Experimental Investigation and Thermodynamic Modeling of Influence of Nickel and Titanium Content on the Structure and Selected Properties of Tin Bronzes.

Janusz Kozana,Marcin Piękoś,Aldona Garbacz-Klempka,Małgorzata Perek-Nowak,Paweł Pałka

doi:10.3390/ma14205944

Abstract

Investigations are conducted in order to maintain or to improve the selected properties of the group of foundry copper-tin alloys with nickel and titanium additions, at a limited fraction of the critical (deficit) element such as tin. The crystallisation process, as well as changes of the microstructure and selected mechanical properties of the CuSn8 alloy—occurring due to introducing alloying additions—were analysed. Investigations of the macro and microstructure were performed using optical and scanning electron microscopy. Based on the thermal analysis and thermodynamic modelling using the CALPHAD (CALculations of PHAse Diagrams) method, the crystallisation process was analysed. The identification of phases was performed by XRD (X-ray diffraction). In addition, such parameters as tensile strength-UTS, elongation-A and hardness-HBS were tested. Under the influence of the introduced titanium, the columnar crystals are reduced due to the crystallisation of the alloy at the walls of the mould. Precipitations (intermetallic phases) crystallize first (primary). The intermetallic phases associated with the presence of the alloying elements nickel and titanium are located in the interdendritic regions. In tin bronzes with titanium additions, hardness (HBS) increases, tensile strength (UTS) negligibly decreases, while elongation (A) significantly decreases. In the case of CuSnNi bronze, the addition of 0.2 wt.% Ti increases the hardness and increases ultimate tensile strength (UTS), while reducing the elongation (A). Higher Ti additions increase HBS, slightly decrease the tensile strength, and significantly reduce the elongation.

Highlights

Copper alloys are the most known and researched alloys [1,2]
The group of Cu-Sn alloys selected for tests as well as the obtained results caused by nickel and titanium additions indicated several interesting changes within crystallisation, optical and scanning metallography and identifications of precipitates and phases, which were tested by means of the scanning microscopy SEM-EDS and X-ray diffraction tests (XRD)
The performed investigations concerning influences of nickel and titanium additions to CuSn8 tin bronze allowed for observing several changes within the crystallisation, macro- and microstructures, SEM-EDS, XRD results and selected mechanical properties

Summary

Introduction

Known and applied already in the antiquity, still constitute the important and irreplaceable group of alloys used for production of machines and parts of devices [3–9]. Due to higher requirements to modern materials, high prices of tin and its short supply, the substitutes of this group of elements are looked for and applied [19–22]. This is realised by the development of new alloys based on alloying additions, such as: zinc, lead, phosphor, nickel, iron, titanium and aluminium, as well as on refining, modification and the way of casting (gravity, centrifugal, sand or metal moulds) [23–29]

Methods

Results

Discussion

Conclusion