Investigation of the early stages of deformation of two phase copper-aluminum alloys
- PDF / 1,359,615 Bytes
- 7 Pages / 603.28 x 788 pts Page_size
- 101 Downloads / 265 Views
I.
INTRODUCTION
M A N Y commercial aluminum bronzes (Cu-AI alloys), known for their high strength and excellent corrosion resistance, contain a mixture of softer a phase and a relatively harder martensitic phase/3'. The martensitic phase is generally assumed to have a high strength and low ductility, but the a phase exhibits high ductility. The microstructure of Cu-AI alloys is very complex and only a limited amount of work (compared to the work done on steels) has been carded out to understand the influence of various microstructural features on the deformation characteristics of two phase (a + /3') Cu-AI alloys. 1'2'3 The aim of the present investigation is to 1. assess the suitability of microhardness measurements on individual phases as a microprobe for strength, 2. assess the role of volume fraction and the relative strength of the constituent phases in determining the strength of the two phase alloys, and 3. understand the deformation behavior of two phase Cu-A1 alloys in terms of the behavior of the constituents during straining. II.
EXPERIMENTAL
The alloys were prepared by vacuum induction melting of pure aluminum and copper (three nines purity) and then cast Table I.
Alloy No. 1
Composition Wt Pct AI
Composition and Microstructural Analyses
Metallographically Determined
9
Calculatedfrom Phase Diagram
0
--
15.6 42.2 69.9
2 3 4
9.6 10.2 10.8
15 38 71
5
11.6
100
A.H. YEGNESWARAN, formerly Postdoctoral Fellow, University of Manitoba, is now Scientist, Regional Research Lab., Bhopal 462026, India. K. TANGRI is Professor and Research Director, Metallurgical Sciences Laboratory, University of Manitoba, Winnipeg, Canada. Manuscript submitted December 31, 1982. METALLURGICALTRANSACTIONSA
into slabs of size 120 mm x 16 mm • 16 mm. They were hot rolled (973 K) to 1.2 mm thickness. Samples were cut from these strips and chemically analyzed. The results of the analyses are given in Table I. Tensile specimens of 20 mm gauge length were machined from the rolled strips. The specimens were annealed at 873 K for four hours and then quenched in water (290 K). After suitably polishing the specimens, tensile tests to fracture were performed at room temperature in an Instron machine with a cross head speed of 0.05 cm per minute. In addition, individual specimens were also strained to various levels of plastic strain. Data acquisition and analysis were accomplished with the aid of a computer. Metallographic examination of the specimens was done after polishing and etching in a solution of 5 g FeC13, 5 cc HC1, and 40 cc H20. The volume fraction of second phase was determined by means of areal analysis4 on optical micrographs (determined by superimposing a transparent net on optical micrographs taken at 400 x and counting the squares occupied by the second phase). Hardness measurements were done on the polished and lightly etched surfaces of the undeformed and deformed samples. For macrohardness tests, 2.5 Kg load was used and at least eight readings were taken on each sample, and the average value with the sc
Data Loading...
