Annealing behavior of Cu-7at.%Pd alloy deformed by cold rolling
Introduction
The copper-palladium system belongs to binary systems which have an affinity for ordering [1]. According to the phase diagram, copper and palladium form a continuous series of fcc solid solution at higher temperatures. Under critical temperatures, depending on composition, some superlattices are formed [2]. Long range ordering of Cu3Pd (α′) superlattice with a fcc structure of the L12 (Cu3Au) type typically occurs in the concentration range of ∼12 wt.% Pd to 32 wt.% Pd [3,4]. One dimensional anti-phase domain (APD) or long period superlattice (1D LPS) was confirmed in alloys with ∼26 wt.%Pd - 39 wt.%Pd. Two-dimensional APD (or 2D LPS) occurs in alloys with ∼28 wt.%Pd – 43 wt.%Pd [4,5]. Both LPSs have ordered face-centered tetragonal structure of the ordered Cu3Au type. In alloys with ∼49 wt.%Pd to 60 wt.% Pd, ordered lattice CuPd (β) with bcc structure of the B2 (CsCl) type occurs [2,[6], [7], [8]].
The Cu-Pd alloys are used extensively in many applications such as oxidation catalysts [9], hydrogen separation membranes [10,11], functional materials [6], etc. A wide range of applications for these alloys is due to their unique properties such as good corrosion resistance and high electrical conductivity. Wider usage of these materials is limited by their lower mechanical properties. An improvement in mechanical properties can be achieved by described long-range ordering, which usually is not efficient enough [6]. However, Vitek and Warlimont [12] have shown a significant hardening in dilute Cu-Pd alloys, where long-range ordering does not occur generally. This hardening occurs only after cold deformation and annealing up to the recrystallization temperature, and it is called anneal hardening [12]. Anneal hardening effect was mostly studied in copper based alloys with aluminum [[13], [14], [15]], and it was manifested by an increase in the mechanical properties of annealed samples compared to deformed ones. It means that samples in annealed state have higher mechanical properties than in deformed state. Vitek and Warlimont [12] have confirmed the anneal hardening effect in some other binary copper based alloys with palladium, zinc, gold, gallium, nickel, and rhodium. Volkov et al. [16] obtained an increase in microhardness values of deformed Cu-8at.%Pd alloy after annealing at 200 °C and 250 °C for 15 min, but this anomaly during short time annealing was not considered in the paper but only prolonged annealing. However, other studies about the intensity and mechanism of anneal hardening effect in the Cu-Pd alloys could not be found in the literature. Therefore, in this investigation, the annealing was performed on the cold-rolled Cu-7at.%Pd samples to study the effect of thermo-mechanical treatment on the anneal hardening effect. This paper correlates the mechanical properties and electrical conductivity with microstructure during the thermo-mechanical treatment which included solution annealing, quenching, cold rolling, and annealing, and it evaluates the contribution of anneal hardening effect to the overall hardening of the cast Cu-7at.%Pd alloy.
Section snippets
Experimental procedure
Pure palladium (99.97% purity) and electrolytic copper (99.95% purity) as starting materials were melted in a high-frequency induction furnace, and then cast in a steel mold with dimensions of 10 mm × 30 mm x 100 mm. The chemical composition of the cast ingot in atomic percent was Cu-7Pd. The ingot was cut into samples with dimensions of 10 mm × 30 mm x 5 mm. These samples were solution annealed at 700 °C for 2 h followed by quenching into cold water. High purity hydrogen was used as a
Properties and microstructure after casting, quenching and cold rolling
Table 1 shows the values of hardness, microhardness and electrical conductivity of Cu-7Pd alloy after casting and different stages of thermo-mechanical treatment.
It is noted that the addition of 7 at.% of palladium in copper results in considerable reduction in electrical conductivity from 58 MSm−1 [19] to 16.18 MSm−1. The decrease in electrical conductivity of copper by the conventional alloying is associated with an increase in mechanical properties (hardness and microhardness) due to the
Conclusions
The anneal hardening behavior of Cu-7Pd alloy after deformation by cold rolling has been investigated. Based on the obtained results, the following conclusions can be drawn:
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Quenching caused a slight increase in mechanical properties and a decrease in electrical conductivity. Additional cold rolling after quenching gave rise to further improvement in both mechanical and physical properties.
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A hardening in combination with an improvement in electrical conductivity during the low-temperature
Acknowledgment
The research results were developed under the Project TR 34003 “Conquering the Production of Cu-Au, Cu-Ag, Cu-Pt, Cu-Pd, Cu-Rh Cast Alloys of Improved Properties by Applying the Anneal Hardening Mechanisms“ for which the funds were provided by the Ministry of Education, Science and Technological Development of the Republic of Serbia.
References (53)
- et al.
Stability and instability of long-period superstructures in binary Cu–Pd alloys: a first-principles study
Acta Mater.
(2009) - et al.
Thermodynamic modelling of the Cu–Pd–H system
Comput. Coupling Phase Diagrams Thermochem.
(2007) - et al.
Preparation and characterization of Pd–Cu composite membranes for hydrogen separation
Chem. Eng. J.
(2003) - et al.
Ordered bcc phases in a Cu–Pd–Mg hydrogen separation membrane alloy
J. Alloys Compd.
(2012) - et al.
The production and application of metal matrix composite materials
J. Mater. Process. Technol.
(2000) - et al.
Study of anneal hardening in cold worked Cu-Au alloy
J. Alloys Compd.
(2016) - et al.
The effect of plastic deformation on the resistivity and hall effect of copper-palladium and gold-palladium alloys
Acta Metall.
(1967) - et al.
Atomic ordering in alloys: stable states and kinetics
Mater. Sci. Eng., A
(2002) - et al.
Electrical resistivity change during continuous heating in Cu-18at.%Pd alloys quenched from various temperatures
Scripta Mater.
(1998) - et al.
Microstructure evolution and properties of Cu-Ag microcomposites with different Ag content
Mater. Sci. Eng.
(2006)
Effect of cold plastic deformation on electrical conductivity of various materials
Mater. Des.
High-conductivity binary Mg-Zn sheet processed by cold rolling and subsequent aging
J. Alloys Compd.
Order-disorder and cold-work phenomena in Cu-Pd alloys
Acta Metall.
A new annealing hardening mechanism in pre-twinned Mg–3Al–1Zn alloy
Mater. Sci. Eng., A
Anomalous hardening in copper due to the growth of deformation-induced micro-twins after annealing
Scripta Mater.
Strengthening mechanisms in nanostructured high-purity aluminium deformed to high strain and annealed
Acta Mater.
Order strengthening in α-Cu-Al Alloys as influenced by grain size and solute content
Mater. Sci. Eng.
Anneal hardening in cold rolled PM Cu-Au alloy
Mater. Sci. Eng., A
Unusual hardening behaviour in heavily cryo-rolled Cu-Al-Zn alloys during annealing treatment
Mater. Sci. Eng., A
Effect of solute segregation on the strength of nanocrystalline alloys: inverse Hall–Petch relation
Acta Mater.
Evolution of defect structures during cold rolling of ultrafine-grained Cu and Cu–Zn alloys: influence of stacking fault energy
Mater. Sci. Eng.
Determining the minimum grain size in severe plastic deformation process via first-principles calculations
Acta Mater.
Effect of thermo-mechanical treatment on properties improvement and microstructure changes in copper–gold alloy
Mater. Des.
Properties improvement and microstructure changes during thermomechanical treatment in sintered Cu-Au alloy
Trans. Nonferrous Metals Soc. China
The recovery and recrystallization of cold rolled V-W-Ti alloys
J. Nucl. Mater.
Effect of forming conditions on the softening behavior in coarse grained structures
Mater. Sci. Eng., A
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