Method for producing vanadium-aluminum-ruthenium master alloys and master alloy compositions

Vanadium-aluminum master alloys with small amounts of refractory metals such as ruthenium, are made substantially free of refractory inclusions and with a substantially homogeneous microstructure by reacting vanadium oxides with excess aluminum through an aluminothermic reduction reaction in the presence of the refractory to yield the desired master alloy. A preferred homogeneous vanadium-aluminum-ruthenium alloy without inclusions contains from about 59 to 70% of vanadium, about 29 to 40% of aluminum, and about 1 to 10% of ruthenium, all based on the weight of the alloy. The substantially homogeneous and inclusion-free master alloy is then used to produce titanium base alloys of higher quality, such as 4% vanadium and 6% aluminum titanium base alloys containing small amounts of refractory metals, usually containing from about 0.1 to 1.0% of ruthenium.

FIELD OF THE INVENTION 
The invention relates to titanium base alloys, and more particularly to 
vanadium-aluminum master alloys containing small amounts of refractory 
metals, such as ruthenium, which are suitable for further alloying into 
titanium base alloys. The invention also relates to methods for producing 
vanadium-aluminum master alloys containing refractory materials, such as 
ruthenium, which are useful in providing titanium base alloys containing 
refractory materials of greater homogeneity. 
BACKGROUND OF THE INVENTION 
Titanium metal and titanium base alloys are lightweight, relatively strong 
metals, with high heat and corrosion resistance. These materials are in 
great demand today as preferred materials for use in aircraft, spacecraft 
and military applications. Titanium base alloys, such as those which 
contain 4% vanadium and 6% aluminum, are used, for example, in the blades 
of jet propulsion engines for aircraft by reason of their high strength in 
both hot and cold environments, and their resistance to oxidation and 
corrosion. 
In the past, such 4% vanadium and 6% aluminum titanium base alloys have 
generally been prepared from vanadium-aluminum master alloys, particularly 
those containing 65% vanadium and 35% aluminum. In order to minimize the 
quantity of contaminants, interstitials and inclusions in the final 
titanium base alloy, considerable effort has been given to producing 
vanadium-aluminum master alloys of the highest purity. 
Vanadium-aluminum master alloys, such as the 65% vanadium and 35% aluminum 
alloy, can be prepared by aluminothermic reduction of vanadium pentoxide 
in the presence of a molten flux. During the reaction, vanadium pentoxide 
is reduced by aluminum as the reducing agent to pure vanadium metal which 
alloys with aluminum present in excess of that required for the reduction. 
Alumina is formed as slag, and enters the molten flux which floats on the 
top of the alloy. The thermite reaction is highly exothermic and 
self-propagating once ignited. 
U.S. Pat. No. 3,625,676 (Perfect) discloses an improved vanadium-aluminum 
master alloy from which titanium base alloys can be prepared, such as 
those which contain 4% vanadium and 6% aluminum. The master alloy, for 
example containing about 40% vanadium, 60% aluminum and small amounts of 
titanium, yields an alloy free of slag voids and gross nitride inclusions 
and results in improved physical properties and greater soundness in the 
titanium base alloy. The vanadium-aluminum-titanium master alloys of 
Perfect are prepared by aluminothermic co-reduction of vanadium pentoxide 
and titanium dioxide in the presence of excess aluminum and a molten flux. 
The vanadium-aluminum master alloy thereby produced includes from about 40 
to 55% vanadium, from about 60 to 40% aluminum, and from about 0.5 to 5% 
titanium. U.S. Pat. Nos. 2,789,896 (Coffer); 4,256,487 (Bobkova, et al.); 
and 5,002,730 (Fetcenko) disclose other methods for producing 
vanadium-containing alloys by metallothermic reduction of vanadium oxide 
to vanadium metal. 
Use of a vanadium-aluminum master alloy in the production of titanium base 
alloys has been proved desirable in obtaining substantially complete 
dissolution of the higher melting point vanadium in the lower melting 
point titanium base metal. Vanadium is reported to have a melting point of 
1,890.degree. C., as compared to the melting point of 1,660.degree. C. for 
titanium. The vanadium-aluminum master alloy forms a eutectic with a lower 
melting point than vanadium and which more readily dissolves in the 
titanium base metal, and forms a base alloy free of vanadium inclusions. 
In the past such 4% vanadium and 6% aluminum titanium base alloys have also 
included small amounts of refractory materials, such as ruthenium. These 
alloys have generally been prepared by blending ruthenium in the final 
base alloy charge containing the vanadium-aluminum master alloy and 
titanium sponge. The final titanium base alloy is formed by vacuum, 
consumable-electrode arc melting. However, in the production of such 
titanium base alloys with refractory ruthenium, difficulties have been 
encountered in obtaining complete dissolution of the substantially higher 
melting point ruthenium metal in the titanium base metal, which has a much 
lower melting temperature. Ruthenium is reported to have a melting point 
of 2,310.degree. C., as compared to the melting point of 1,660.degree. C. 
for titanium. As a result of this incomplete dissolution, ruthenium 
particles, which have a specific gravity of 12.5, as compared to 4.5 for 
titanium, segregate and drop, in unmelted form, to the bottom of the 
molten titanium pool, and form inclusions in the ingot produced. 
Complete dissolution of ruthenium and/or other refractory metals in the 
titanium base alloy is highly desirable, because a single undissolved, 
sizable inclusion of the refractory metal in the alloy ingot may make the 
ultimate alloy unfit for many possible uses. The inclusions carry over 
through remelts as well, so that the ultimate alloy and products produced 
from it contain inclusions. Such inclusions in a finished article subject 
to mechanical stress, such as the blades of an aircraft jet propulsion 
engine, have a stress raising character, and could cause the part to crack 
or rupture catastrophically. 
What is needed is a method of producing a homogeneous, inclusion free, 
vanadium-aluminum master alloy including small amounts of refractory 
metals such as ruthenium, which is suitable for alloying with titanium to 
produce a titanium base alloy. What is further needed is a method of 
producing a titanium base alloy containing refractory metals such as 
ruthenium, which have a homogeneous microstructure, are free of refractor 
inclusions and are made from an inclusion free, homogeneous 
vanadium-aluminum master alloy containing refractory metals. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide master alloys 
containing vanadium and aluminum, and also refractory metals such as 
ruthenium, which are substantially free of refractory inclusions and are 
suitable for subsequent alloying into substantially homogeneous titanium 
base alloys. 
It is another object of the present invention to provide a method for 
preparing substantially homogeneous vanadium-aluminum master alloys 
containing refractory metals such as ruthenium, for use in preparation of 
titanium base alloys containing refractory metals, without requiring 
expensive apparatus or materials, while resulting in master alloys and 
final alloys of excellent quality and yields. 
It is yet another object of the present invention to provide a method of 
producing titanium base alloys containing refractory metals free of 
refractory inclusions. 
It is still another object of the present invention to provide a method of 
obtaining substantially complete dissolution and/or distribution of 
refractory metals, such as ruthenium, in titanium base alloys. 
The present invention resides in a method for producing a 
vanadium-aluminum-ruthenium master alloy which is substantially 
homogeneous and free of ruthenium inclusions, which includes the steps of: 
(a) mixing together a powdered charge of vanadium pentoxide, ruthenium and 
excess aluminum in appropriate proportions to yield the desired final 
master alloy composition; (b) igniting the powdered charge in the presence 
of a molten flux, such as lime, fluorspar, or sodium chlorate, to 
aluminothermically react the vanadium pentoxide with the excess aluminum 
in the presence of ruthenium, all contained in the powdered charge, 
whereby the vanadium pentoxide is reduced to molten vanadium metal which 
alloys with molten aluminum and ruthenium and is formed into a molten 
vanadium-aluminum-ruthenium master alloy together with molten alumina 
slag; (c) gravitationally separating the molten 
vanadium-aluminum-ruthenium alloy from the alumina slag; and, (d) cooling 
said vanadium-aluminum-ruthenium alloy to a solid ingot. 
The present invention also resides in a vanadium-aluminum-ruthenium master 
alloy produced by the aforementioned aluminothermic reduction reaction in 
which the master alloy contains from about 49 to 85% by weight of 
vanadium, from about 14 to 50% by weight of aluminum, and from about 1 to 
10% by weight of ruthenium, preferably from about 59 to 70% by weight of 
vanadium, from about 29 to 40% of aluminum, and from about 1 to 10% 
ruthenium.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION 
The present invention is directed to a method for preparing 
vanadium-aluminum master alloys containing refractory metals, such as 
ruthenium, which are substantially homogeneous and free of refractory 
inclusions, and which are suitable for producing titanium base alloys 
containing refractory metals of high quality. The present invention is 
especially useful in the production of vanadium-aluminum-ruthenium master 
alloys, such as those which contain about 65% vanadium and 35% aluminum 
and also contain small amounts of ruthenium, which are free of ruthenium 
inclusions and are used to produce titanium base alloys, such as those 
which contain 4% vanadium and 6% aluminum, as well as refractory 
ruthenium. 
According to this invention, it was discovered that the refractory 
inclusion problems could be overcome if the aluminothermic reduction of 
vanadium oxide to vanadium metal was carried out in the presence of a 
small amount of ruthenium metal as well as excess aluminum. While it is 
believed that the ruthenium does not play any substantial part in the 
reduction reaction, the latent heat of the reaction provides enough energy 
to homogeneously alloy the ruthenium with the vanadium-aluminum thermite 
so as to avoid ruthenium inclusions. Titanium base alloys produced from 
such master alloys also were found to be free of ruthenium inclusions. 
The invention is described in greater detail hereinafter with reference to 
preparing exemplary nominally 65% vanadium and 35% aluminum master alloys 
containing small amounts of ruthenium. However, the invention is not 
limited to any particular master alloy composition and can include, 
without limitation, vanadium, aluminum, and refractory metals such as 
ruthenium, present in the ranges stated herein. 
In practicing the method of the invention, vanadium oxide, in powdered 
form, such as vanadium pentoxide, ruthenium, in powdered form, such as 
pure ruthenium metal, and aluminum, in powdered form, such as aluminum 
fines, are intimately mixed so that the aluminothermic reaction will occur 
rapidly and uniformly throughout the charge once it is ignited. More 
aluminum is added than is necessary to react with the vanadium oxide in 
order to produce an alloy of the metals vanadium, aluminum and ruthenium. 
The aluminothermic reduction reaction using vanadium pentoxide as the 
metal oxide and aluminum as the reducing agent can be written according to 
Equation 1. 
EQU 10 Al+3V.sub.2 O.sub.5 .revreaction.6V+5Al.sub.2.sub.O.sub.3(1) 
The mixed powdered master alloy charge is ignited in a reaction vessel for 
propagation of the reaction according to Equation 1. Various types of 
reaction vessel can be employed. For example, a copper pot or crucible may 
be used. Since the reduction reaction is exothermic, a reaction vessel 
with a water jacket to control the temperature is preferred. Furthermore, 
inasmuch as the reduction reaction produces two separate layers, i.e., an 
alloy layer covered by a molten layer of slag-containing flux, a reaction 
vessel having a tap hole toward the bottom may be employed to aid in the 
separation of alloy from the slag. If desired, the reaction vessel can 
also be constructed as to permit carrying out of the aluminothermic 
reduction reaction in an atmosphere of inert gas, such as argon. Yet, it 
is most preferred to carry out the aluminothermic reduction reaction in an 
open air atmosphere at atmospheric pressure. A preferred type of reaction 
vessel used for the practice of the invention is a water-cooled, copper, 
below-ground reaction vessel, described in U.S. Pat. No. 4,104,059 
(Perfect), which disclosure is incorporated by reference herein in its 
entirety. 
The reaction mixture can be ignited by heating the charge above the melting 
point of the aluminum, for example using an electric arc, gas burner, or 
hot metal bar. Once ignited, the reduction reaction reaches temperatures 
in excess of about 2,400.degree. C. which are sufficient to propagate heat 
through the charge to dissolve and homogenize the components of the 
resultant master alloy. After the thermite master alloy is prepared, it is 
cooled to form an ingot, and if desired can be size reduced into pieces by 
crushers, mills, of grinders to form a powdered master alloy for further 
alloying into a titanium base alloy. 
To be successful, substantially all of the reaction products resulting from 
the ignition of the charge must be melted and remain in the molten state 
long enough to perm separation of the alloy from the slag, i.e., alumina. 
The alloy and the slag separate due to the different specific gravities of 
the materials, and it is necessary for the molten materials to have 
substantial fluidity to segregate. Fluidity of the alumina slag can be 
enhanced by inclusion in the master alloy charge of certain inorganic 
materials which act as a flux to lower the viscosity of the slag and 
assist in slag formation. Typical of these materials include lime, 
fluorspar, or sodium chlorate or the like, which form a molten flux at 
reaction temperatures for absorption of the alumina slag. These materials 
generally remain unaffected by the reduction reaction. Preferably, the 
amount of flux employed generally ranges from 0.5 to 2 times the weight of 
the alumina slag formed in the process. 
The vanadium oxide used in the reduction reaction may be derived from 
either chemically pure vanadium pentoxide or less pure commercial grade 
vanadium pentoxide. An advantageous aspect of the invention is its 
effectiveness in producing master alloys from the less pure grades of 
vanadium pentoxide. The refractory ruthenium metal present during the 
reduction reaction should be substantially pure ruthenium. If desired, 
other refractory metals may be employed in the master alloy, for example, 
cobalt, rhodium, palladium, platinum, etc. For aluminum, it is preferred 
to use the highest purity aluminum commercially available. Chopped 
aluminum wire containing low impurities can be employed. However, virgin 
aluminum powder or fines is the most preferred reducing agent employed. If 
desired, other reducing agents may be employed which have a greater 
affinity for oxygen than the vanadium metal of the vanadium oxide, for 
example, silicon, calcium, or magnesium. However, aluminum is most 
preferred since it is present in the master alloy composition and has a 
high heat of formation which increases the amount of heat released by the 
reduction reaction used for producing a molten mass of the reaction 
products. 
The metal oxide, refractory metal and aluminum components may naturally 
vary in purity, and the proportions needed to provide a master alloy of a 
given composition will vary accordingly. For this reason, the respective 
amounts of materials used are expresses in terms of the compositions of 
the desired alloy. The amount of components should be so proportioned as 
to provide master alloys containing from about 49 to 85% of vanadium from 
about 14 to 50% of aluminum, and from about 1 to 10% ruthenium. Preferably 
the proportions of the components are such as to provide master alloys 
containing from about 59 to 70% of vanadium, from about 29 to 40% of 
aluminum, and from about 1 to 10% ruthenium. Unless otherwise specified, 
all percentages set forth herein refer to weight percent. 
In accordance with the practice of this invention, the 
vanadium-aluminum-ruthenium master alloys produced will be substantially 
homogeneous and relatively free of ruthenium inclusions in the ingot. The 
master alloy produced also will be relatively free of slag voids and gross 
nitride inclusions. 
The method of the invention is particularly useful in producing 65% 
vanadium and 35% aluminum master alloys containing small amounts of 
ruthenium, preferably 1 to 10% ruthenium. Such master alloys can be used 
to make various titanium base alloys, including the 4% vanadium and 6% 
aluminum alloy containing small amounts of ruthenium, preferably about 0.1 
to 1.0% ruthenium, the balance being titanium. 
In making the titanium base alloys using the master alloys of the 
invention, titanium or titanium sponge in appropriate proportions for the 
desired final alloy can be intimately mixed with powdered master alloy, 
and then the mixed charge can be formed into a consumable electrode and 
melted by a vacuum consumable-electrode arc melting, process to form the 
final titanium base alloy. 
The invention will further be clarified by a consideration of the following 
non-limiting specific example, which is intended to be purely exemplary of 
the practice of the invention used to produce vanadium-aluminum-ruthenium. 
EXAMPLE 1 
A vanadium-aluminum-ruthenium master alloy containing about 62.5% by weight 
of vanadium, about 35.5% by weight of aluminum, and about 1.5% by weight 
ruthenium the balance being minor impurities, was prepared by the 
following process: 
About 60 pounds vanadium pentoxide (V.sub.2 O.sub.5) was intimately mixed 
together with about 53 pounds aluminum fines (Al) in excess, and about 1 
pound ruthenium (Ru), an flux of about 3 pounds sodium chlorate 
(NaClO.sub.3), about 7 pounds lime (CaO), and about 5 pounds fluorspar 
(CaF.sub.2), to form a powdered charge. The powdered charge was the packed 
into a below ground, water-cooled, copper furnace and ignited with a 
sparkler to initiate the aluminothermic reduction reaction which ran in 
open air until completion. In this Example, the reaction mixture reached 
temperatures in excess of 2,400.degree. C. and proceeded for about 30 
seconds by which time substantially complete alloying had occurred. Upon 
completion of the reaction, the alloyed charge was cooled and removed from 
the reaction vessel, and then crushed into pieces, one of which was 
submitted for elemental analysis. The RAI compositional analysis is 
provided in Table 1. 
TABLE 1 
______________________________________ 
RAI Analysis 
Element 
Weight % 
______________________________________ 
V 62.51 
Al 35.46 
Ru 1.44 
B 0.0004 
C 0.032 
Fe 0.229 
Mg 0.0002 
Mo 0.020 
P 0.012 
Si 0.225 
S 0.003 
N 0.025 
O 0.087 
______________________________________ 
FIG. 1 is an SEM micrograph showing the microstructure of the V-Al-Ru 
master alloy produced in EXAMPLE 1. FIG. 2 is an EDS spectrograph showing 
the elemental map of the major components of the V-Al-Ru master alloy 
produced in EXAMPLE 1. The master alloy appeared to be uniformly alloyed, 
possibly comprising a two-phase microstructure, and contained no free 
ruthenium. 
The U.S. patents mentioned in this specification are all incorporated by 
reference herein in their entireties. 
The invention having been disclosed in connection with the foregoing 
embodiments and examples, additional variations will now be apparent to 
persons skilled in the art. The invention is not intended to be limited to 
the embodiments specifically mentioned, and accordingly reference should 
be made to the appended claims rather than the foregoing discussion of 
preferred embodiments, to assess the spirit and scope of the invention in 
which exclusive rights are claimed.