Research focuses on improving alloys.

Again this year, research on copper alloys continued to focus on ways to improve the mechanical and chemical properties of these metals.

A paper by F. Fasoyinu, University of Quebec at Chicoutimi, and M. Sahoo, C. Bibby and J. Dion, Metals Technology Laboratories (MTL) at CANMET, dealt with the microstructure and mechanical properties of copper alloys cast in the ISO permanent test bar mold.

Overall, research showed that the silicon brasses (C87500 and C87800) exhibited excellent castability in both permanent and green sand molds. The low-lead tin bronze (alloy C83450) was the most difficult to cast in a permanent mold because of its high drossing tendency and proneness to hot tearing.

The low-zinc yellow brass (C85200) also was susceptible to drossing and hot tearing, while the high-zinc yellow brass (C85800) was prone to drossing but not to hot tearing. The silicon bronzes displayed no problems in casting.

In comparing mechanical properties, the silicon brasses (C87500 and C87800) exhibited the highest tensile properties, followed by the silicon bronzes (C87600 and C97610) and the high-zinc yellow brasses (C85800).

MTL also participated in other research in copper alloys. One of the projects, which was sponsored by AFS, focused on the thermal shock resistance for permanent mold casting of copper-base alloys. The researchers--MTL's M. Sahoo, J. Dion, D. Cousineau, C. Bibby and K. Davis--found a wide range of thermal shock resistance in the samples tested.

Three types of nickel aluminides performed well in resisting cracking compared with other samples, such as nickel beryllium, stainless steel, Cu-Cr-Zr alloy and QRO 90 steel. In the group of nickel aluminides, however, the IC221 type containing chromium was found to be superior in resisting cracking, followed by the electroslag cast IC50 and the permanent mold cast IC50.

The corrosion behavior of silicon brasses (C87500 and C87800), high-zinc yellow brass (C85800), low-zinc yellow brass (C85200), leaded-tin bronze (C83450) and silicon bronzes (C87600 and C87610) in permanent mold and sand-cast conditions was studied in soft water by M. Elboujdaini, M. Sahoo, J. Dion, V. Sastri and R. Revie, all of MTL.

They found that alloys cast in permanent mold showed greater corrosion resistance than the sand-cast ones. In both permanent mold and sand-cast conditions, silicon bronze and silicon brass alloys demonstrated the best corrosion resistance, while leaded-tin bronze showed the least.

In their research on the C883600 copper alloy, Q. Liu and R. Smith, Queen's University, and M. Sahoo, MTL, concluded that filtering, degassing and the addition of Mischmetal (alone or in combination) improve the metal's hot tearing resistance.

P. Rohatgi, D. Nath and S. Ray, University of Wisconsin-Milwaukee, reviewed their research on the casting characteristics of machinable lead-free copper-graphite alloys. Their tests measured the fluidity and solidification characteristics of these alloys, and showed which ones can be successfully cast with uniform distribution of graphite particles.