）也随着加载速率或保载时间的增加而降低。合金试样在纳米压痕过程中具有尺寸效应，合金试样的硬度随着压痕深度的增加而降低。合金试样在纳米压痕过程中具有锯齿流动现象，并且该现象具有速率依赖性。具体而言，随着加载速率的减小，锯齿流动现象更加明显。合金试样的蠕变应力指数随着加载速率或保载时间的增加而减小。     

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.     

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 80?滋m, 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.     

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.     

Microstructure,Mechanical Properties and Corrosion Behavior of Extruded Mg–Zn–Ag Alloys with Single-Phase Structure

Mg–Zn–Ag alloys have been extensively studied in recent years for potential biodegradable implants due to their unique mechanical properties,biodegradability and biocompatibility.In the present study,Mg–3Zn-x Ag(wt%,x=0.2,0.5 and0.8)alloys with single-phase crystal structure were prepared by backward extrusion at 340°C.The addition of Ag element into Mg–3Zn slightly influences the ultimate tensile strength and microstructure,but the elongation firstly increases from12%to 19.8%and then decreases from 19.8%to 9.9%with the increment of Ag concentration.The tensile yield strength,ultimate tensile strength and elongation of Mg–3Zn–0.2Ag alloy reach up to 142,234 MPa and 19.8%,respectively,which are the best mechanical performance of Mg–Zn–Ag alloys in the present work.The extruded Mg–3Zn–0.2Ag alloy also possesses the best corrosion behavior with the corresponding corrosion rate of 3.2 mm/year in immersion test,which could be explained by the single-phase and uniformly distributed grain structure,and the fewer twinning.     

Growth Morphologies of a Binary Alloy with Low Anisotropy in Directional Solidification

Two new classes of growth morphologies, called doublons and seaweed, were simulated using a phase-field method. The evolution of doublon and seaweed morphologies was obtained in directional solidification. The influence of orientation and velocity on the growth morphology was investigated. It was indicated that doublons preferred growing with its crystallographic axis aligned with the heat flow direction. Seaweed, on the other hand, could be obtained by tilting the crystalline axis to 45°. Stable doublons could only exist in a range of velocity regime. Beyond this regime the patterns formed would be unstable. The simulation results agreed with the reported experimental results qualitatively.