Effects of a Small Amount of Added Elements on the Ductility of a Cu-8 mass%Sn Alloy at Elevated Temperatures

Abstract

In connection with hot shortness of tin bronzes, the ductility of a Cu-8 mass%Sn binary alloy and of the alloys singly containing B, Mg or P of about 0.1 mol% was investigated in detail at elevated temperatures up to 1073 K. All the alloys showed markedly poor ductility at temperatures from 673 to 873 K accompanied by intergranular fracture on account of so-called intermediate temperature embrittlement. The ductility was improved to a greater extent at higher temperatures in B-bearing and Mg-bearing alloys, but to a lesser extent, in the binary and P-bearing alloys. The marked improvement in ductility which was accompanied by transgranular fracture was commonly observed regardless of strain rate and grain size in the B-bearing alloy. This alloy showed excellent ductility together with fine recrystallized structures which was caused by dynamic recrystallization at higher temperatures. Recrystallization temperatures, however, were substantially the same in four sorts of alloys. In the binary and P-bearing alloys, intergranular fracture at higher temperatures was shown to start from the specimen surface. This fact suggested that the strength of the grain boundary of these alloys was reduced especially near the surface. Based on the result of oxidation experiment, the decrease in the grain boundary strength was surmised to be inhibited in B-and Mg-bearing alloys by the suppression of oxygen penetration through the grain boundary.

Improvement in Hot Ductility in a Cu-4.4 mol%Sn Alloy by Adding a Small Amount of Third Elements

“…In connection with grain boundary cracking, several experiments, including the observation of crack propagation along grain boundaries during hot deformation and the observation of slip band structures were carried out. In the course of these experiments, almost the same results were obtained as those reported previously in B-and Mg-bearing alloys (2). In addition, it was shown that internal oxidation of the alloy or preferential oxidation of grain boundaries was significantly suppressed by Y(Ce) addition in the same way as the addition of B.…”

“…2. In this figure, the Ca-bearing alloy as well as the binary alloy exhibits severe grain boundary cracking, while such grain boundary cracking almost disappears in the Y-and Ce-bearing alloys in the same way as in the B-bearing alloy (2) . In connection with grain boundary cracking, several experiments, including the observation of crack propagation along grain boundaries during hot deformation and the observation of slip band structures were carried out.…”

“…Ingots of the alloys were homogenized at 973 K for 18ks in a reducing atmosphere of dissociated ammonia gas. The procedures for fabricating round tensile specimens were the same as reported elsewhere (2), and the specimens were made with a gauge length of 10 mm and a diameter of 4 mm. The mean grain size of specimens controlled by vacuum anTensile tests were conducted at temperatures ranging from 573 to 1073 K in a vacuum (1 Pa) by use of an Instron type testing machine.…”

Intermediate temperature embrittlement of copper alloys

“…As for pure copper 6,9,90,[125][126][127][128][129] and except for very rapid (impact) deformation, as the strain rate increases the trough narrows and becomes more shallow for brasses 68,125,126,128,137,143,150,[170][171][172][173] , bronzes 174,175 , cupro-nickel alloys 9, 176-178 and dispersion hardened copper 6,153,160,179,180 . For two (70-30 and 80-20) a-brasses, T E was found to be strain-rate dependent, but not T R 171 .…”

Mechanical Properties of Biomedical Co-33Cr-5Mo-0.3N Alloy at Elevated Temperatures

“…It has been reported that the causes for ''Intermediate temperature embrittlement'' are the segregation of solute atoms and impurities to the grain boundaries or etc. [13][14][15] Meanwhile, as noted above, the elongation of Hi Cr-& Hi N-Co-Cr-Mo alloy increases at intermediate temperatures depending on strain rates. As stated in Fig.…”