Comparative Study of Surface Contaminated Layer on Titanium Aluminum Alloy and Titanium Alloy Investment Castings

A comparative study of the surface contaminated layer formed by chemical reaction between ceramic-mold and titanium aluminum alloy castings or titanium alloy castings were carried out. The morphology, thickness and hardness of the surface contaminated layer were characterized by means of metalloscopy and microhardness measurement. The results show that surface contaminated layers formed between Ti-Al alloy castings and ceramic-mold, also formed between Ti alloy castings and ceramic-mold. The surface contaminated layers of Ti-Al alloy castings were continuous and compact, their thickness was about 0~90 μm. The surface contaminated layers of titanium alloy castings were not even, their thickness was 0~900 μm. Titanium alloy is more liable to react with the ceramic -mold than the Ti-Al alloy.

Application of Image Analysis Method Combined with Microhardness Measurement to Determine Phase Fractions

We have determined different phase fractions from microscopy images using semi-automated image analysis fitting technique, and in addition we have classified each phase according to its hardness. The distribution of grayscale pixels of different phases is first characterised separately for each phase, which are sampled from the microscope image. After this the distributions of the separate phases are fitted to give the corresponding distribution of the whole image. The microhardness measurement provides reliability on the classification of the different phases to ferrite, bainite or martensite. In addition to describing the applied techniques in detail, we present the results obtained from the analysis for one steel subjected to isothermal holding experiments at different temperatures.

Local mechanical properties of explosively welded AA2519-AA1050-Ti6Al4V layered material

The study presents the results of tests of local static and cyclic properties of an explosively welded AA2519-AA1050-Ti6Al4V layered material. In order to perform the analysis, tests were carried out with the use of microspecimens collected from 10 layers of AA2519-AA1050-Ti6Al4V material. Additionally, the determined static properties were compared with the results of an analysis based on microhardness measurement. Based on the test results, slight differences in static properties were found for particular layers of the material as well as a distinct softening of the AA2519 layer in relation to the base values. It was also found that the application of microhardness measurement for analysis of static properties can lead to their overestimation. Cyclic properties were described by the Ramberg-Osgood model. As in the case of static properties, the cyclic properties of particular layers of AA2519-AA1050-Ti6Al4V material differ insignificantly. The tests of cyclic properties showed that application for their description the Ramberg-Osgood model, based on parameters determined for whole range of plastic strains, can lead to significant errors in the modeling of a layered material. The cyclic instability of Ti6Al4V and AA2519 alloys has a significant influence on the parameters to be determined for material models of the analyzed material.

Investigation of Strain Hardening in Aluminum Alloy Sheared Sheet Based on Microhardness Measurement and FEM Analysis

This research was carried out to investigate the strain hardening in an aluminum alloy worksheet caused by punch/die shearing by means of microhardness measurement and finite element method (FEM) analysis. To examine the strain-hardened zone at the sheared edge of a worksheet, a 0.36 mm thick AA4047 aluminum alloy cut by punch/die shearing was subjected to microhardness measurements. In addition, a two-dimensional FEM model was developed and used to simulate the shear cutting of the aluminum alloy worksheet. The fundamental shear cutting parameters, punch/die clearance, cutting tool wear, and friction at the worksheet/tool interfaces were numerically varied and simulated. From the investigation results, the strain-hardened zone was observed by hardness measurement. The size of the zone significantly varied under different cutting parameters. From the simulated stresses at the sheared zone, the variation of the width of the strain-hardened zone with respect to cutting parameters was determined by the maximum principal stress on the worksheet being sheared.

The Microhardness as an Express Method for Estimation the Depth of Metal Particle Distribution

By measurement of microhardness of silver layer on polyimide films and its reduction after removing the stress, the depth of silver distribution in the polyimide films was calculated. A significant hardening of Kapton 100 HN films was observed especially for cobalt-impregnated materials, which was about 10 μm. The distribution of silver in the film layers was obviously deeper that manifested as entirely lower hardening at microhardness measurement. Because of the initial microhardness of Upilex it was observed strong hardening of the effort, which was led to shallow distribution of metals in the films. For example, Cometallized films showed 5 μm distribution in the top film layers. Such method could allow precisely and rapidly estimating the distribution of metal particles impregnated in metallized polymeric materials.

Surface Engineering of Stainless Steels: Role of Surface Mechanical Attrition Treatment (SMAT)

Surface mechanical attrition treatment (SMAT) technique has became popular to develop a nanostructured surface layer on metallic materials for upgrading their overall properties and performance. In this paper, we have presented the SMATing behavior of low stacking fault energy material like AISI 304 using optical microscopy, SEM, microhardness measurement and XRD analysis. SMATing was performed for 15, 30, 45, 60, 75, 90 min by using hardened bearing-steel balls (size: 5.7 mm diameter, hardness: 500HV0.1) at 50 Hz vibrating frequency. XRD analysis indicated the lowest grain-size of about 8.6 nm in the surface region of specimen SMATed for 60 min. In comparison with the non-SMATed specimen, 17 times increase in the dislocation density and 4 times increase in the micro-strain were observed in this SMATed specimen. Improvement in the surface-hardness due to the SMAT was almost two times hardness before SMAT was 190 HV0.1 and after SMAT it was 400 HV0.1. There is a gradual decrease in the hardness value across the cross-section of the specimen, and core-hardness value was reached after 300 μm depth below the surface. XRD results indicated the possibility of martensitic phase transformation at the surface during SMATing of AISI 304 steel. SMATed AISI 304 specimens showed good thermal stability at 550°C for 6 h which was confirmed by microhardness measurement