Precipitation Behavior and Properties of Cu-Ti Alloys with Added Nitrogen

Abstract

The effects of adding nitrogen (N) to age-hardenable Cu-Ti alloys on their microstructure, hardness, and conductivity have been investigated. It was found that the aging of Cu-Ti-(0.060.6) mol% N alloys resulted in the continuous formation of finely precipitated needleshaped ¡-Cu 4 Ti grains and the discontinuous formation of coarse cellular components composed of a stable ¢-Cu 4 Ti and Cu solid solution at the grain boundaries, in a manner similar to that in the case of conventional Cu-Ti alloys without any N. Furthermore, a small amount of granular TiN particles was also formed in Cu-Ti-N alloys. The hardening behavior of Cu-Ti-N alloys was similar to that of Cu-Ti alloys without N. This similarity was attributed to the finely dispersed precipitation of ¡-Cu 4 Ti that was similar between Cu-Ti alloys with and without N. The electrical conductivity of Cu-Ti-N alloys increased more steeply than that of Cu-Ti alloys without N. This is because in the case of Cu-Ti-N alloys, the coprecipitation of ¡-Cu 4 Ti, ¢-Cu 4 Ti, and TiN efficiently reduced the Ti concentration in the matrix. Thus, the conductivity of peak-hardened Cu-Ti-N alloys can be improved by optimizing the N concentration and aging temperature.

Characterization of Tribological and Mechanical Properties of the Si3N4 Coating Fabricated by Duplex Surface Treatment of Pack Siliconizing and Plasma Nitriding on AISI D2 Tool Steel

“…From an industrial point of view, pack cementation technique results simple, cost effective, and suitable for mass production for coating complex geometry substrates. [24][25][26][27] The present study focused on the production and characterization of Si 3 N 4 coating on AISI D2 tool steel through a duplex treatment via pack siliconizing followed by plasma nitriding. First, optimized siliconizing coatings at high and low temperature were obtained.…”

Analysis of β´(Cu4Ti) Precipitation During Isothermal Aging of a Cu-4wt.%Ti Alloy

“…After prolonged aging, the cellular precipitation of the stable orthorhombic β Cu 4 Ti phase takes place by nucleation and growth on grain boundaries which is the main cause for the decrease in the mechanical strength in the later stage of aging 1 . The mechanical strength of Cu-Ti alloys has been improved either by the addition of a third alloying element such as Chromium, zirconium, carbon, nitrogen or hydrogen [9][10][11] or by using cold work previously to the aging treatment 12,13 . In the former case, the precipitation sequence was similar to that observed in the binary alloy; however, the presence of a different precipitates such as titanium chromide, nitride, carbide or hydride was also reported to occur during aging [9][10][11] .…”

“…The mechanical strength of Cu-Ti alloys has been improved either by the addition of a third alloying element such as Chromium, zirconium, carbon, nitrogen or hydrogen [9][10][11] or by using cold work previously to the aging treatment 12,13 . In the former case, the precipitation sequence was similar to that observed in the binary alloy; however, the presence of a different precipitates such as titanium chromide, nitride, carbide or hydride was also reported to occur during aging [9][10][11] . In the latter case, the cold work, used after solution treatment and quenching, has been reported 12,14 to promote the precipitation of titanium on dislocations and to inhibit the precipitation of the β´ Cu 4 Ti and β Cu 4 Ti phases during aging.…”

Ti and nitride surface modification of copper by pack cementation

“…Several materials such as aluminium, chromium and titanium have been used for the formation of binary phases in order to improve the copper performance [5][6][7]. Most of them, aimed to improve the mechanical properties, oxidation resistance and tribological properties by using sophisticated and two-step techniques, with elevated cost, such as hot rolling and quenching, arc melting and quenching, melting and plasma nitriding [8][9][10]. In contrast, pack cementation is a simple, environmental friendly and economic technique which is suitable for coating normal and complex geometry substrates [11][12][13].…”