Hardness and Texture of Electrolytic Copper Processed by ECAP at Ambient and Warm Temperature

Among several severe plastic deformation (SPD) methods, the Equal Channel Angular Pressing (ECAP) process is one of the most popular. This process's main characteristic is producing materials with ultra-fine or nanometric grains. Due to these microstructural changes, it is possible to improve mechanical properties such as strength and ductility. In this perspective, the aim of the present work was to evaluate the variations of the mechanical hardness property associated with microstructural and textural changes of pure copper as a function of its processing by SPD via ECAP. For this, the material was submitted to four passes through routes A (the sample is repetitively pressed without any rotation between each pass) and Bc (the sample is rotated in the same sense by 90° between each pass) at cold and warm temperatures. Through the obtained result, it was verified that the ambient temperature of the Bc route was the one that promoted greater homogeneity in the microstructure and weakening of the texture after the fourth pass. On the other hand, warm processing of copper by ECAP promoted a softening of the samples and a homogeneous distribution of hardness in both routes.

Evaluation of Vickers Hardness Number of Al-Si Alloy Under Heat Treated Conditions

The paper deal with the hardness property assessment of various Al-Si alloys under heat treated conditions. The tested specimens have the compositions of Si with percentages such as 12 18 and 24. The fabrication of the selected composition is carried out by melting the material to the melting temperature of around 800°C. The material is subjected to solutionised heat treatment for 3 hours at 500°C, 520°C and 535°C and quenched in water. Further aging is carried out at 155°C for 2 hours, 5 hours and 8 hours respectively for 500°C, 520°C and 535°C of solution heat treatment condition. The hardness property is evaluated using Vickers Hardness tester as per the standards of ASTM- E92. Thorough comparison of Vickers hardness number is performed among the as- cast and various heat treated environment. Desirable properties of alloy are observed at 520°C solutionised heat treatment & 5 hours of precipitation hardening at 155°C for 18% of Silicon composition. The hardness value decreases due to the increase in percentage of silicon and the values are observed.

Chilling Effect of Inoculation on the Microstructure and Hardness Property of Hypo-Eutectic Grey Cast Iron

The influence of varied weight percent of inoculant (ferrosilicon) on the microstructure and hardness property of hypo- eutectic grey cast iron was investigated. Four sets of chill wedge samples were produced using two chill wedge wooden patterns (W3 1/2 and W4). The first set, the control samples W3 1/2 and W4 were uninoculated. The second, third and fourth sets were inoculated with 1.0wt.%, 1.5wt.% and 2wt.% ferrosilicon respectively to give inoculated samples W3 1/2 and W4. Wedge test was conducted on the samples at the four different points (1, 2, 3 and 4) in accordance with ASTM A367. From the results, microstructures of the control and the inoculated samples were differently influenced by the varied percentage of the inoculant at the four designated points 1, 2, 3 and 4. The average hardness property of the inoculated samples decreases with increasing ferrosilicon addition. Samples W3 1/2 and W4 with 1.0wt.% ferrosilicon revealed high hardness property at chill zone, and hardness property of W3 1/2 was high relative to sample W4 with the values of 34.9 HRA and 30.6 HRA respectively. Similarly, the control samples showed the highest hardness property at the chill zone. Sample W3 1/2 revealed high hardness value of 33.0 HRA relative to sample W4 of 26.8 HRA at the chill zone. Keywords - inoculant; Microstructure; hypo- eutectic; chill zone; hardness property

Asperity level characterization of abrasive wear using atomic force microscopy

Using an atomic force microscope, a nanoscale wear characterization method has been applied to a commercial steel substrate AISI 52100, a common bearing material. Two wear mechanisms were observed by the presented method: atom attrition and elastoplastic ploughing. It is shown that not only friction can be used to classify the difference between these two mechanisms, but also the ‘degree of wear’. Archard's Law of adhesion shows good conformity to experimental data at the nanoscale for the elastoplastic ploughing mechanism. However, there is a distinct discontinuity between the two identified mechanisms of wear and their relation to the load and the removed volume. The length-scale effect of the material's hardness property plays an integral role in the relationship between the ‘degree of wear’ and load. The transition between wear mechanisms is hardness-dependent, as below a load threshold limited plastic deformation in the form of pile up is exhibited. It is revealed that the presented method can be used as a rapid wear characterization technique, but additional work is necessary to project individual asperity interaction observations to macroscale contacts.

Polylactide and its Composites on Various Scales of Hardness

Polylactide (PLA) has become a widely applied material. Its hardness property has, however, not been a subject of intense study. This study attempts to examine the hardness values of Polylactide and its composites on ten hardness scales. Polylactide composites were developed using three reinforcements (i.e., chitosan, chitin, and titanium powders). The compositing method was the melt-blending technique. Vickers microindentation test was carried out on all the developed samples. The experimental values obtained were related to nine (9) other scales of hardness via an online reference interface. Results showed that the Brinell and Rockwell hardness scales agreed, to a large extent, with the experimental values from several studies. Hence, this work can serve as a reference material on the Brinell and Rockwell hardness values of the unreinforced and reinforced composites considered in this study. The developed materials were also represented on the Mohs scale of hardness with unreinforced PLA having the least value of hardness which corresponds to the value of gypsum on the Mohs scale while the PLA reinforced with 8.33 weight (wt.) % of titanium powder has the highest value of hardness corresponding to the value of a material in-between calcite and fluorite. The hardness values obtained on Shore scleroscope could not agree with the experimental values from various studies. Succinctly, the three particulate fillers increased the hardness properties of PLA. The results of this study would go a long way in helping industrialists and researchers in the correct applications of PLA and its composites.

Polylactide and its Composites on Various Scales of Hardness

Polylactide (PLA) has become a widely applied material. Its hardness property has, however, not been a subject of intense study. This study attempts to examine the hardness values of Polylactide and its composites on ten hardness scales. Polylactide composites were developed using three reinforcements (i.e., chitosan, chitin, and titanium powders). The compositing method was the melt-blending technique. Vickers microindentation test was carried out on all the developed samples. The experimental values obtained were related to nine (9) other scales of hardness via an online reference interface. Results showed that the Brinell and Rockwell hardness scales agreed, to a large extent, with the experimental values from several studies. Hence, this work can serve as a reference material on the Brinell and Rockwell hardness values of the unreinforced and reinforced composites considered in this study. The developed materials were also represented on the Mohs scale of hardness with unreinforced PLA having the least value of hardness which corresponds to the value of gypsum on the Mohs scale while the PLA reinforced with 8.33 weight (wt.) % of titanium powder has the highest value of hardness corresponding to the value of a material in-between calcite and fluorite. The hardness values obtained on Shore scleroscope could not agree with the experimental values from various studies. Succinctly, the three particulate fillers increased the hardness properties of PLA. The results of this study would go a long way in helping industrialists and researchers in the correct applications of PLA and its composites.

Evaluation of Thermal Effects on Slag Cement Concrete’s Strength Properties

The physical, chemical, and mechanical characteristics of concrete change with heat-fire. The effect of thermal load on Slag cement concrete output must be measured because of the crucial role of thermal resistance in concrete structure performance and operation. This work examines the thermal resistance of Slag cement concrete. The concrete cubes were produced and cured for 28 days and then subjected to varying temperatures range of 100°C, 150°C, 200°C, 250°C, and 300°C. Hardness and compressive strength were measured at 30, 45, and 60 minutes; the sample results were compared to those of ordinary Portland cement used for the study. The findings of this experiment demonstrate that strength loss was 0.45% at 100 °C, 1.75% at 150 °C, 2.67% at 200°C, 5.98% at 250°C and 12.04 % at 300 °C, the hardness property increased from 100° to 150°C but decreased with higher temperatures. However, average concrete loss at 300 °C exceeds 20 percent of its compressive strength. This means that higher temperatures have adverse effects on concrete strength. From the test, however, it has been noted that there was an insignificant loss of strength of concrete at temperatures below 250°C and however, above 250 °C, a significant loss of concrete strength was observed. The results indicate that slag concrete has a significantly higher thermal resistance potential than traditional concrete and can be used even in industrial applications.