INVESTIGATION ON PREPARATION, CHARACTERIZATION AND PROPERTY EVALUATION OF FGM AL-SI ALLOY CASTINGS PRODUCED BY CAST-DECANTCAST (CDC) PROCESS

Aim of this research paper is to study the microstructural behavior and mechanical properties of Functionally Gradient (FG) layer of Al-Si alloy castings produced by CDC process. The effect of decantation time on the thickness of functionally gradient castings of Al-4.5 wt % Si alloy as an inner layer and Al-Si alloy with 12.5 wt %Si as outer layers was studied by CDC process. The three different combinations of FGM castings were characterized for microstructural and wear behavior using metallurgical characterization and mechanical testing. From the microstructural and wear behavior of FGM casting at outer layer, FG layer and inner layer, it is observed that the FG layer of FGM casting showed very wear resistance compared to other two layers in the FGM casting.

Comminution and Mineral Separation—Geological Input to Metallurgy

Editor’s note: The aim of the Geology and Mining series is to introduce early-career professionals and students to various aspects of mineral exploration, development, and mining, in order to share the experiences and insight of each author on the myriad of topics involved with the mineral industry and the ways in which geoscientists contribute to each. Abstract Communication and collaboration during mine development and operation are essential if the maximum value of a mineral deposit is to be realized, since there are many links between the geology and mineralogy of an orebody and the complex task of an effective plant design. This is only achieved when geologists, metallurgists, and mining and environmental engineers jointly assess the results of metallurgical characterization. This requirement is examined here, albeit for only two of the three metallurgical ore-processing activities—comminution and mineral separation. Wealth is not captured (i.e., is destroyed) unless the most efficient and effective methods for comminuting and separating the mineral(s) of value in a deposit are identified. Benchmarking metallurgical test work requirements for the next mine development based solely on past experience does not address the variability that is unique to the mineralogy of each mineral deposit. Metallurgists are now slowly advancing from using a few (so-called) representative samples to assess the processing characteristics of a deposit to applying metallurgical testing to tens, or hundreds, of samples, with the increase in number of samples allowed by technological advances. More still needs to be done. Identifying the characteristics of different mineralization types of a deposit and grouping it into domains are crucially important. These steps simplify processing by separating ore into relatively few (4–6) types with similar expected metallurgical performance. Understanding what metallurgical tests are measuring and how representative the samples and tests are of the orebody domains are essential considerations for a testing program. No knowledge is bad; some is better or more useful than other. Testing for penalty elements (As, Bi, Hg, F, etc.) and, more importantly, for penalty-element minerals allows their effects to be mitigated during design of the processing plant; this should start during the early exploration stage. Continued evolution of orebody knowledge and confidence in processing ores will lead to better performance of the processing plant, thereby reducing investment risk.

Infuence of Pouring Temperature on Stir Casting of Al/SiC/Mg/Cu Composite

The effect of pouring temperature while preparing Aluminium SiC metal matrix composites, with additional benefits of magnesium and copper through stir casting technique were investigated. The composites were fabricated by mixing 12 wt% of SiC reinforcements,4 wt% magnesium and 2 wt% copper into 6061 aluminium alloy melt at different pouring temperatures (630 ºC, 670 ºC and 710ºC). The addition of magnesium will enhance the wettability of the SiC particles with Al matrix. The inclusion of copper has considerable improvement in strength and hardness of the composite. The microstructure and mechanical properties (tensile strength and hardness) of the Al MMC are evaluated with the corresponding processing parameter, specifically pouring temperature of the cast composite.The metallurgical characterization utilizing optical and scanning electron microscope were observed for the prepared composites. The coarse microstructure and homogenous distribution of SiC particles were appeared within dendrite structures of the composites. The SiC particles has effectively distributed, and higher tensile strength and maximum hardness have occurred in composite at pouring temperature of 670ºC as compared to other composites. The mechanical properties were lower in composites prepared using lesser pouring temperature (630ºC) and significantly decreased for higher pouring temperature (710ºC) of the composites.

Mechanical properties and metallurgical characterization of FSPed TIG and TIG welded AA5052-H32/AA5083-H111 dissimilar aluminium alloys

This work describes the mechanical properties and metallurgical characterization of Friction Stir Processing (FSP) on TIG welded dissimilar AA5052-H32 and AA5083-H111 alloys using ER5356 filler wire. A comparison is drawn between unprocessed TIG weld and FS Processed (FSPed) TIG welded specimen with the identical combination. The fabricated welded joints were investigated By Optical Microscope (OM), Scanning Electron Microscope (SEM) Analysis, Tensile Strength Analysis, and Micro-Hardness testing. The results illustrate the improvement in mechanical properties after FSPed of the TIG welded joint resulting in enhanced tensile strength (224.5 MPa) and hardness (104 HV) in contrast to the unprocessed TIG weld joints with (192.5 MPa) and (70 Hv). In addition, during the mechanical characterization, the FSPed TIG welds show fine grain at the Friction Stir (FS) processed zone with fine grain structures which improves the hardness at the FS zone. The mechanical property of FS joint is superior when compared to the unprocessed TIG weld joint.

Development of NiCrSiBC Weld Hardfacing Approach for P91 Steels Used in Steam Turbine Components

P91 steels are used as substrate material for steam turbine components like bush, valve seat internals, and engineering valves. These components have hardfacing of cobalt-based material to reduce the high temperature wear loss and to improve the surface hardness. However, delamination failure and higher heat affected zone (HAZ) hardness were identified challenges for P91 steels. Hence, this demands the development of a suitable weld hardfacing approach to resolve the said challenges. In this work, NiCrSiBC (Colmonoy 6) has been considered as a hardfacing material to replace cobalt-based Stellite 6 material due to elimination of radiation activity, lower cost, and higher coating hardness. FCAW and PTA techniques were used to deposit buffer layer (SS-309L) and hardfacing layer (NiCrSiBC) respectively. Sample WBL (with deposition of buffer layer) and sample WOBL (without deposition of buffer layer) are considered approaches to study the metallurgical characterization for each case. Higher coating hardness, lower HAZ hardness and lower Fe dilution were observed in sample WBL. Cr7C3, Cr2B, and Cr5B3 hard phases in block shape together with ϒ- nickel matrix solid solution was observed in coating region of sample WBL. Overall, sample WBL approach was considered to overcome weld hardfacing challenges for steam turbine industries.