Volume 50, Issue 4

If a specimen has been cold worked, or it did not recrystallize after hot working, the grains will not be equiaxed and extra care must be taken when assessing the specimen's grain size. Always test a longitudinally oriented plane first to determine if the grains are, or are not, equiaxed. In this work, a low-carbon sheet steel was tested in the as-received condition (reportedly annealed), and after cold reductions in thickness of 12, 30 and 70 %. Above 70 % reduction, it can be quite difficult to reveal the ferrite grain boundaries well enough to get a precise measurement. Measurements were made on the three principal planes using the Jeffries planimetric method, the Abrams three-circle intercept method and the intercept method using directed parallel test lines. Grain elongation was assessed using the simple anisotropy ratio and the Saltykov degree of orientation method.

Light-alloy castings often exhibit variability in the fracture sensitive properties such as ductility that does not necessarily correlate to the global average microstructural parameters such as dendrite cell size and porosity volume fraction in the three-dimensional microstructure. Nonetheless, in numerous such cases, the variability in the fracture sensitive properties does correlate to the variability in the local distributions of microstructural features and processing defects because the fracture path preferentially goes through the regions containing large concentrations of the defects and/or microstructural extrema. This paper presents the results of a detailed quantitative metallography and quantitative fractography based investigation of the relationships between microstructure and variability in uniaxial tensile ductility of the tensile test specimens drawn from very large size Al alloy automotive component castings fabricated using tilt-pour permanent-mold casting process. The percent tensile ductility e shows strong quantitative correlation with the area fraction of the porosity f in the corresponding fracture surfaces, which can be represented by the following power-law relationship, where e 0 and n are empirical constants.

This paper is a follow-up and update of the article “Titanium and Its Alloys” in Volume 9 of the ASM Handbook, Metallography and Microstructures [1]. Because of its inherent characteristics, titanium is one of the more difficult metals to prepare for metallographic examination, as illustrated below. The challenge is to understand and minimize metallographic preparation artifacts through an understanding of their cause. They will be introduced if the wrong preparation steps and/or etching techniques are applied. For example, if one used the metallographic preparation process for a body centered cubic tempered martensitic steel, etching of Ti and its alloys would not reveal the true structure. This article covers the effect of etchant selection and etching time, the effect of remnant mechanical deformation and cold work produced during specimen preparation, the influence of interstitial contamination and enrichment on the microstructure, and the effect of these problems on heat affected zones.

Copper piping systems for HVAC (Heating Ventilation Air Conditioning) are used to transport heating and cooling water in high rise buildings. Commercial and residential plumbing has a design life that must be specified with respect to the water quality parameters associated with the geographic location. Stress corrosion cracking has been identified as one of the failure mechanism normally occurring in the infancy of the life of the systems that is highly associated with contamination. A metallurgical analysis of the characteristics of typical cold worked tubing, used in copper piping, with insulation, contamination and crack morphology are presented.