Composite metals and method of making

Details Composite metals and method of making Composite metals and method of making

2001-03-16

2003-07-15

Zimmerman, John J. (Department: 1775)

Stock material or miscellaneous articles

All metal or with adjacent metals

Composite; i.e., plural, adjacent, spatially distinct metal...

C428S676000, C428S679000, C428S685000, C439S886000, C439S887000

Reexamination Certificate

active

06593010

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to composite metal materials. More particularly, the present invention relates to composite metal materials having high electrical conductivity, controlled thermal properties and excellent mechanical properties at high temperatures.
BACKGROUND OF THE INVENTION
Various applications require metals having high electrical conductivity and high strength at elevated temperatures. Such properties are typically not available from a single metal.
Generally, it is difficult to significantly modify the physical properties of alloy metals by adjusting the proportions of the alloy constituents. Composite metal materials, such as composite metal laminates, have been used to provide unique combinations of properties that can be obtained by cladding dissimilar core and clad materials. The resultant materials provide the ability to vary the electrical, mechanical and thermal properties.
Electrically conductive spring materials and members used in making electrically conductive spring contacts in switches and in sockets for mounting integrated circuits on printed circuit boards are examples of applications requiring high electrical conductivity and high strength at elevated temperatures. Other applications for materials having high electrical conductivity and high strength are lead frames for semiconductors. In many applications, electrical connectors are used in extremely high temperature environments. For example, automobile engine compartments include electrical connectors that are exposed to extreme high and low temperatures. Therefore, it is desirable to provide an electrical connector that exhibits improved resistance to stress relaxation at high temperatures.
A variety of materials are used to manufacture electrically conductive springs and connectors. Examples of such material include beryllium copper and copper clad stainless steels. Beryllium copper alloys are used in many applications requiring electrical conductivity and mechanical reliability at high temperatures.
Due to potential concerns about adverse health and environmental effects associated with beryllium and beryllium copper use, it would be desirable to provide a material that did not contain beryllium but still had the desirable electrical and mechanical properties of beryllium copper alloys. However, research has yielded few materials that exhibit the combined properties of electrical conductivity and mechanical reliability over a wide temperature range. Therefore, it would also be desirable to provide a composite material having electrical, thermal and mechanical properties that could be tuned or adjusted over a wide temperature range. It would be particularly advantageous if the properties could be tuned or adjusted by varying the relative proportions of the materials in the composite material and/or by heat treating the material to provide a material that has high mechanical strength and capable of being manipulated into complex shapes.
SUMMARY OF INVENTION
Accordingly, the present invention generally provides a composite material including a core of precipitation hardenable core and a clad including a transition metal or transition metal alloy. As used herein, the term core is not limited to mean that the core is completely surrounded by cladding material. Instead, the term core is used in a broader sense to mean the innermost part of the composite material, and at least one surface of the core is covered by cladding material. For example, in a situation in which a planar composite material is provided, at least two major surfaces of the plane would be covered with cladding material.
Preferably, the precipitation hardenable core material has a coefficient of thermal expansion (CTE) less than about 9 parts per million per ° C. (ppm/° C.) over the temperature range of 20° C. to 100° C. According to one aspect of the invention, the core metal includes 32 to 50 percent by weight of Ni, 1.5 to 3.5 percent by weight of Ti, and 0.05 to 1.0 percent by weight of Al. According to this aspect, the balance of the material includes Fe. Preferably, the core metal includes 35 to 45 percent by weight of Ni, 2 to 3 percent by weight of Ti, and the balance Fe. The core material may also include trace impurities including, but not limited to Mn, Si, C, S, and P. Preferably, each of the trace impurities is present in amount less than one weight percent.
According to another aspect of the invention, the cladding layer metal has a coefficient of thermal expansion greater than 9 ppm/° C. in the temperature range of 20° C. to 100° C. The cladding material preferably includes a metal selected from the group consisting of copper, nickel, zinc and alloys thereof.
In another aspect of the invention, the core material comprises 50% to 90% by volume of the composite material. Preferably, the core material comprises 70% to 90% by volume of the composite material. The coefficient of thermal expansion of the composite is preferably less than about 9 ppm/° C. in the temperature range of 20° C. to 100° C. In addition, according to another aspect, the ratio of the 0.2% offset yield strength to tensile strength of the composite after heat treatment at 750° C. from the annealed condition is less than 0.85.
Another aspect of the invention relates to a method of making a composite material including providing a core of the precipitation hardenable metal described above and at least one layer of a transition metal or transition metal alloy cladding covering at least one surface of the core and roll bonding the core layer and the cladding layer together to form the composite material. Another aspect of the method may further include of annealing the composite material at a temperature between 850° C. and 1000° C. According to another aspect, the invention may include heat treating the composite material at a temperature of 700° C. to 800° C. for at least one-half hour. In a preferred aspect of the invention, the heat treatment is performed so that a gamma phase material is formed during said heat treatment. Preferably, the heat treatment is performed so that the ratio of the 0.2% offset yield strength to tensile strength of the composite after heat treatment from the annealed condition is less than 0.85.
In another aspect, the roll bonding step is performed in a single pass with a thickness reduction of at least 30% and the clad layers comprise at least 20% of the composite by volume. According to this aspect, the core and clad materials are planar, and an equivalent volume of clad material covers both major surfaces of the core.
One advantage of the present invention is that the composite material and the method of making the composite material provide a material that has adjustable or tunable electrical, thermal and mechanical properties. The precipitation hardenable core enables the strength properties of the composite material to be adjusted by heat treating the material. The electrical and thermal properties of the composite material can be adjusted by varying the ratio of the cladding material to the core material.
Additional features and advantages of the invention will be set forth in the description which follows. It is to be understood that both the foregoing general description and the following detailed description are exemplary and are intended to provide further explanation of the invention as claimed.
DETAILED DESCRIPTION
The present invention relates to the discovery of a unique combination of materials to provide a composite having tunable electrical, thermal and mechanical properties. Advantageously, the properties of the material can be tuned by adjusting the volume ratio of the core and cladding materials that form the composite. Alternatively, the properties of the composite can be adjusted by heat treating the material. Of course, the properties of the composite can be optimized by adjusting the relative amounts of the core and cladding materials and by heat treating the composite.
The core material includes a precipitation hardenable material having a coefficient of thermal expansion

Affiliated with

Also associated with

Rating

Composite metals and method of making does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Composite metals and method of making, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Composite metals and method of making will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3052211