CO-SINTERED MULTI-SYSTEM TUNGSTEN ALLOY COMPOSITE
A composite is produced by the steps of (a) blending a first mixture of metallic powders; (b) compacting the blended first mixture of metallic powders to a plurality of discretely shaped articles; (c) blending a second mixture of metallic powders; (d) mixing the plurality of discretely shaped articles with the blended second mixture of metallic powders to form a precursor blend; (e) compacting the precursor blend; and (f) sintering the precursor blend. The composite has a metallic matrix with embedded shapes dispersed throughout the matrix where the embedded shapes have an incipient liquid phase sintering temperature less than an incipient liquid phase sintering temperature of the matrix.
1 . A method for the manufacture of a composite metal component, comprising the steps of:
a) blending a first mixture of metallic powders;
b) compacting said blended first mixture of metallic powders to a plurality of discretely shaped articles;
c) blending a second mixture of metallic powders;
d) mixing said plurality of discretely shaped articles with said blended second mixture of metallic powders to form a precursor blend;
e) compacting said precursor blend; and
f) sintering said precursor blend.
2 . The method of claim 1 wherein said sintering is at a temperature effective to liquid phase sinter said discretely shaped articles and solid state sinter said second mixture of powders.
3 . The method of claim 2 wherein both said first mixture of powders and said second mixture of powders are tungsten-base.
4 . The method of claim 3 wherein said sintering temperature is between 1200° C. and 1350° C.
5 . The method of claim 4 wherein said sintering temperature is between 1225° C. and 1275° C.
6 . The method of claim 4 wherein said first mixture of powders is selected to further contain copper and said second mixture of powders is selected to further contain at least one of iron, nickel and cobalt.
7 . The method of claim 6 including the additional step of machining said sintered precursor blend to a finished component.
8 . The method of claim 7 wherein said machining step forms a nosecone for a fragmenting warhead.
9 . A method comprising:
forming a first mixture of a first set of metallic powder constituents, the first mixture having a first incipient liquid phase sintering temperature;
forming a second mixture of a second set of metallic powder constituents, the second mixture having a second incipient liquid phase sintering temperature and an incipient solid phase sintering temperature,
wherein the first incipient liquid phase sintering temperature is less than the second incipient liquid phase sintering temperature and greater than the incipient solid phase sintering temperature;
compacting the first mixture into a plurality of compacted shapes;
forming a combination including a suspension of the compacted shapes in the second mixture;
compacting the combination; and
sintering the compacted combination.
10 . A method according to claim 9 , wherein the first mixture includes at least 50% by weight of tungsten, molybdenum or a mixture thereof.
11 . A method according to claim 10 , wherein the first mixture further includes a constituent effective to depress the melting point of said first mixture.
12 . A method according to claim 11 , wherein said constituent includes copper, cobalt, manganese or a combination thereof.
13 . A method according to claim 9 , wherein the second mixture includes at least 50% by weight of tungsten, molybdenum or a mixture thereof.
14 . A method according to claim 9 , wherein the second mixture is a tungsten heavy alloy matrix including 10% to 100% by weight of tungsten, with the balance including nickel, iron, cobalt and/or copper.
15 . A method according to claim 9 , wherein the first incipient liquid phase sintering temperature is at least 10° C. less than the second incipient liquid phase sintering temperature.
16 . A method according to claim 15 , wherein the first incipient liquid phase sintering temperature is from 20° C. to 50° C. less than the second incipient liquid phase sintering temperature.
17 . A method comprising:
mixing a first plurality of metallic powders to form a first mixture having a first incipient liquid phase sintering temperature;
mixing a second plurality of metallic powders to form a second mixture having a second incipient liquid phase sintering temperature and an incipient solid phase sintering temperature;
compacting the first mixture into shapes of a desired configuration;
forming a metallic matrix including the second mixture with a plurality of said shapes embedded therein; and
sintering the matrix so that the matrix has a microstructure commensurate with solid state sintering and the embedded shapes have a microstructure commensurate with liquid state sintering.
18 . A method according to claim 17 , wherein the sintering is performed at a temperature above the first incipient liquid phase sintering temperature, below the second incipient liquid phase sintering temperature, and above the incipient solid phase sintering temperature.
19 . A method according to claim 17 , wherein the first incipient liquid phase sintering temperature is from 20° C. to 50° C. less than the second incipient liquid phase sintering temperature.
20 . A method according to claim 17 , wherein the sintering is performed so that an intermetallic rich diffusion layer bonds the matrix and the embedded shapes.