METALLURGY AND BAILLIEU LABORATORY
D. PHYSICAL METALLURGY (12) Solid Solution of Mercury in Lead
Worker: /. Neill Greenwood
Work on the phase diagram of alloys containing up to 50 per cent mercury using thermal, hardness and microscopic methods has re- vealed several discrepancies with existing diagram. Thc work is being continued.
(13) Investigation of the Titanium-Aluminium System in the Range 0 — 25% Aluminium
Workers: D. W. Borland and H . W. Worner (supervisor)
The problem of achieving homogeneity in these alloys has been further studied. Because of their brittle behaviour, it is not possible to follow the usual technique of hot working and annealing, and it is therefore necessary to anneal at temperatures in the vicinity of
i5oo°C. Apparatus for annealing at these temperatures by induction heating in vacuo has been constructed.
(14) Properties of Titanium Alloys Worker: J. W. Suiter (C.S.I.R.O.)
The effect of additions of niobium to a titanium-aluminium alloy have been studied. Although additions of niobium increase the
112 F A C U L T Y OF E N G I N E E R I N G
strength at low temperatures, they have little effect on thc strength at temperatures above 500°C. I f the alloy contains io at. per cent niobium then the properties at low temperatures can be improved by heat treatment. Small increases in impurity content increase thc strength of these alloys appreciably without seriously affecting the ductility.
(15) Relationship Between Structure and Properties of Steels Worker: H. Muir
This project has been continued from the previous year. Methods of electropolishing ingot iron and plain carbon steel specimens have been developed, with a view to studying the initiation and propa- gation of Luders bands on polished surfaces. Preliminary tests have been made using a small tensile testing machine specially designed to work on the stage of a metallurgical microscope. Microscopic observations are being correlated with macroscopic strain measure- ments.
(16) Carbon Segregation in Steel Worker: D. G. Walker
Calculations show that the phenomenon of carbon segregation during tempering of quenched pearlitic manganese steel can be re- lated directly to the influence of manganese rich segregates on the carbon activity. I t is hoped to extend this work to cover cases where phosphorus and silicon arc responsible for the carbon migration.
(17) Ageing Effects in Rolled Brass
Workers: M . L . Gillin, H . Muir and J. S. Hoggart (supervisors) The purpose of this project is to investigate a rapid ageing effect previously observed during deep drawing tests in rolled 70:30 brass.
The effect has been investigated by the use of elastic limit and resistivity measurements and microscopic methods. The investigation has shown that the elastic limit is sensitive to the ageing effect and that thc effect involves a marked drop in elastic limit for the first two to three days after rolling, followed by a gradual increase to above the original value. Transverse specimens differed slightly f r o m longitudinal specimens in ageing characteristics. Marked strain re- laxation effects were also observed during the first few days after rolling.
A theory has been devised to account for the ageing effect, but more work will be required to substantiate it. I t is hoped to con- tinue the project on a part-time basis.
(18) The Study of Slow Deformation of Lead as a Contribution to the Understanding of Creep
Worker: R. C. Gifkins (C.S.I.R.O.)
M E T A L L U R G Y A N D H A f L L I E U L A B O R A T O R Y 113
The work described previously has been continued; in particular the study of boundary migration has been re-interpreted quantita- tively. Dislocation densities have been taken as the driving force and oxygen segregated to the boundaries as the rate-controlling factor.
In order to assess various theoretical approaches, it is desirable to know the stacking-fault energy of lead; some preliminary measure- ments of twin-boundary/grain-boundary energies have been made.
A review of mechanisms of intergranular fracture, with some new quantitative treatments, has been made.
(19) The Boundary Sliding during Creep of Lead Bi-Crystals Workers: P. R. Strutt and R. C. Gifkins (C.Sd.R.O.) (supervisor) The work has been continued from previous years. Bi-crystal specimens have been tested in creep at various stresses and tem- peratures. Measurements of creep within each crystal and across the boundary have been made and compared with the sliding measured parallel and perpendicular to thc applied stress. Information on the zone associated with sliding and on activation energies has been obtained. The work is continuing with further studies of the effect of temperature and orientation differences between the crystals.
(20) The Study of Creep of Lead using an X-ray Micro-beam Technique
Workers: H. F. Ryan (C.Sd.R.O.) and R. C. Gifkins (C.S.I.R.O.) (supervisor)
The micro-beam equipment has been calibrated and preliminary measurements of depth of penetration of the beam and thc 'particle' size of cold-worked specimens made. I t is intended to measure the effect of rate of strain on thc particle size and then to study the local conditions near grain boundaries during creep.
(21) Fracture of Metals by Fatigue Worker: W. A. Wood
The techniques previously developed have been applied to more detailed study of fatigue in copper and brass. The further work shows that fatigue fracture may arise from two distinct mechanisms.
The first, predominating when rhe fatigue cycles impose large plastic amplitudes and corresponding to the early part of an S/N curve when specimens have short lives, causes fracture by building up high internal stresses. The second, predominating when thc cycles impose small plastic amplitudes and corresponding to the late part of the S/N curve when specimens have long lives, causes fracture by (a) producing abnormal lattice distortions along limited lengths of slip planes, (b) causing these limited active zones to develop at
114 F A C U L T Y OF E N G I N E E R I N G
the specimen surface sharp contour changes ranging from notches to peaks, (c) permitting the notches to penetrate the limited active zones and turn them into non-propagating fissures of correspond- ingly limited length, and (d) finally giving rise to a propagating crack through collapse of metal thus saturated with fissures. The mechanisms have been correlated with solid-state theory.
(22) The Mechanism of Fatigue Failure in Lead
Workers: K. U. Snowden (Broken Hill Associated Smelters) and J. Neill Greenwood (supervisor)
Work has continued on the effects of alternating strain on poly- crystalline lead specimens tested in different gases and in air at re- duced pressures. The dependence of fatigue life on oxygen partial pressure is being investigated further as previous work had shown that oxygen has a marked effect on thc fatigue properties. Preliminary results suggest that oxygen partial pressures down to about o-iomm.
mercury cause a significant reduction in fatigue life.
Observations on the microstructure, made in conjunction with the above work, have shown that above o i o m m . mercury cyclic strain- ing causes slip, anisotropic grain-boundary migration and thc early formation of intcrcrystalline cracking. Below about o-io mm. mercury similar changes were found except that boundary cracking was sup- pressed and grain-boundary extrusion took place in the form of fila- ments and eruptions.
(23) Cathodic Etching of Metals
Workers: Natalie F. Wagner and J. Neill Greenwood (supervisor) The aims have been to elucidate thc factors affecting cathodic etching: of metals, and to develop the process as a universal means of etching metals for metalloeraphic purposes. The rate of etching has been found to increase with mass of bombarding; gas ions. Work hardened metals seem to show slightly increased etching rates.
Cathodic etching has been found satisfactory for all metals investi- gated, and has been found particularly useful for metals and other materials difficult to etch chemically—e.g. Chromium, Lead-Mercury alloys, Nimonic alloys and some ceramic materials. This work has been continued from thc previous year and is now almost complete.
(24) Production and Properties of Pure Silicon Workers: R. McPherson and H. Muir (supervisor)
The preparation of single crystal rods of silicon by floating zone melting has been continued. A number of methods of producing the initial rods of silicon have been attempted. The crystallization of silicon from a liquid aluminium-silicon alloy in a temperature gradient has been tried as a method of producing suitable silicon rods.
M E T A L L U R G Y A N D B A I L L I E U L A B O R A T O R Y 115
(25) Application of Ultrasonic Waves in Metallurgy Worker: D. G. Walker
Construction of a modified ultrasonic generator has been con- tinued. Experimental work on thc effect of ultrasonic agitation in electro-plating is expected to begin soon.
(26) Effect of Molybdenum on Ductility of Copper Electrodeposits Workers: G. V. Cullen and John H. Hcnsler (Industrial Research
Section)
In a process developed elsewhere for the electrowinning of copper from leach solutions of roasted concentrates, the electrodeposits were seriously embrittled by the presence of molybdenum in amounts of thc order of 0-050 per cent and less. X-ray diffraction studies of synthetic copper-molybdenum melts as well as the electrodeposits confirmed other workers' findings of no solid solubility of molyb- denum in copper. A special leaching technique indicated a con- centration at grain boundaries. Vacuum fusion and gas analysis showed the presence of abnormal amounts of hydrogen, possibly associated as water. It was concluded that thc gas was the direct cause of stresses causing brittleness and that molybdenum facilitated the retention of hydrogen (or water) in the deposit.
(27) Atomization of Liquid Metals
Workers: G. V. Cullen and John H. Hensler (Industrial Research Section)
A start was made on an investigation concerning the mechanism of the formation of metal shot by impingement of water or air on a stream of liquid metal. I t is hoped to get a clearer understanding of thc effect of temperature, viscosity and composition of thc metal as well as thc influence of pressure, velocity and geometry of the atomizing medium.
PUBLISHED WORK
1. CULLEN, G. V.— The Organization of Research. /. Aust. Inst.
Metals 3 (1): 1-22 (May 1958)
2. GIFKINS, R. C.— Oxygen as an Impurity in High-Purity Lead.
Acta Mctallurgica 6: 132-3 (1958)
3. The Optical Examination of Metals. /. Aust. Inst.
Metals 3; 143-56 (1958)
4. •— Renewed Creep in Lead-Thallium Alloys Prestrained by Extensive Tertiary Creep. Bull. hist. Metals 4: 117-18 (1958) 5. GREENWOOD, J. N . — The Solid Solution of Gallium in Lead.
/ . Inst. Metals 8 j : 91-3 (1958/9)
116 F A C U L T Y OF E N G I N E E R I N G
6. KENNEDY, G. L . and EVANS, D. G.— Research in the Develop- ment of a Metallurgical Fuel from Brown Coal. / . Aust. Inst.
Metals 3: 61-75 0958)
7- Metallurgical Fuel from Victorian Brown Coal. /. Inst.
Fuel 31: 242-7 (1958)
8. MCPHERSON, R.—The Metallurgy of Silicon. /. Aust. Inst.
Metals 3: 250-9 (1958)
9. Mum, H.—Thc Failure of Metals Under Load. /. Aust. Inst.
Metals 3: 37-60 (1958)
10. SNOWDEN, K. U . and GREENWOOD, J. N . — Surface Deformation Differences between Lead Fatigued in A i r and in Partial Vacuum. Trans. Amer. Inst. M i n . Metall. Engrs 212: 626-7 ('958)
11. SNOWDEN, K. U . — Grain-Boundary Extrusion and Deformation During the Fatigue of Lead in a Partial Vacuum. Phil. Mag.
3 : 1411-12 (1958)
12. SUITER, J. W.— Properties of Titanium-Niobium Alloys. Bull.
Inst. Metals 4: 104-5 ('958)
13. Some Effects of Pressure on Consumable Electrode Arc Melting. / . Electrochem. Soc. 106: 47 (1959)
14. WOOD, W. A.— Formation of Fatigue Cracks. Phil. Mag. 3:
692-703 (1958)
THESES PASSED FOR HIGHER DEGREES
DOCTOR OF PHILOSOPHY
1. MILLER, D. R. Internal Friction in Titanium and Its Alloys
A low frequency torsion pendulum of high sensitivity was used to examine the variation of internal friction and rigidity modulus with temperature for titanium and alloys of titanium with oxygen, nitrogen, aluminium and zirconium. Internal friction in high purity titanium (clectrolytically refined) was low at temperatures between 20°C and 300°C but at higher temperatures it increased rapidly. Measure- ments at temperatures above 500°C were difficult to interpret with this material because of the effect of creep in the specimen under the stress imposed on it by the torsion bar, and at still higher temperatures (540°C) internal friction became amplitude dependent so that measurements had to be discontinued.
In material of somewhat lower purity (iodide-refined titanium) a peak in thc internal friction curve could be resolved at about 4io°C and since this peak increased in height with increasing oxygen content, it was ascribed to the presence of oxygen in thc titanium. By contrast, nitrogen had little effect on the internal friction curves and it was onlv in an alloy containing approximately 5 atomic percent nitrogen, that an additional internal friction peak, which was only partially resolved, could be detected at about 55o°C.
Thc oxygen peak was markedly affected hy the addition of aluminium and zirconium to iodide refined titanium. In thc aluminium alloys the peak height was unchanged but thc peak temperature was increased and the activation energy associated with it was reduced. In the zirconium alloys, on the other hand, the oxygen peak was progressively increased in height as the zirconium content increased while its temperature and activation energy were both reduced.
These observations and some anomalies in the variation of rigidity modulus with temperature have been explained in terms of a dislocation model based on the forma- tion and movement of Cottrell atmospheres of oxygen atoms around dislocations in the metal.
M E T A L L U R G Y A N D B A I L L I E U L A B O R A T O R Y 117 MASTER OF SCIENCE
i . BLANKS, R. F. The De-copperizing of Lead and Refining die Low Melting Metals
3. BRINSON, G. A Study of Recrystallization i n Zinc by Direct Observation
4. STRUTT, P. R. Creep and Boundary Sliding in Lead Bi-crystals MASTER OF ENGINEERING SCIENCE
5. ELI.SON, D. B. Correlation of Properties of a Temper-Brittle Steel
6. THOMSON, P. F. The Promotion of Fluid Lubrication in Wire Drawing