Microstructure-mechanical property relationship to copper alloys with shape memory during thermomechanical treatments

Abstract

The phase transformations during fabrication and aging after cold deformation in three polychrystalline copper alloys of the Cu-Al-Ni system with shape memory effect (SME) were characterized. Some phase transformations were identified with clear repercussion in their mechanical properties during thermomechanical treatments. Around 430 °C, mutual effects of ␤-phase recrystallization and precipitation of ␥ 2 and NiAl phases were observed. Close to 600 °C the dissolution of phase ␣ was observed, beginning transformation into ␤ phase process. Brittle phases such as ␥ 2 and NiAl began to precipitate during a short exposure time at 380 °C, 585 °C, 600 °C, and 700 °C temperatures. The phase transformations were intensified due to the plastic deformation that acted as a driving force for the diffusion processes. The introduction of chemical elements inhibited the grain growth and increased the structural disorder generating an elevation in the hardness property.

Effect of Mn on microstructure and properties of Cu-12Al powder metallurgy alloy

“…γ-Al 4 Cu 9 is similar to cementite in carbon steel and is distributed in a network. The proportion of the γ phase increases with higher Al content, which in turn leads to increased hardness and strength but lower plasticity [8][9][10][11]. Cu-12Al close to the eutectoid component has a eutectoid microstructure with high strength and hardness, but poor plasticity and toughness [12][13][14].…”

Influences of 2.5wt% Mn addition on the microstructure and mechanical properties of Cu-Al-Ni shape memory alloys

“…Grains in the Cu-Al-Ni alloy systems grow easily and the grain size becomes large enough. Researches show that grain sizes vary from 1 to 3 mm in these alloys [16][17]. This work indicates that the grain size of the Cu-Al-Ni alloy can be controlled by the introduction of Mn element.…”

Martensitic Transformation Under Compression of a Plasma Processed Polycrystalline Shape Memory CuAlNi Alloy

“…In the case of thermally treated CuAlNi alloy investigated by Sari and Kirindi 41 , precipitation was indicated to occur during the initial annealing treatment. In particular, annealing at 650°C 63,64 caused precipitates that restricts the mobility of the martensite variants and twin interfaces. Failure with completely intergranular fracture was attributed to the presence of brittle precipitate phases at the grain boundaries 14,63 .…”