喷射成形GH742y高温合金的高温变形特性

喷射成形是利用快速凝固方法制备高性能金属材料的先进的,低成本的净成形技术.本文研究了变形温度和应变速率对喷射成形GH742y高温合金热工艺塑性的影响.研究结果表明,喷射成形GH742y合金具有良好的热变形能力.不过,变形温度和应变速率对喷射成形GH742y合金的变形抗力也有较大的影响.     

TD-SCDMA系统的机遇与挑战

本文通过对TD—SCDMA系统的性能加以深入分析，并对其在网络规划中的特点与WCDMA系统进行比较，进一步加深对TD—SCDMA系统的认识。     

流域治理研究进展与我国流域治理体系框架构建

从流域治理协调机构、流域治理机制、流域治理法治化等3个方面对国内外流域治理进行了综述,并构建我国现代流域治理体系框架:建立全国性流域协调机构,实行流域集中统一治理,化解流域治理中的“集体行动困境”;推进流域治理法治化,完善以流域为单位的综合立法原则,健全整体性的流域治理法律法规内容,加强联合执法力度,促进立法、行政、司法的无缝对接,增强流域治理效能;树立山水林田湖草系统治理思维,建立流域整体化治理体制机制,促进流域治理多元化,推动区域一体化和部门协同化,实现流域治理的整体化、系统化。     

CuZnAl形状记忆合金母相时效过程中的组织变化

利用ρ-T曲线测量、X射线衍射、透射电镜观察等方法研究了Cu-19Zn-13A1(at％)合金母相时效过程中组织的变化规律。结果表明：Cu-19Zn-13Al合金母相时效时，口，母相发生了贝氏体转变，继续延长时效时间，贝氏体向α相转变；或者，由β1母相直接转变为块(棒)状的α相。Cu-19Zn-13Al(at％)合金母相时效时，Ms点先升高后下降，且分解过程进行较快，300min后分解过程基本上完成，合金不再发生马氏体相变。     

分子动力学模拟铜纳米团簇的结构稳定性

利用分子动力学研究了原子数为13～1 055的铜纳米团簇.结果表明:随着尺寸的减小,铜纳米团簇的结构发生晶体→非晶→晶体→非晶→晶体→非晶的转变.团簇平均原子结合能随着尺寸的减小而减小,且只依赖于短程有序,这说明了团簇平均原子结合能一般不能够作为非晶与密堆结构晶体转变的判据.平均原子间距不但依赖于团簇的尺寸,且对团簇结构的变化敏感,可以作为非晶与密堆结构晶体转变的一个判据.对偶分布函数的研究表明,大尺寸团簇的内部和表层原子结构都表现出晶格收缩效应,且不同于相应块体晶格,这表明了目前文献中关于团簇的块体加表面模型与壳核模型都有待改进.     

A free-cutting and ductile CuAlMnZnTiB shape memory alloy

The mechanical properties and cutting performance of the designed Cu Al Mn Zn Ti B shape memory alloy were studied by tensile test and microstructure observation. Using X-ray diffractometry, differential scanning calorimetry(DSC) and semi-quantitative shape memory effect test, the microstructure and shape memory effect were analyzed. It is found that lots of βphase and few α phase are formed in the quenching of Cu-7.5Al-9.7Mn-3.4Zn-0.3Ti-0.14B(mass fraction, %) alloy, a great deal of martensite and few α phase are formed in the aging alloy, while the annealing alloy is composed of a great deal of α phase and few βphase. The tensile strength and elongation of the annealed alloy are 649 MPa and 17.1%, respectively. Some tiny and dispersion distributed second phase particles are generated in Ti and B precipitates, greatly improving the alloy machinability.     

Cu-Al-Mn-Zn-Zr记忆合金的显微组织与力学行为

利用金相显微镜、透射电镜、扫描电镜观察和力学性能测试等手段研究了Cu—18．4A1—8．7Mn—3．4Zn—0．1Zr(摩尔分数，％)记亿合金(多晶)在不同温度与组织下变形时的力学行为。实验合金在不同温度下变形时延伸率不同，变形温度(Td)在Ms与Af之间时的延伸率小于变形温度(Td)高于Af时的延伸率。对实验合金施加应力时，最初的变形主要来自应力诱发马氏体，继而发生马氏体变体择优合并，二者对合金的变形都有贡献；变形量更大时，变体界面共格性被破坏，部分马氏体丧失热弹性。少量α相的析出不影响记忆效应，可使延伸率得以提高。     

Fabrication and properties of low oxygen grade Al2O3 dispersion strengthened copper alloy

The low oxygen grade Al2O3 dispersion strengthened copper alloy without hydrogen-fired expansion was fabricated by the technique of vacuum hot press and hot extrusion. The mechanical and electrical properties measurements and microstructures observation on as-hot extruded, as-cold drawn and as-annealed Cu-Al2O3 alloy were conducted. The results show that the addition of a suitable amount of boron in the alloy can lower the residual free oxygen content and then inhibit the hydrogen-fired expansion. The density, σb, σ0.2, hardness, δ and electrical conductivity of the alloy reach 8.86 g/cm^3 (relative density of 99.6%), 340MPa, 250MPa, HB95,24% and 93%(IACS) respectively after hot extruded with the extrusion ratio of 30:1. Its properties have no change after annealed at 900℃ for 1h. Its strength increases after cold drawing, while its ductility and electrical conductivity drop gradually. Various properties of the cold drawn alloy can recover to those of as-extruded after annealed at 900℃ for 1h without the occurrence of recrystallization.