真空熔炼、氩气保护连续定向凝固技术

阐述了真空熔炼、氩气保护下引法连续定向凝固工艺.该工艺将真空感应熔炼和连续定向凝固技术结合在一起,集熔化、提纯、凝固于一体,控制方便,搅拌、脱氧能力强,生产效率高,能生产纯净度高、性能好的定向凝固材料.对该工艺生产的纯铜棒材的质量进行了分析.     

Fabrication of Unidirectional Fibrous Crystal Reinforced Super High Strength Steel Wire

提出了将连续定向凝固技术与低温强塑性加工相结合,制备连续纤维晶强化超高强度钢丝的思想,并在实验室成功地制备了具有单向柱状晶组织的铸铁与不锈钢铸棒,证实了连续定向凝固技术用于钢铁材料是可行的。     

连续定向凝固过程铜铬合金的组织与缺陷

研究了铜铬合金的连续定向凝固的工艺条件及相互之间的匹配关系,以及铜铬合金的显微组织及其表面缺陷形成的成因,结果表明,结晶器高度１０－２５ｍｍ,冷却距离２５ｍｍ,合金温度１２１０－１２８０℃,牵引速度０．２－１．０ｍｍ／ｓ,冷却水量７２０Ｌ／ｈ时,可制得Ｃｕ－０．６％Ｃｒ合金材料。     

铜单晶体冷轧形变微观组织结构

研究金属材料塑性变形的滑移模式及微观组织结构的演变过程。利用电子背散射衍射(EBSD)技术,表征了铜单晶体的形变微观组织结构。在不同的应变量下,铜单晶体的形变微观组织结构存在着明显的差别。低应变量(20%)下,其形变微观组织结构主要是高密度位错墙;应变量增高至50%时,其形变微观组织结构中还出现了微带、位错胞及位错胞块。不同应变量下的微观组织结构的差异,主要由不同的形变阶段,晶体的滑移模式不同造成。     

SiC单晶线锯切片及电镀锯丝制造技术的研究进展

针对碳化硅(SiC)单晶硬度高、脆性大,金刚石线锯切片时工具磨损快、切割效率低、晶片表面亚表面易出现微破碎损伤,使SiC单晶高质量切片和高性能锯丝制造技术成为关键和难点的状况,综述了SiC单晶线锯切片及电镀金刚石锯丝制造技术的研究现状,对其中存在的问题进行了概括与分析,并提出了SiC单晶金刚石线锯切片技术的未来研究方向。     

Effect of Mo content on microstructure and stress-rupture properties of a Ni-base single crystal superalloy

The additional 1.5 wt% Mo was added in a Ni-base single crystal(SC) alloy with the composition of Ni–6.5Al–8.0Mo–2.4Cr–6.2Ta–4.9Co–1.5Re–(0.01–0.05)Y(wt%) to study the effect of Mo content on the microstructure and stress-rupture properties. The creep and stress-rupture tests under the conditions of 850 °C/500 MPa and 1100 °C/130 MPa were conducted, and the microstructure of as-cast, heat treated and stress ruptured specimens were analyzed. It was found that the 1.5 wt% Mo addition enhanced the stress-rupture lives at both intermediate(850 °C) and high(1100 °C)temperatures. The microstructure analysis showed that adding 1.5 wt% Mo in the basic alloy affected the microstructure dramatically, i.e., the Mo-rich phases formed in the specimens of as-cast and stress-ruptured specimens. It is considered that the improvement of the stress-rupture lives is duo to the strengthening effect of Mo to both γ and γ'phases and the decrease of stacking fault energy, diffusion constant and dislocation spacing. The Mo-rich phases precipitated under condition of 1100 °C/130 MPa did not affect the creep and stress-rupture properties obviously in the present study.     

Effects of Mo addition on microstructure of a 4th generation Ni-based single crystal superalloy

The effects of Mo addition on the microstructure of a 4th generation Ni-based single crystal superalloy were investigated. Mo addition significantly promoted elements Mo, W and Re partition into γ phase and enhanced absolute lattice misfit at 1100 ?°C. The increase of Mo concentration from 2 ?wt% to 4 ?wt% also decreased the content of eutectic islands and the segregation ratios of other alloying elements in the as-cast state, especially Re and W. After heat treatments, the size of γ′ phase and width of γ channels decreased slightly with higher Mo content. More Mo additions slightly enhanced the segregation behavior of Re while reducing the segregation behavior of Mo. However, it revealed that the primary and secondary dendrite arm spacings were barely affected by Mo addition.     

硼对第二代镍基单晶高温合金显微组织的影响

硼(B)是强化镍基单晶合金小角度晶界的重要微量元素,但目前关于B对镍基单晶合金显微组织影响的系统报道非常有限。通过对3种不同B含量(质量分数分别为0、0.01%、0.02%)的第二代镍基单晶合金DD11铸态及热处理态组织定量表征,研究了B对相转变温度、(γ+γ′)共晶组织、硼化物的影响。结果表明:B显著降低合金的固液相线,提高铸态共晶组织体积分数;0.01%B的加入,合金中未出现M3B2型硼化物相;而0.02%B的加入,显著促进了骨架状硼化物的形成,降低合金初熔点,引起残余共晶含量的大幅度提高;骨架状硼化物吸收较多的Cr、Mo和W等元素,降低合金的固溶强化效果,可导致单晶合金基体的蠕变性能大幅度降低。研究结果对认识单晶合金中微量元素B的作用机理及优化B成分范围具有理论指导意义。     

应力时效对镍基单晶合金DD11组织及持久性能的影响

研究了1070℃/100MPa应力时效对镍基单晶合金DD11组织和持久性能的影响,通过扫描电镜和透射电镜对应力时效前后的组织进行了观察和分析,并对合金应力时效前后的持久性能进行了测试与分析。实验结果表明:应力时效前50h是形筏阶段,竖直方向的γ相通道逐步变窄或消失,水平方向的γ相通道宽度逐步增加,立方状γ′相在应力的作用下向水平方向扩展并相互连接在一起逐渐形成筏排形貌。应力时效50h后是筏排粗化阶段,随应力时效时间的延长,组织缓慢粗化,但是筏排形貌基本保持稳定。对应力时效后的组织进行1 070℃/140 MPa持久性能测试,结果表明,在形筏阶段持久寿命基本保持稳定,在筏排粗化阶段,持久寿命逐步下降。应力时效500h后,持久寿命由热处理后初始状态的360h左右降低至140h左右。研究结果表明,γ相通道尺寸的粗化和组织的筏排化是持久性能衰退的主要因素。