![Masters Theses](../../assets/md5images/ebc0648ded2cd429f55e0a2fe4407546.gif)
Masters Theses
Date of Award
8-1996
Degree Type
Thesis
Degree Name
Master of Science
Major
Materials Science and Engineering
Major Professor
Charlie R. Brooks
Committee Members
Ben F. Oliver, R. A. Buchanan
Abstract
The Ni4Mo at.% Mo alloy, here referred to as Ni4Mo, is a single phase face-centered cubic structure (α) above 868oC; below this temperature it becomes long-range ordered (β). The conversion of α to βordering reaction) on cooling or by other heat treatment causes a marked increase (e.g., doubling) in the hardness and yield strength. However, extreme extreme embrittlement also occurs. A major purpose of the present study was to see if the addition of moderate amount of aluminum would prevent the embrittlement yet retain the strengthening during ordering. Aluminum was chosen because it might allow the alloys to retain the good corrosion resistance of Ni4Mo.
The alloys studied were the base Ni4Mo alloy and Ni4Mo with addition of 2, 5, 7, and 9 at.% aluminum. All samples were small arc melted buttons. They were solution heat treated at 1280oC for 50 hours in quartz tubes filled with argon, then quenched by breaking the tube under water. Samples were then aged at 600, 650, 700, 750, 850, and 950oC for up to 100 hours. Microhardness was measured and ductility was examined by bending thin slices. The microstructures were evaluated using optical, scanning electron and transmission electron microscopy. Corrosion resistance was evaluated using cyclic anodic polarization and polarization resistance testing.
A major finding was that aluminum increased considerably the hardness for all aging treatment and for all alloys (a maximum of about 650 HV after aging the 5, 7, and 9 at.% A1 alloys for 100 hours at 700oC), but did not prevent embrittlement. However, in the solution heat treated condition the hardness of the 9 at.% A1 alloy (440 HV) was approximately double that of the Ni4Mo alloy (220 HV), and good ductility was retained.
Recommended Citation
Shen, Ye-Lin, "Microstructural and Hardness Evaluation of Ni4Mo Alloy with Aluminum Additions. " Master's Thesis, University of Tennessee, 1996.
https://trace.tennessee.edu/utk_gradthes/3243