60NiTi合金的热压缩变形与显微组织演变

采用Gleeble-3500热模拟试验机对在变形温度500~650℃和应变速率0.001~1 s^(-1)条件下的60NiTi合金进行热压缩变形,分析其热变形行为和显微组织,建立变形本构模型,绘制热加工图。结果表明,当压缩温度升高或应变速率降低时,峰值应力减小。合金的热变形激活能为327.89 k J/mol,热加工工艺参数为变形温度600~650℃和应变速率0.005~0.05 s^(-1)。当变形温度升高时,合金的再结晶程度增大;当应变速率增大时,位错密度和孪晶数量增大,Ni3Ti相易于聚集;Ni3Ti析出相有利于诱发合金基体的动态再结晶。动态回复、动态再结晶和孪生是60NiTi合金热变形的主要机制。

多级形变热处理Cu-Ni-Co-Si-Cr-Mg合金的组织与性能

设计并制备一种高强度、中等导电性的Cu-1.3Ni-1.2Co-0.7Si-0.3Cr-0.1 Mg合金。研究多级形变热处理对合金组织和性能的影响及其强化机制。结果表明,在时效过程中,高密度位错区和亚晶界处析出大量纳米级的β-Ni_(3)Si、δ-(Ni,Co)_(2)Si和Cr相颗粒,凝固过程中形成亚微米级Cr_(3)Si相。该合金的抗拉强度、屈服强度和电导率分别为882 MPa、857 MPa和46.7%(IACS)。通过强化模型的计算和强度测试,该合金的主要强化机制为析出强化、应变强化和亚结构强化。

嵌入式铝/钢冷轧复合带材铝层的厚度波动形成机理与控制（英文）

研究压下率和铝带初始厚度对冷轧复合嵌入式铝/钢复合带材铝层厚度波动的影响,分析铝层厚度波动的形成机理,提出改善复合带材铝层厚度均匀性的措施。结果表明,随着压下率的增加,铝层厚度波动逐渐增大。当压下率低于40%时,初始铝带厚度对复合带材铝层厚度波动量的影响较小;当压下率高于40%时,随初始铝带厚度的减小,复合带材的厚度波动量增大。表面处理形成的钢带表面硬化层引起钢带表层变形和钢/铝界面结合程度不均匀是导致复合带材铝层厚度波动的主要原因。采用合适的钢带表面处理方式降低钢带表面硬化程度,改善钢带表层变形和钢/铝界面结合程度的均匀性,可有效降低铝/钢复合带材的铝层厚度波动。

Fe含量对Cu−Fe合金组织与性能的影响

采用真空热压法制备不同Fe含量的Cu−Fe合金坯料。研究Fe含量对热轧和时效处理Cu−Fe合金组织、力学性能和导电率的影响规律和机理。结果表明,当Fe含量<60%(质量分数)时,Cu相和Fe相动态再结晶程度增大;当Fe含量≥60%时,Cu相颗粒均匀分布在Fe相中,合金变形较均匀。随着Fe含量的增加,抗拉强度从Cu−5%Fe合金的305 MPa增加至Cu−70%Fe合金的736 MPa,其断后伸长率则从23%下降至17%,导电率从31%IACS下降至19%IACS。该结果对Cu−Fe合金的成分和加工工艺设计具有指导意义。

黄铜包纯铜绞线复合材料拉拔过程中横截面结构、显微组织和力学性能变化

对采用固/液连铸复合成形工艺制备的外径8.5 mm黄铜包覆纯铜绞线复合坯进行拉拔加工,研究拉拔过程中复合材料横截面结构、组织和力学性能的变化规律与变形机制。结果表明:复合坯具有良好的表面质量和冶金结合的黄铜/纯铜界面,断后伸长率达到53.1%。拉拔过程中,纯铜绞线与黄铜包覆层的协同变形程度较高。随着总变形量的增大,纯铜绞线发生塑性变形流入各纯铜线之间构成的三角弧形间隙区,当总变形量增大至50%时,三角弧形间隙区被纯铜填满。随着总变形量增加至63%,纯铜绞线内部先后产生位错胞、条状微晶带等组织;黄铜包覆层内部先后形成平面位错网、相互交叉的形变孪晶和切变带,主要变形机制依次为位错平面滑移、形变孪生和剪切变形机制。复合材料的抗拉强度由铸态的240 MPa增大到总变形量63%的519 MPa,而断后伸长率由铸态的53.1%降低到3.2%。"固/液连铸复合成形→拉拔"短流程加工方法可适用于制备高速铁路贯通地线用黄铜包覆纯铜绞线复合材料。

Ni含量对Cu−0.4Be合金时效组织和性能的影响

研究Ni含量(0~2.10%,质量分数)对Cu−0.4Be(质量分数,%)合金常规时效析出相、强度和导电率的影响,并分析影响机理。结果表明:添加Ni元素可促进强化相的析出,显著提高时效强化作用。当Ni含量由0增大到2.10%时,合金时效后的强度呈先增大后减小的变化趋势,在Ni含量为1.50%时达到最大;含1.50%Ni合金的峰值时效参数为400℃保温60 min,时效后合金的抗拉强度和屈服强度分别为611 MPa和565 MPa,分别是不含Ni合金的2.8倍和6.1倍;含Ni合金的导电率随着时效时间的延长而增加,但随着Ni含量的增大而下降。在400℃,随着时效时间的延长,Cu−0.4Be−1.5Ni合金发生γ″相→γ′相→γ相转变;当时效时间为60 min时,合金中出现大量弥散分布的纳米级共格γ″相和γ′相,析出强化作用显著,是合金具有较高强度的主要原因。

热冷组合铸型水平连铸Cu-0.36Be-0.46Co合金带材冷轧过程中显微组织和力学性能变化

采用热冷组合铸型(HCCM)水平连铸工艺制备300 mm(宽)×10 mm(厚) Cu-0.36%Be-0.46%Co(质量分数)合金带材,对连铸带材进行冷轧,研究轧制过程中合金显微组织和力学性能的变化规律与变形机理。结果表明:连铸带材具有沿长度方向的柱状晶组织,表面质量好,断后伸长率达到35%,无需表面处理可直接进行大变形冷轧加工,无中间退火的累积冷轧变形量达98%。当变形量较小时(20%),变形机理为位错滑移,形成大量弥散分布的位错和位错胞;当变形量为40%时,合金中出现形变孪晶,且孪晶与位错胞相互作用形成长条状位错胞;当变形量超过60%时,形成切变带,发生明显的微区晶体转动;随着变形量的进一步增大,切变带数量增多且相互作用,使晶粒明显细化。抗拉强度和硬度由铸态的353 MPa和HV 119分别升高至冷轧变形量95%时的625 MPa和HV 208,断后伸长率则由35%降低至7.6%。该结果可为发展铍铜合金带材HCCM水平连铸-冷轧短流程高效加工方法提供实验依据。

铜及铜合金作为免疫和抗菌元素的综述

讨论铜与人、细菌之间的关系。铜在人体免疫中发挥重要作用。在推荐摄入量下,铜可以增强人体的免疫防御反应。本文主要讨论铜的抗菌活性和抗菌机制。结论表明,铜的抗菌活性受细菌中铜稳态机制、粘附、湿度、菌株特异性以及抗菌剂制备方法的影响。对于颗粒抗菌和表面抗菌材料,讨论几种制备方法,如溶胶−凝胶法、冷喷涂法和生物合成法,分别属于化学合成、物理合成和生物合成法。溶胶−凝胶法有助于颗粒抗菌和表面抗菌材料的制备;冷喷涂技术可以应用于表面抗菌铜的合成;生物合成是一种可应用于纳米颗粒抗菌剂制备的新技术。

Liquid-solid interface control of BFe10-1-1 cupronickel alloy tubes during HCCM horizontal continuous casting and its effect on the microstructure and properties

Based on horizontal continuous casting with a heating-cooling combined mold （HCCM） technology, this article investigated the effects of processing parameters on the liquid-solid interface （LSI） position and the influence of LSI position on the surface quality, microstructure, texture, and mechanical properties of a BFe10-1-1 tube （φ50 mm × 5 mm）. HCCM efficiently improves the temperature gradient in front of the LSI. Through controlling the LSI position, the radial columnar-grained microstructure that is commonly generated by cooling mold casting can be eliminated, and the axial columnar-grained microstructure can be obtained. Under the condition of 1250℃ melting and holding temperature, 1200-1250℃ mold heating temperature, 50-80 mm/min mean drawing speed, and 500-700 L/h cooling water flow rate, the LSI position is located at the middle of the transition zone or near the entrance of the cooling section, and the as-cast tube not only has a strong axial columnar-grained microstructure （{hkl}〈621〉, {hkl}〈221〉） due to strong axial heating conduction during solidification but also has smooth internal and external surfaces without cracks, scratches, and other macroscopic defects due to short solidified shell length and short contact length between the tube and the mold at high temperature. The elongation and tensile strength of the tube are 46.0%-47.2% and 210-221 MPa, respectively, which can be directly used for the subsequent cold-large-strain processing.

Effects of Ni content on the cast and solid-solution microstructures of Cu-0.4wt% Be alloys

The effects of Ni content（0–2.1wt%）on the cast and solid-solution microstructures of Cu-0.4wt%Be alloys were investigated,and the corresponding mechanisms of influence were analyzed.The results show that the amount of precipitated phase increases in the cast alloys with increasing Ni content.When the Ni content is 0.45wt%or 0.98wt%,needle-like Be_（21）Ni_5 phases form in the grains and are mainly distributed in the interdendritic regions.When the Ni content is 1.5wt%or greater,a large number of needle-like precipitates form in the grains and chain-like Be_（21）Ni_5 and Be Ni precipitates form along the grain boundaries.The addition of Ni can substantially refine the cast and solid-solution microstructures of Cu-0.4wt%Be alloys.The hindering effects of both the dissolution of Ni into the matrix and the formation of Be–Ni precipitates on grain-boundary migration are mainly responsible for refining the cast and solid-solution microstructures of Cu-0.4wt%Be alloys.Higher Ni contents result in finer microstructures;however,given the precipitation characteristics of Be–Ni phases and their dissolution into the matrix during the solid-solution treatment,the upper limit of the Ni content is 1.5wt%–2.1wt%.

Effect of pre-annealing treatment on the microstructure and mechanical properties of extruded Al–Zn–Mg–Cu alloy bars

Taking extruded Al–Zn–Mg–Cu alloy(7A04 alloy) bars as the research object, the effect and mechanism of pre-annealing treatments on the microstructure and mechanical properties of the aged alloy bars were investigated. The results show that a pre-annealing treatment at 350°C for 15 h before a T6 treatment substantially reduced the sensitivity of the microstructure and mechanical properties of the extruded 7A04 aluminum alloy specimens toward the extrusion temperature. The average grain sizes of the specimens extruded at 390 and 430°C after T6 treatment were 3.4 and 8.1 μm, respectively, and their elongations to failure were 7.0% and 9.2%, respectively. However, after pre-annealing + T6 treatment, the differences in both the grain sizes and the elongations of the specimens became small, i.e., their average grain sizes were 3.2 and 3.8 μm and their elongations were 12.0% and 13.3%, respectively. For the specimens extruded at the same temperature, pre-annealing treatment obviously improved the plasticity of the alloy, which is attributed to an increase in soft texture or to grain refinement in the specimens as a result of the pre-annealing + T6 treatment.

Effects of Fe content on the microstructure and properties of CuN i10FeM n1 alloy tubes fabricated by HCCM horizontal continuous casting

Heating-cooling combined mold（HCCM） horizontal continuous casting technology developed by our research group was used to produce high axial columnar-grained CuN i10 FeM n1 alloy tubes with different Fe contents. The effects of Fe content（1.08wt%–2.01wt%） on the microstructure, segregation, and flushing corrosion resistance in simulated flowing seawater as well as the mechanical properties of the alloy tubes were investigated. The results show that when the Fe content is increased from 1.08wt% to 2.01wt%, the segregation degree of Ni and Fe elements increases, and the segregation coefficient of Ni and Fe elements falls from 0.92 to 0.70 and from 0.92 to 0.63, respectively. With increasing Fe content, the corrosion rate of the alloy decreases initially and then increases. When the Fe content is 1.83wt%, the corrosion rate approaches the minimum and dense, less-defect corrosion films, which contain rich Ni and Fe elements, form on the surface of the alloy; these films effectively protect the α-matrix and reduce the corrosion rate. When the Fe content is increased from 1.08wt% to 2.01wt%, the tensile strength of the alloy tube increases from 204 MPa to 236 MPa, while the elongation to failure changes slightly about 46%, indicating the excellent workability of the CuNi10FeMn1 alloy tubes.

Effect of continuous induction annealing on the microstructure and mechanical properties of copper-clad aluminum flat bars

Copper-clad aluminum （CCA） flat bars produced by the continuous casting-rolling process were subjected to continuous induction heating annealing （CIHA）, and the effects of induction heating temperature and holding time on the microstructure, interface, and mechanical properties of the fiat bars were investigated. The results showed that complete recrystallization of the copper sheath occurred under CIHA at 460℃ for 5 s, 480℃ for 3 s, or 500℃ for 1 s and that the average grain size in the copper sheath was approximately 10.0 μm. In the case of specimens subjected to CIHA at 460-500℃ for longer than 1 s, complete recrystallization occurred in the aluminum core. In the case of CIHA at 460-500℃ for 1-5 s, a continuous interracial layer with a thickness of 2.5-5.5 μm formed and the thickness mainly increased with increasing annealing temperature. After CIHA, the interracial layer consisted primarily of a Cu9A14 layer and a CuA12 layer; the average interface shear strength of the CCA flat bars treated by CIHA at 460-500℃ for 1-5 s was 45-52 MPa. After full softening annealing, the hardness values of the copper sheath and the aluminum core were HV 65 and HV 24, respectively, and the hardness along the cross section of the CCA flat bar was uniform.

Microstructure and texture evolution of Mg–3Zn–1Al magnesium alloy during large-strain electroplastic rolling

Large-strain deformation by single electroplastic rolling （EPR） was imposed on AZ31 magnesium alloy strips. During EPR at low temperature （150-250℃）, numerous twins formed in the alloy. After EPR at a high temperature （350℃）, the number of twins reduced and some dynamic recrystallization （DRX） grains formed at grain boundaries and twinned regions. The synergic thermal and athermal effects generated by electropulsing, which promoted dislocation motion, induced a few small DRX grains, and ductile bandings were mainly re- sponsible for large-strain deformation during EPR. The inclination angle of the basal pole stemmed from the counterbalance of the inclina- tion direction of the basal pole between the DRX grains and deformed coarse grains.

Effect of nitrogen on microstructure and secondary hardening of H21 die steel

The effect of nitrogen on the microstructure and secondary hardening of H21 die steel was studied by using scanning electron microscope, X-ray diffraction, transmission electron microscope and dilatometer. The results demonstrate that nitrogen can enhance the secondary hardening behavior of H21 hot-working die steel without toughness lose. Nitrogen addition increases the austenitic phase zone, decreasing austenite transformation temperature and martensite transformation temperature, thereby increasing the retained austenite stability. Retained austenite in quenched steel can dissolve a large quantity of alloy, thereby decreasing the coarsening rate of the precipitates. Trace nitrogen could intensify the refinement of pearlite by decreasing the diffusion rate of alloying element into carbides. Nitrogen increases the amounts and precipitation temperature of the undissolved V(C, N) and suppresses the growth of prior austenite before quenching. During tempering process, parts of nitrogen in V(C, N) dissolved back into the matrix, resulting in the distorting lattice of ferrite, thereby reinforcing the matrix. Meanwhile, the solid-dissolved nitrogen inhibits the growth of carbides by decreasing the diffusion rate of alloying elements.