Effect of Heattreatment on Directionally Solidified NB Containing Tlalallys

作     者：Getman Anton 

作者单位：哈尔滨工业大学 

学位级别：硕士

导师姓名：Ruirun Chen

授予年度：2013年

学科分类：080503[工学-材料加工工程] 08[工学] 080502[工学-材料学] 0805[工学-材料科学与工程（可授工学、理学学位）] 0802[工学-机械工程] 080201[工学-机械制造及其自动化] 

主      题：direction solidification grain size lamelae spacing TI-46Al-6Nb Ti-46Al- 6.3Nb-0.1B compressive stress 

摘      要：This paper talks about the effect of heat treatmant (HT) on the cast and direction solidified (DS) Ti-46Al-6Nb and Ti-46Al-6.3Nb-0.1B compositions. These materials were prodused by cold crucible electromagnetic process. Samples were heat treated with six different conditions with the Muffle Atmosphere Furnace XY-1600A. HT1: temperature at1270℃for2h+air cooling. HT2:temperature at1330℃for2h+air cooling. HT3:temperature at1330℃for2h+900℃for30min+air cooling. HT4: temperature at1330℃for2h+air cooling, and then was repeat heating at1330℃for10min. HT5:temperature at1330℃for10min+air cooling, and then was repeated the same HT process. HT6:temperature at1330℃for10min+air cooling, and then was repeated the same HT process four times. After HT process all samples were polished, etched and prepared for further analysis. Firstly samples were taken pictures by a digital camera. Analysis of microstructure was performed by the optical microscope (OM) and the scanning electron microscope (SEM). After microstructure analysis all samples were cut into several small cylinders for compressive stress (CS) tests. CS test were tested by Inston5960Dual Column Tabletop Universal Testing Systems. Analysis of fracture mechanism before and after heat treatment was done by SEM. HT1decreased of average grain size of cast alloy from1.4mm to0.3mm, but didn t change the grain morphology of DS samples. Also HTlincreased of the lamellar spacing from2.46μm to4.38μm. The compressive stress decreased after HT1. HT2-HT4had insignificant influence on changing average grain size macrostructure of cast materials, but cardinally changed morphology and microstructure of DS materials. HT2-HT4and HT6caused elimination of all segregations. HT2-HT6decreased the lamellar spacing. The best result of compressive stress property had showed HT5. Also HT5caused the smallest lamellar spacing. HT1and HT2changed fracture mechanisms a little, but HT5and HT6significant changed fracture mechanism from inter or trans-lame