Process for the electrodeposition of low stress nickel-manganese alloys
A process for electrodepositing a low stress nickel-manganese multilayer alloy on an electrically conductive substrate is provided. The process includes the steps of immersing the substrate in an electrodeposition solution containing a nickel salt and a manganese salt and repeatedly passing an electric current through an immersed surface of the substrate. The electric current is alternately pulsed for predetermined durations between a first electrical current that is effective to electrodeposit nickel and a second electrical current that is effective to electrodeposit nickel and manganese. A multilayered alloy having adjacent layers of nickel and a nickel-manganese alloy on the immersed surface of the substrate is thereby produced. The resulting multilayered alloy exhibits low internal stress, high strength and ductility, and high strength retention upon exposure to heat.
1. A process for electroplating a layered nickel and nickel-manganese alloy onto a metal substrate comprising:
(a) providing an electrolyte solution containing a nickel salt and a manganese salt;
(b) providing a conductive substrate suitable for nickel and manganese electrodeposition;
(c) immersing at least a portion of the substrate in the electrolyte solution; and
(d) passing an electric current through the immersed surface of the substrate, the electric current being alternately pulsed for predetermined durations between a first electrical current that is effective to electrodeposit nickel and a second electrical current that is effective to electrodeposit nickel and manganese, thereby producing a multilayered alloy having adjacent layers of nickel and a nickel-manganese alloy on the immersed surface of the substrate,
wherein the concentration of manganese in the electrolyte solution is lower than the concentration of nickel.
2. The process of claim 1 wherein the concentration of manganese in the electrolyte solution ranges from approximately 0.1 g/L to approximately 5 g/L.
3. The process of claim 1 , wherein step (d) is conducted at a temperature ranging from approximately 20° C. to approximately 35° C.
4. The process of claim 1 , wherein the first electrical current ranges from approximately 1 mA/cm 2 to approximately 6 mA/cm 2 .
5. The process of claim 1 , wherein the second electrical current ranges from approximately 12 mA/cm 2 to approximately 25 mA/cm 2 .
6. The process of claim 4 , wherein the second electrical current ranges from approximately 12 mA/cm 2 to approximately 25 mA/cm 2 .
7. The process of claim 4 , wherein the first electrical current is applied to the substrate in pulses ranging from approximately 0.01 second to approximately 10 seconds.
8. The process of claim 5 , wherein the second electrical current is applied to the substrate in pulses ranging from approximately 0.01 second to approximately 10 seconds.
9. A multilayered alloy comprising a plurality of alternating layers of nickel and a nickel-manganese alloy.
10. The multilayered alloy of claim 9 , wherein each of the alternating layers is of the same thickness.
11. The multilayered alloy of claim 9 , wherein each of the alternating layers is of a different thickness.
12. The multilayered alloy of claim 9 , wherein each of the alternating layers of nickel and nickel-manganese alloy has a thickness of from approximately 3 Å to approximately 20 nm.
13. The multilayered alloy of claim 12 , wherein each of the alternating layers of nickel and nickel-manganese alloy has a thickness of from approximately 2 nm to approximately 5 nm.
14. The multilayered alloy of claim 9 , wherein the multilayered alloy has as-plated strength of greater than approximately 900 MPa.
15. The multilayered alloy of claim 9 , wherein the multilayered alloy exhibits internal stress of less than approximately 100 MPa.
16. The multilayered alloy of claim 9 , wherein the multilayered alloy exhibits greater than approximately 6% total ductility.
17. The multilayered alloy of claim 14 , wherein the multilayered alloy retains at least 85% of as-plated strength after heating at 600° C. for 1 hour.
18. The multilayered alloy of claim 9 , wherein the multilayered alloy exhibits a variation in compositional uniformity of less than approximately 15%.
19. A micropart fabricated using the method of claim 1 .
20. The micropart of claim 19 , wherein the combined height of the adjacent layers of nickel and a nickel-manganese alloy ranges from approximately 200 μm to approximately 2 mm.
21. The micropart of claim 19 , wherein the micropart comprises features having an aspect ratio of greater than approximately 10.