Deformation behaviour of two phase materials: Cu-Al system

A study has been made of the deformation behaviour of a series of dual phase (? + ??) and ? + eutectoid Cu-Al alloys. The effect of martensite or eutectoid as the second phase on flow stress, work hardening, and total elongation is described. It is seen that the strengthening effect of martensite becomes greater than that of eutectoid at larger strains. Analysis of stress–strain curves shows that the strain hardening exponent n changes continuously with strain and, as such, the analysis based on the Ludwik equation (? = ?0 + k??pn?) is performed. It is found that alloys showing higher ductility exhibit a three stage behaviour. An explanation for this stage behaviour in terms of the deformation mechanisms involved is presente

Strength and fracture behaviour of metal/matrix particulate composites.

The fracture strengths of various metal matrix particulate composites prepared by a liquid metallurgy technique were analysed. Data on composites from other investigations in which a powder metallurgy or precipitation technique was employed were also included for comparison. The particulate composites were categorized and micromechanical modelling was carried out with due emphasis on fracture mechanisms. It was found that the strength versus volume fraction relation follows a two-thirds power law in the aluminium-graphite system. In the AlAl2O3 system the classical strengthening theory of short-fibre-reinforced composites was found to hold good. In aluminium-glass and AlSiC systems the experimentally determined strengths are higher than the theoretical estimates, while in aluminium-zircon and dual-phase steels the law of mixtures is obeyed. The important roles played by particle-matrix bonding and microstructure are emphasized with a view to improving the development of composites

Dry Sliding Wear Characteristics of Some Zinc-Aluminium Alloys: A Comparative Study with a Bearing Bronze at a Slow Speed

This study reports a few observations made regarding the dry sliding wear behaviour of a newly developed zinc-aluminium alloy. A conventionally used leaded-tin bronze and standard zinc-aluminium alloy have also been characterized under identical test conditions in order to assess the wear performance of the newly developed composition with respect to the converSonal alloys and to understand the factors centrolling the wear response. The study indicates that the bronze exhibited considerably inferior wear behavianr than the zinc-based alloys. In fact, the former revealed "chipping off'' of material to such an extent that the specimens became quite small well before traversing the predeterminea~ sliding distance at a specific pressare. As a result, no seizure pressure could be determined for the bronze. On the contrary, the ~,~inc-based (standard as well as thv modified) alloys showed considerably lower wear rates and better seizure characteristics than the bronze. The wear behaviour of the alloys has been explained on the basis of their microstructural features and further substantiated through the characteristics of the wear surfaces, subsurface regions and debris particles generated during the tests. The analyses of the wear surfaces, subsurface regions and debris particles also enabled the operative wear mechanisms to he underste.od

Tensile Properties of Some Copper and Zinc Based Alloys: Effects of Strain Rate and Test Temperature

This study analyzes the effects of test temperature and strain rate on the tensile properties of some copper-and zinc-based alloys. The copper-based alloys comprised a leaded-tin and an aluminum bronze, whereas the zinc-based alloys were added with various quantities of aluminum. The aluminum bronze attained maximum room-temperature tensile strength, whereas that of the leaded-tin bronze was the least. Among the zinc-based alloys, the one comprising 27.5 mass% aluminum exhibited superior tensile strength, followed by those alloyed with 11.5, 37.5, and 47.5 mass% aluminum in a descending order. Increasing strain rate tended to improve the tensile strength of the alloys. Tensile strength was reduced with an increase in test temperature irrespective of the alloy composition. The aluminum bronze possessed maximum strength regardless of temperature. The leaded-tin bronze attained least strength property at low temperatures, whereas higher test temperatures led to superior strength than the zinc-based alloys. The temperature sensitivity of the strength of the zinc-based alloys decreased with their aluminum content. Tensile elongation of the alloys tended to increase with an increase in strain rate and test temperature. Leaded-tin bronze was least affected in either case. The alloy also attained least elongation irrespective of test conditions. The aluminum bronze showed maximum elongation, at least at high strain rates. In the case of the zinc-based alloys, intermediate range of aluminum concentration led to better elongation. The elongation property of the alloys was affected by temperature in different manners. In a few cases, the elongation initially increased followed by a reduction beyond a specific test temperature, whereas, in other cases, a continuous increase with temperature was noted. The observations made have been discussed in terms of the nature of different microconstituents of the alloys whose effectiveness changes with test conditions. The response of the samples has been further substantiated with their fractographic features and subsurface characteristics

Thermal Immobilization of Cr, Cu and Zn of Galvanizing Waste in the Presence of Clay and Fly Ash

In the present investigation thermal treatment of galvanizing waste with clay and fly ash has been carried out to immobilize Cr, Zn, Cu and other metals of the waste at temperature range 850 degrees C to 950 degrees C. Leaching of the metals from the waste and solidified product was analyzed using toxic characteristic leaching procedure (TCLP). Results indicated that the composition of waste and clay treatment temperature are the key factors in determining the stability of solidified product. After heating at 950 degrees C, the solidified specimens of 10% waste with clay have shown comparatively a high compressive strength and less water absorption. However, a decrease in compressive strength and increase in water absorption were noticed after addition of 15% of waste with clay. The leachability of all the metals present in the waste was found to reduce considerably with the increase of treatment temperature. In the case of Cr and Zn, their leachabilty was found at unacceptable levels from the treated product obtained after heating at 850 degrees C However, their leachability was reduced significantly within an acceptable level after treatment at 950 degrees C. The thermal treatment has shown an increase of re-oxidation trend of Cr (III) to Cr (VI) up to 900 degrees C of heating and this trend became almost zero after heating at 950 degrees C. Addition of fly ash did not show any improvement in strength, durability and leachability of metals from the thermally treated product. X-ray diffraction (XRD) analysis of the product confirmed the presence of mixed phases of oxides of toxic metals