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Part A: Precipitation hardening in a TI-CU alloy Part B: The structural and nagnetic Properties of some quarternary alloys of Mn₆₀oA1ₓZn₂₀-ₓC₂₀ and Mn₆₀GaₓZn₂₀-ₓC₂₀

University of British Columbia

The decreasing solid solubility limit at the titanium-rich end of the titanium-copper constitutional diagram suggests the possibility that titanium-rich alloys may be age-hardenable. However, results obtained by previous investigators, using lump samples, show that after quenching from 790°C the age-hardening of an alloy containing 1,7 percent copper is very light while a 0.8 percent copper alloy decreases in hardness, during heat treatment at 400°C. It was believed possible that powder samples of alloys might show different results from the lump samples used by previous investigators. Consequently, a 1.90 percent copper alloy was made by the technique of levitation melting, checked for homogeneity, and filings of 48-65 Tyler screen size were cut from it for aging experiments. Hardness readings do show a hardness peak at aging temperatures of 400°C, 450°C, and 500°C and thus indicate that the titanium-copper alloy is susceptible to age-hardening treatments. Interest in the Mn₆₀A1xZn₂₀_ₓC₂₀ and Mn₆₀GaₓZn₂₀-ₓC₂₀ systems results from pregious studies of Mn-A1-C, Mn-Zn-C, and Mn-Ga-C systems; in particular the alloys near compositions Mn₆₀A1₂₀C₂₀, Mn₆₀Zn₂₀C₂₀ and Mn₆₀Ga₂₀C₂₀. The saturation magnetization (σ) versus temperature (T) curve for alloys near the compositions Mn₆₀A1₂₀C₂₀ and Mn₆₀Ga₂₀C₂₀ shows normal ferromagnetic behaviour from 0°K to the Curie points of the alloys. Alloys near the composition Mn₆₀Zn₂₀C₂₀, on the other hand, have abnormal behaviour as they experience a maximum in the σ-T curve in the neighbourhood of -40°C. Reasons for investigating the Mn₆₀A1Zn₂₀-xC₂₀ andMN₆₀GaₓZn₂₀-ₓC₂₀ systems were: 1. to provide further data regarding the presence of abnormal behaviour in Mn₆₀Zn₂₀C₂₀ and of normal behaviour in Mn₆₀A1₂₀C₂₀ and Mn₆₀Ga₂₀C₂₀. (i.e. alloys near these compositions). 2. to suggest how the valency of the cube-corner atom affects the normal ferromagnetic moment of these alloys. However, investigation of these systems has lead to even more complicated phenomena, and the above two items remain, to a large extent, unsolved.

Text

2012-01-31

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http://hdl.handle.net/2429/40404

Mining Engineering

University of British Columbia

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