铜合金高温相变分析论文铜合金高温相变分析论文.doc

Sn-Bi-Pb合金熔体结构转变对凝固行为及组织结构影响 摘要： 近年来的研究不断发现，很多合金熔体在熔点以上一定温度范围内会发生温度诱导的非连续液-液结构转变.实践表明液态结构的研究对材料成型及材料加工具有积极的意义,通过直流四电极法，我们得出了电阻率温度曲线，由曲线图分析，在加热过程中，Sn-Bi-Pb合金在762℃—965℃摄氏度范围内电阻率有明显的变化。本文是以Sn-Bi-Pb合金为例，研究合金熔体结构转变对凝固行为及组织结构影响。 实验是在直流四电极测电阻率实验的基础上，我们做凝固实验，实验首先是制作两个同样成分的合金试样（Sn50Bi40Pb），其中一个试样加热到680℃，保温一小时，然后在空气中缓慢冷却；另外一个加热到1000℃，在随炉冷却到680℃，从加热炉中取出后在空气中冷却。将制作好的两个试样打上标签，接下来进行研磨、腐蚀。最后进行金相观察、对比。 通过实验我们发现，结构转变之后熔体的凝固行为和凝固组织与结构转变之前相比有很大区别，晶粒尺寸有明显的变化，进一步分析表明，发生液-液结构转变的合金，过冷度有明显的增加。通过硬度实验，我们进一步验证发生液-液结构转变的合金，硬度有所增加。 关键词：液---液结构转变；凝固组织；过冷度；直流四电极法 Abstract ：In recent years, it has been found that many alloys’ melt experienced temperature-induced discontinuous L-L structure transition at a certain temperature above liquidus. Practice shows that researches in alloys’ melt of the liquid structure have a positive impact on material forming and manufacturing process.By means of D.C. four-probe method we had knew the resistivity-temperature curve，during the Heating process, the resistivity of Sn-Bi-Pb alloys have a great chang during 762℃-965℃.Bying study Sn-Bi-Pb alloy,We know liquid-liquid structural transformation has great effect on solidification behavior and solidified structures. Solidification experiment is based on the D.C. four-probe method, First, we made two productions of alloy components of the same sample（Sn50Bi40Pb）， One specimen heated to 680 ℃, Holding one hour, And then slow cooling in the air; another heated to 1000 ℃, in the furnace cooling to 680 ℃. Removed from the furnace in the air after cooling,We will create a good sample bear two labels, Then a grinding, corrosion.Finally, observat organization, comparison. Experimental results show that before and after structural changes the melt solidification behavior and solidification structures are quite different. Grain size significantly changed,Further analysis showed that undercooling of the l-l alloy has increased significantly, Through the experiment of hardness,We further verification that A l-l alloy