ABSTRACT
Titanium Grade 38 (Ti-4Al-2.5V) has good cold-workability and exhibits relatively high ductility similar to Titanium Grade 9 (Ti-3Al-2.5V), but has strength properties approaching that of Titanium Grade 5 (Ti-6Al-4V). Grade 38, which was originally developed for industrial and armor applications, has higher strength than most other titanium grades and can be used in higher temperature applications up to 600 °F.
Results of crevice corrosion, U-bend, and general corrosion tests in various different media are discussed in this paper. These tests were conducted in order to better understand how Grade 38 compares to common titanium alloys. The alloys included in this comparison were:
ASTM Grade 2 Titanium, UNS R50400
ASTM Grade 5 Titanium, UNS R56400
ASTM Grade 9 Titanium, UNS R56320
ASTM Grade 12 Titanium, UNS R53400
ASTM Grade 38 Titanium, UNS R54250
The unique combination of high strength, ductility, formability, workability, and corrosion resistance gives Grade 38 versatility in a wide variety of applications.
INTRODUCTION
The ATI 425 ? (1) titanium alloy, to be referred to as Grade 38, a proprietary alloy, was originally developed in the late 1990â??s by Dr. Kosaka for hot-rolled armor plate. The alloy was intended as a lower cost formulation which could utilize recycle streams with higher oxygen and iron contents.1, 2 The increased iron is used as a beta stabilizer and allows for the replacement of some of the higher priced vanadium.303E Table 1 shows the normal alloy chemistry of Grade 38 as well as other common titanium grades.
TABLE 1
NORMAL ALLOY CHEMISTRY OF COMMON TITANIUM GRADES (available in full paper)
It was discovered during preparation of plate samples for ballistics testing, that Grade 38 had very good hot workability. This allowed a more lenient window for processing than necessary for Grade 5. Grade 38 flowed easier in forging and rolling, was less prone to surface cracking, and required less surface conditioning for subsequent working than did Grade 5. It was also discovered that Grade 38 had the ability to be cold worked similar to Grade 9, even with oxygen levels higher than that of Grade 9. 4 All forms of Grade 38 tested showed mechanical properties similar to Grade 5 but had the added advantage of being easier to form. Table 2 shows the mechanical properties of Grade 38 as compared to other common titanium grades. 1
TABLE 2
MECHANICAL PROPERTIES OF COMMON TITANIUM GRADES (available in full paper)
During initial alloy development, it was understood that armor plate could potentially be exposed to chlorides in a marine environment. One concern was the higher iron content and its effect in the presence of these chlorides. Initial seawater and hot salt cracking tests were performed and Grade 38 showed results similar to Grade 5. No further testing was deemed necessary as the only applications at that time were for amphibious vehicles, shipboard applications, and the potential to be used in some aircraft components. 4
This content is only available via PDF.
