DFT® composites were developed to combine the desired physical and mechanical attributes of two or more materials into a single wire or ribbon system. As a result of extreme compressive forces imparted during the processing of the dissimilar materials, the mechanical bond formed between surfaces has been found to be metallurgically sound. This feature has given rise to a number of novel applications of DFT® wire, cable or ribbon.
One of the more common uses of DFT® wire is found in the medical device industry where designers have integrated the strength and biocompatibility of implant grade alloys with desired properties of other materials. The composite typically uses the outer sheath to impart strength while the core material is designed to provide conductivity, radiopacity, resiliency or MRI enhancement.
DFT® wire enables the unique ability to match dissimilar materials to provide a variety of properties in a single wire system. This technology can be utilized by the engineer to resolve technical issues cost effectively.
Fort Wayne Metals has the capability to create these DFT® wire materials in sizes from 3.175 mm to 0.017 mm [0.125 in to 0.0007 in] or smaller depending on the constituents.
A typical 35N LT®/Silver DFT®wire material (MP-DFT-Ag) may have a variety of tensile values depending upon the amount of cold work and core percentages of the individual wires. In addition, the table in Fig. 2 is presented to compare the electrical resistivity of various core percentages to that of solid 35N LT® wire, a common pacemaker lead material. 35N LT®, 316LVM and Conichrome® tubing is kept in stock for the outer sheath. Core options, in wire form, are more abundant in general inventory.
Since DFT® composites are highly customizable, exact mechanical properties vary based on construction, primarily influenced by coldwork percentages and fill ratio. You can use the chart below to compare properties for 35N LT® alloy DFT® composites with a variety of coldwork percentages and silver fill ratios.
| % CW | 25% Ag | 28% Ag | 33% Ag | 41% Ag |
|---|---|---|---|---|
| 0% | 158,200 | 148,800 | 149,600 | 124,100 |
| 20% | 201,300 | 191,200 | 192,600 | 162,800 |
| 37% | 225,600 | 216,500 | 213,800 | 165,800 |
| 50% | 237,300 | 227,300 | 224,700 | 192,400 |
| 61% | 246,000 | 236,000 | 232,400 | 200,000 |
| 69% | 256,700 | 244,000 | 239,300 | 206,400 |
| 75% | 261,200 | 248,100 | 242,300 | 209,500 |
| 80% | 267,800 | 254,500 | 249,300 | 214,900 |
| 84% | 276,000 | 264,000 | 261,600 | 217,000 |
| 87% | 278,200 | 264,300 | 262,300 | 225,000 |
| 90% | 277,300 | 264,300 | 258,400 | 223,300 |
| 92% | 281,900 | 266,900 | 254,700 | 232,200 |
Since DFT® composites are commonly used as conductors, you can use the table below to compare 35N LT® alloy DFT® composites with a silver core to solid 35N LT® alloy wire.
| Wire size | 25% Ag | 28% Ag | 33% Ag | 41% Ag | Solid 35N LT® alloy wire |
| 0.152 mm [0.006 in] |
3.324 ohm/m [1.013 ohm/ft] |
2.987 ohm/m [0.91 ohm/ft] |
2.555 ohm/m [0.779 ohm/ft] |
2.075 ohm/m [0.632 ohm/ft] |
56.63 ohm/m [17.26 ohm/ft] |
| 0.102 mm [0.004 in] |
7.479 ohm/m [2.280 ohm/ft] |
6.722 ohm/m [2.049 ohm/ft] |
5.748 ohm/m [1.752 ohm/ft] |
4.668 ohm/m [1.423 ohm/ft] |
127.4 ohm/m [38.84 ohm/ft] |
| 0.051 mm [0.002 in] |
29.90 ohm/m [9.113 ohm/ft] |
26.87 ohm/m [8.191 ohm/ft] |
22.99 ohm/m [7.006 ohm/ft] |
18.67 ohm/m [5.691 ohm/ft] |
509.6 ohm/m [155.3 ohm/ft] |
| 0.025 mm [0.001 in] |
119.9 ohm/m [36.53 ohm/ft] |
107.5 ohm/m [32.76 ohm/ft] |
94.36 ohm/m [28.79 ohm/ft] |
74.69 ohm/m [22.77 ohm/ft] |
2039 ohm/m [621.4 ohm/ft] |