Effect of Powder Particle Size on Microstructure and Mechanical Property of Ni-Based P/M Superalloy Product

The solid sintering behavior and mechanical properties of Fe Ni powders prepared by mechanical alloying of elemental powders and hot pressing sintering in vacuum atmospheres were investigated. It was observed that the microstructure of the powder particles evolves in three stages. The alloy powder with average grain size of 20-30 nm was obtained. The sinter densification depends crucially on the particle rearrangement and the large amount of internal strain introduced during milling. The theoretical density of over 95 % was obtained after hot pressing sintering at 800 ℃ for 30 min with pressure of 50 MPa. No significant grain growth was observed during sintering. And also relatively high hardness was obtained.

基于图数据库的装备信息联想式查询

在院校、部队教学和训练中,常常需要对武器、装备的相关信息进行查询、比较,这类系统传统上是通过关系数据库技术实现的.但是,由于装备种类之间的差异太大,没有一个共同的"数据模型"可用;另外,关系数据库对于装备之间的"联系"处理起来相当困难,本文提出了基于图数据库的装备信息"联想式"查询,较好地解决了这些问题.

H13钢中富钒初生碳化物的形成及影响因素

大尺寸初生碳化物是H13钢冲击性能降低的重要原因,利用光学显微镜、扫描电镜和电子探针等分析碳化物的成分、尺寸分布及形貌。结合热力学和偏析模型分析了H13钢中不同类型的VCx碳化物生成条件以及活度对碳化物生成的影响。结果表明,液相线及以上不能生成VCx碳化物,枝晶间钒、碳元素的偏析是凝固过程碳化物生成的直接因素。VC（0.88）是最容易生成的富钒碳化物,在两相区生成,而V2C可通过共晶反应生成。碳化物尺寸与元素偏析程度、析出临界固相率及枝晶尺寸等有关。通过调整初始钒、碳元素质量分数及凝固冷却条件可以控制H13中的VC（0.88）的生成,当初始元素质量分数满足w（[V]0）≤0.6%、w（[C]0）≤0.37%时,钢中富钒碳化物生成受到抑制,对于开发新型无碳化物热作模具钢有指导意义。