【作者】 王晓冬；

【导师】 邢大伟；

【作者基本信息】 哈尔滨工业大学 ， 材料加工工程， 2008， 硕士

【摘要】 本文以铜模铸造法制备楔形非晶合金样品,以示差扫描量热仪(DSC)、扫描电镜(SEM)、X射线衍射仪为主要手段,分别研究了作为较大原子的Al、Ag对Zr-Cu二元合金结晶过程的干扰作用和规律,及作为小原子的Fe对Zr-Cu-Al与Zr-Cu-Ag三元非晶形成能力的影响。分析结果表明,具有较大原子半径的Al、Ag作为第三组元,对Zr-Cu二元共晶结晶过程有较强烈的干扰作用。具体表现为:1)试验中所采用的Zr-Cu-Al与Zr-Cu-Ag三元合金都具有较强的玻璃形成能力。2)在Zr-Cu-Al,及Zr-Cu-Ag合金楔形试样的结晶组织中,Al、Ag元素在领先析出的Zr-Cu相中的浓度较低,在领先相周围具有较高的浓度,说明Al、Ag元素通过在领先相析出的过程中发生溶质浓度再分配现象,从而对Zr-Cu金属间相的形成起着阻碍作用,这样从另一方面来说,提高了非晶形成能力。具有较小原子半径的Fe,作为Zr-Cu-Al与Zr-Cu-Ag三元合金的第四组元,虽然符合与其它原子半径相差超过12%的条件,但其添加的结果却是对上述两种合金系的结晶过程起到了促进作用,从而破坏了非晶形成能力。具体表现为:1)对于Zr-Cu-Ag合金来说,添加Fe后,由于Fe的原子半径较小,易于扩散,所以降低了Ag对Zr-Cu析出相的阻碍作用,从而促进ZrCu相的形成,进而引起整个体系结晶过程提前,破坏了非晶形成能力;2)对于Zr-Cu-Al合金来说,Fe的加入大大减低了楔形试样非晶区的大小。SEM分析表明,含Fe 5%的Zr-Cu-Al-Fe合金中在结晶前发生了相分离的现象,相分离的结果使得在过冷液相中形成了富Fe、Al区和富Cu区,在随后的冷却过程中,两个区域分别结晶,从而加速了整体的结晶过程。这样大大恶化了非晶形成能力。更多还原

【Abstract】 The fundamental questions related to the formation of a metallic glass, e.g., the disturbance and the frustration effect of the third component, such as Al or Ag,on the crystallization process of binary Zr-Cu alloy, and the glass forming ability deterioration caused by Fe addition to the ternary Zr-Cu-Al and Zr-Cu-Ag alloys have been studied by means of DSC, SEM, and XRD etc. in this dissertation.The results show that the third component, such as Al or Ag, which has a comparatively larger atomic radius, has a strong disturbance effect to the crystallization process of Zr-Cu alloy, thus lead to a good glass forming ability for the Zr-Cu-Al or Zr-Cu-Ag alloy. The reasons are as follows: i) fully glassy wedge ingots of the Zr-Cu-Al or Zr-Cu-Ag alloy with a diameter of over 5mm have been obtained by copper mould casting, showing a large glass forming ability of the two alloys. ii) the solute element redistribution of Al or Ag around the primary crystals of Zr-Cu phase in Zr-Cu-Al or Zr-Cu-Ag alloy has been found by means of SEM energy spectrum.The Fe element, which has a small atomic radius, have a deteriorate effect to glass forming ability when added as the fourth component into the Zr-Cu-Al or Zr-Cu-Ag alloy,though it has a atomic radius difference of more than 12% from other elements. For the Zr-Cu-Ag alloy, the addition of Fe leads to a in advance crystallization of the CuZr phase, which is probably due to that there is a positive mixing enthalpy between Fe and Cu. Thus, the glass forming ability of this Zr-Cu-Ag-Fe alloy is getting worse.For the Zr-Cu-Al alloy, the addition of Fe leads to a phase segregation in the liquid. Two different regions, one is rich in Fe and Al, and the other is rich in Cu, were found in the wedge ingot of Zr-Cu-Al-Fe alloy. Crystallization in the two different regions may occur easily, due to the deviation from the primary composition of Zr-Cu-Al alloy, which has a good GFA. So it is clear for the mechanism of the GFA decreasing by the Fe addition: it is due to the phase segregation in liquid by Fe addition.更多还原