低碳钢超细晶铁素体的形成

将含碳量(质量分数)为0．057％和0．18％的低碳钢在不同过冷度、变形温度、变形速率和变形量的条件下进行热模拟实验,研究了含碳量和热变形条件对超细晶粒形成的影响．结果表明,变形前快速冷却(20℃／s)至Ar3以上附近温度并进行超过50％变形量的变形,能强烈促进过冷奥氏体形变诱发铁素体相变,铁素体在奥氏体(?)内平行的变形带上形核,并发生动态回复和再结晶,从而使组织细化．形变诱发的相变过程由碳的扩散所控制,当钢的含碳量比较高时,小过冷度、大变形量和中等变形速率有利于铁素体相变,晶界碳化物的析出能够抑制铁素体晶粒的长大,因而高碳含量钢表现出更好的细化晶粒效果．

低、中碳钢材料高温化学抛光工艺

低、中碳钢材料低温化学抛光过程中双氧水易分解、温度不易控制、中温化学抛光配方中使用氢氟酸的废水中氟离子较难处理 ,为了解决这些问题研究了高温化学抛光液的组成和前处理工艺 ,分析了抛光液中各物质含量对工件产生的影响。结果表明 ,在不使用CrO3 的情况下 ,将普通酸和常用助剂组合 ,温度控制在 95～ 110℃时 ,可以使低、中碳钢工件表面抛光成镜面光亮 ,抛光时间短、速度快、效率高、容易控制、无有毒气体NOx 逸出 ,废水中无有毒离子 ,可以实现清洁化生产。

镍在低碳钢表面的扩散机理与规律

采用水溶液电沉积+高温固态扩散法成功制备了镍/低碳钢表面复合材料,研究了镍在低碳钢表面的扩散机理,利用Den Broeder法得到了不同温度下镍在低碳钢中的扩散规律。结果表明,高温固态扩散退火处理实现了镍沉积层与低碳钢的冶金结合,镍原子主要沿低碳钢晶界进行扩散,其扩散抑制了晶粒的长大。碳、硅、锰、硫、磷原子对镍原子的扩散影响较小。镍原子在低碳钢表面的固态扩散规律为D_(Ni)=-3.53×10^(-21)T^(4)+1.75×10^(-17)T^(3)-3.22×10^(-14)T^(2)+2.60×10^(-11)T-7.81×10^(-9)。在973~1373 K温度区间固态扩散时,随着温度的升高,镍原子的平均互扩散系数呈现先上升后下降再上升的趋势;晶体结构对于镍原子的扩散影响较大,镍原子在体心立方晶体结构中的扩散速度明显大于在面心立方晶体结构中的扩散速度。

热变形参数对奥氏体再结晶过程的影响

利用热模拟压缩变形试验 ,对低碳钢在热变形过程中应变速率、应变量和形变温度对奥氏体晶粒度的影响进行了研究 。

Fabrication of cast carbon steel with ultrafine TiC particles

The carbon steels dispersed with ultrafine TiC particles were fabricated by conventional casting method. The casting process is more economical than other available routes for metal matrix composite production, and the large sized components to be fabricated in short processing time. However, it is extremely difficult to obtain uniform dispersion of ultrafine ceramic particles in liquid metals due to the poor wettability and the specific gravity difference between the ceramic particle and metal matrix. In order to solve these problems, the mechanical milling (MM) and surface-active processes were introduced. As a result, Cu coated ultrafine TiC powders made by MM process using high energy ball milling machine were mixed with Sn powders as a surfactant to get better wettability by lowering the surface tension of carbon steel melt. The microstructural investigations by OM show that ultrafine TiC particles are distributed uniformly in carbon steel matrix. The grain sizes of the cast matrix with ultrafine TiC particles are much smaller than those without ultrafine TiC particles. This is probably due to the fact that TiC particles act as nucleation sites during solidification. The wear resistance of cast carbon steel composites added with MMed TiC/Cu-Sn powders is improved due to grain size refinement.

Si含量对轧制复合铝钢层状复合材料界面化合物组织形貌的影响

通过在铝中添加合金化元素Si,并对轧制复合铝合金/低碳钢双层复合材料进行不同温度和时间的退火,借助金相显微镜、扫描电镜和EDAX能谱仪,研究Si对轧制复合钢界面化合物生长行为的影响规律。结果表明,在Si含量为0.67wt%时,生成复合界面金属间化合物的临界温度达到615℃,此时Si对抑制界面化合物生成的效果最好;Si含量超过1.62wt%后,Si降低了Al-Si合金的熔点,使Al侧元素的扩散速率增加,促进了复合界面金属间化合物的长大,化合物的组成为τ6-Al8Fe2Si+τ5-Al4.5FeSi+η-Al5Fe2。