熔体处理对过共晶铝铁合金富铁相的影响

经电流处理或热速处理后的过共晶铝铁合金组织中初生富铁相得到细化 ,由粗大的板块状变为花朵状和针点状。由于组织得到细化 ,力学性能也得到了相应提高。此外 ,还对电流处理和热速处理的细化机理作了分析。

镁对过共晶铝铁合金组织形貌的影响

针对普通熔铸条件下过共晶Al-Fe合金初生富铁相严重割裂基体、恶化合金性能的问题,采用元素Mg对过共晶Al-5%Fe合金进行变质细化处理,Mg以Al-10%Mg中间合金形式加入。借助光学显微镜等分析了Al-10%Mg中间合金晶粒细化剂加入量和熔体保温时间对过共晶Al-5%Fe合金微观组织形貌及性能的影响。试验表明:在过共晶Al-5%Fe合金中加入Al-10%Mg中间合金细化剂,当加入量为1.2%、保温时间90min时,细化效果较好,Al-5%Fe合金中初生A13Fe相由未添加细化剂时的粗大板条状变为花朵状和颗粒状,并且尺寸明显减小,从而显著提高材料的强度和塑性。

钪锆复合对过共晶铝铁合金的强化效果

过共晶铝铁合金中复合添加微量钪锆元素,初生Al3Fe相和铝基体相形貌改变,合金组织得到细化。合金的抗拉强度达到了142MPa,与未加钪锆元素的二元Al-6%Fe合金相比有了显著提高,而且伸长率也有细微提高。探讨了微量钪锆复合对过共晶铝铁合金的强化效果机理。

微量元素Sc和Zr对过共晶Al-5%Fe合金组织和性能的影响

二元过共晶Al-5%Fe合金中的初生Al3Fe相为粗大的针片状。微量元素Sc和Zr加入到过共晶Al-5%Fe合金中,合金的初生Al3Fe相形貌发生显著变化。其细化作用在Sc、Zr加入量分别为0.3%和0.1%时效果较好,合金的初生Al3Fe相转变为细小的针状、粒状和花朵状。合金的抗拉强度达到266.8 MPa,提高了119.8%。讨论了Sc、Zr联合添加对过共晶Al-5%Fe合金初生Al3Fe相的作用机理。

精炼温度对过共晶Al-5Fe合金中富铁相形貌的影响

研究了在不同温度下C2 Cl6精炼对过共晶Al 5Fe合金中富铁相形貌的影响。结果表明 ,在较高的精炼温度下 ,合金中富铁相形态由长针片状转变为花朵状或颗粒状 ,且在 95 0℃精炼时得到基本上为细小颗粒状均匀分布的组织 ,合金抗拉强度也有了明显改善。并对精炼工艺对合金组织的改善作用进行了分析。

Al-Fe二元合金共晶组织的数值模拟

在考虑温度梯度对共晶生长的影响并假设固液界面为曲面的基础上,建立了与时间相关的层片共晶生长的自调整模型,采用有限差分法进行了数值求解。对含2％Fe的共晶Al—Al3Fe组织的平均层片间距进行了数值模拟,计算出了固液界面前沿的浓度场分布。采用定向凝固试验验证了模拟结果的正确性。

Effect of ultrasonic vibration on Fe-containing intermetallic compounds of hypereutectic Al-Si alloys with high Fe content

The Fe-containing intermetallic compounds with high melting point in hypereutectic Al-Si alloys can improve the heat resistance and wear resistance at elevated temperatures. However, the long needle-like Fe-containing compounds in the alloys produced by conventional casting process are detrimental to the strength of matrix. The effect of ultrasonic vibration （USV） on the morphology change of Fe-containing intermetallic compounds in the hypereutectic Al-17Si-xFe （x=2, 3, 4, 5） alloys was systematically studied. The results show that, the Fe-containing intermetallic compounds are mainly composed of long needle-like β-Al5FeSi phase with a small amount of plate-like δ-Al4FeSi2 phase in Al-17Si-2Fe alloy produced by conventional casting process. With the increase of Fe content from 2% to 5% in the alloys, the amount of plate-like or coarse needle-like δ-Al4FeSi2 phase increases while the amount of long needle-like β-Al5FeSi phases decreases. In Al-17Si-5Fe alloy, the Fe-containing intermetallic compounds exist mainly as coarse needle-like δ-Al4FeSi2 phase. After USV treatment, the Fe-containing compounds in the Al-17Si-xFe alloys are refined and exist mainly as δ-Al4FeSi2 particles, with average grain size ranging from 26 μm to 37 μm, and only a small amount of β-Al5FeSi phases remain. The mechanism of USV on the morphology of Fe-containing intermetallic compounds was also discussed.