Dayanand Goudar

In the present investigation, microstructural characteristics and dry sliding wear behaviour of T6 heat treated conventionally cast Al-25Mg2Si-2Cu alloy have been discussed. The as cast alloy was subjected to solutionizing at 500°C for 5h and isothermal aging treatment at 190°C for different aging times. The micro structural characterization was studied using Scanning Electron Microscope with EDS analysis. The microstructure of as cast alloy consists of intermetallics of coarse block like sharp edged β-(Mg2Si), θ-(Al2Cu) and Q-(Al-Mg-Cu-Si) in the form of Chinese scripts and needles distributed randomly in the Al-matrix. The microstructure of heat treated alloy shows spheroidization of β phase and fine precipitation of θ-(Al2Cu) and Q phases. The dry sliding wear test was carried out using pin-on-disc machine. Age hardened alloy exhibits high wear resistance and minimum coefficient of friction over the entire range of applied loads and sliding velocities. Furthermore, high wear resistance was observed in the under aged condition compared to over ageing conditions.

ABSTRACT In the present study the effect of copper (Cu) and iron (Fe) on the wear behavior of spray formed Al–28Si alloy has been investigated. The spray formed Al–28Si alloy exhibited equiaxed grain morphology with fine and uniform distribution of Si particles in Al matrix and spray formed Al–28Si–5Cu–4Fe alloy exhibited similar morphology with small needles of β-Al4FeSi intermetallics and globular shaped θ-Al2Cu precipitates spread along the boundaries and junctions of grains. Hot pressing has considerably reduced the porosity in spray formed alloys. On the contrary the microstructure of as-cast Al–28Si alloy consisted of coarse primary and eutectic Si unevenly distributed in Al matrix and that of as-cast Al–28Si–5Cu–4Fe alloy consisted of coarse Si particles, long needles of β-Al4FeSi2 and θ-Al2Cu phases in Al matrix. Spray formed and hot pressed Al–28Si–5Cu–4Fe alloy exhibited higher value of hardness compared to the other alloys. The wear behavior of these alloys under dry sliding conditions showed that the spray formed and hot pressed Al–28Si–5Cu–4Fe alloy exhibited maximum wear resistance and minimum coefficient of friction, while as-cast Al–28Si alloy showed minimum wear resistance and maximum coefficient of friction over the entire range of loads. The high wear resistance of spray formed and hot pressed Al–28Si–5Cu–4Fe alloy is explained in light of its microstructural modifications induced during spray forming and the topography of worn surfaces.

In the present work, Al–30Mg 2 Si–2Cu alloy has been spray formed and subsequently hot pressed for den- sification. The alloy is then subjected to solutionizing and isothermal aging treatments. The microstruc- tural features, hardness and wear behavior of spray formed and secondary processed alloys have been evaluated individually and compared with that of as-cast alloy. The microstructure of spray formed alloy showed refined and globular shaped primary Mg 2 Si intermetallic particles and Al 2 Cu precipitate particles uniformly distributed in Al matrix. The microstructure was refined further after hot consolidation. The microstructure after solution heat treatment appeared similar to that of the spray formed alloy but aging led to a further refinement in the microstructure compared to that of the hot pressed alloy. The evalua- tion of wear behavior of these alloys, under dry sliding condition, showed that the age hardened alloy exhibits maximum wear resistance and minimum coefficient of friction over the entire range of applied load (10–50 N) at a sliding speed of 2 ms 1 followed by hot pressed, spray formed and solution heat trea- ted alloys. The as-cast alloy showed the least wear resistance and highest coefficient of friction. Similar trend has been observed even in their hardness values too. The wear resistance of the alloys is discussed in light of their microstructural modifications induced during spray forming and subsequent secondary processing and also the topography of worn surfaces.

In the present study, the effect of Cu and Mg on the wear behavior of spray formed Al-22Si alloy has been investigated and the same has been compared with that of its counterpart as-cast alloy. Al-22Si and Al–22Si–4Cu–1.7Mg alloys prepared by spray deposition process were hot pressed to reduce the porosity. The microstructures were examined by optical and scanning electron microscopes. The microstructure of spray formed Al-22Si alloy is fine and homogeneous and primary silicon phase distributed in the aluminum matrix evenly are fine and faceted having a mean size of 12 µm. The microstructure of spray formed Al–22Si–4Cu–1.7Mg alloy exhibited equiaxed grain morphology with fine and uniform distribution of both primary and eutectic Si with fine Q-Al-Si-Mg-Cu phase and θ-Al 2 Cu precipitates dispersed evenly in α- Al matrix. In contrast the microstructure of as-cast Al–22Si alloy consisted of coarse plates of primary Si of size 350 µm and eutectic Si needles. The as-cast Al–22Si–4Cu–1.7...

In the present study, Al-28Si, Al-28Si-5Cu-4Fe and Al-28Si-5Cu-4Mg alloys were produced by spray forming and subsequently hot pressed for densification. The effect of alloy composition on the microstructure and mechanical behavior of spray-formed alloys were investigated. The microstructures consist of an equiaxed, nearly spheroidized grain morphology of α-Al matrix. The spray formed alloys exhibited sharply decreased segregation and increased metastable solid solubility and greater volume fraction of Si particles and intermetallic phases. Spray formed Al-28Si-5Cu-4Fe alloy contains Al 2 Cu, Al 5 FeSi along with Si. On the other hand, Al-28Si-5Cu-4Mg alloy showed Al 2 Cu, Al 48 Si 29 Mg 18 and Si. Hot pressing lead to a significant reduction of porosity and partial recrystallization of spray formed alloys. The room temperature tensile tests of spray formed hot pressed alloys showed significant increase in ultimate tensile strength compared to as cast alloys. Spray formed hot pressed Al...

In the present study Al-28Si-5Cu-4Mg alloy has been spray formed and hot pressed for densification. Hot pressing refined the microstructure and reduced the porosity in the spray formed alloy from 10 to 1%. The microstructure of spray formed and hot pressed alloy exhibited equiaxed grain morphology with fine and uniform distribution of both primary and eutectic Si with fine needles of Q-Al 12 Si 7 Mg 4 Fe intermetallics and Chinese script like θ- Al 2 Cu precipitates in α-Al matrix. The size of Si particles ranged from 3–10 µm. In contrast the microstructure of as-cast alloy consisted of coarse primary and eutectic Si, long needles of Q-Al-Si-Mg-Cu-Fe phase and bright grey θ-Al 2 Cu phase in the α-Al matrix. The size of primary Si varied from 30–250 µm. The spray formed and hot pressed alloy exhibited a higher hardness compared to the as-cast alloy. The wear behavior of both the alloys, under dry sliding conditions, showed an increase in the wear rate with an increase in the load. Ho...

This paper focuses on the effect of two-step austempering on abrasion wear characteristics of the ductile cast iron. The single-step (conventional) and two-step austempering were employed for the samples. There were four treatments. For all samples, austenitization at 900 °C was done. The first treatment comprised of conventional austempering at 400 °C. The second one consisted of conventional austempering at 320 °C. The third one consisted of austempering at 400 °C followed by austempering at 320 °C. The fourth one comprised of austempering at 320 °C followed by austempering at 400 °C. The results showed that samples with two-step austempered at 320 °C followed by 400 °C exhibited enhanced abrasion resistance. The reason for this behavior is discussed considering the microstructure parameters.

Modified Al alloys are gaining emphasis in the past few years due to wide range of properties available for the engineering applications. These alloys are manufactured by spray forming process have superior properties over the conventional cast alloys. Hence in this article an attempt has been made to summarize the work that has been carried out in the field of spray forming of hypereutectic Al – Si alloys and with other alloying elements such as Fe, Cu, Mg and Mn. As hypereutectic Al – Si alloys are attractive for the industrial applications due to their low thermal expansion co – efficient and high tribological properties. In this study attention has been paid towards the microstructure, mechanical and tribological properties of the studied alloys. The study of process parameters over the size and shape of the powder in spray forming is other part of this work. The change in properties of spray formed alloys by the working of secondary process is also been considered.

The microstructural characteristics and  mechanical properties of Al–25Mg 2 Si-2Cu alloy were investigated. The alloy produced by spray atomization and deposition techniques followed by hot compression(HC) and age hardening(AGH) at 180oC for 2h and 2h  intervals after the solution heat treatment. The microstructure features of as cast, spray deposited (SD),hot compressed and heat-treated alloys were studied. the results show the microstructure of spray-deposited alloy mainly comprised of a uniform distribution of   intermettalics   ?-Mg 2 Si phase, ?- Al 2 Cu and Q phase in Al-matrix. Eliminating the porosity of deposit and fragmentation of the ? And Q phases is the main features during hot compression. After solution treating and age hardening, the microstructure found to be comprised of mainly Mg 2 Si phase in a fine spherical form. Large quantity of ?- Al 2 Cu phase and Q Phase less than 50 nm in size uniformly distributed in the Al- matrix during aging. These fine ? particles co...

In the present investigation, Al-(20-30%wt) Mg2Si-2Cu alloys were synthesized by spray forming process and further processed by hot pressing for densification. The alloys were further subjected to age hardening heat treatment. The spray formed, age hardened and as-cast alloys were characterized by microstructure and mechanical properties. The microstructure of spray formed alloys exhibited finer and evenly distributed primary β-Mg2Si particles and θ-Al2Cu phase and clusters of discrete and high volume fraction of Q-phase. As-cast alloys mainly consist of large sized polygonal primary β-Mg2Si, coarse Chinese script of Al2Cu and needle shaped eutectic Q-phase. Hot pressing of the spray formed alloy promotes the microstructural refinement, reduction in porosity, fragmentation and redistribution of secondary phases. Artificial age hardened alloys exhibits the large quantity of θ-Al2Cu precipitates less than 2 μm size uniformly distributed in the matrix. The β phase re-precipitates in a ...

Abstract The microstructure characteristics and wear behavior of a spray-deposited (SD) and the hot compressed Al-28Si alloys were investigated and the results were compared with corresponding SD and as-cast alloys. The microstructure, hardness and wear properties of the spray-deposited alloy was studied using X-ray diffraction, optical microscopy, scanning electron microscopy (SEM), microhardness measurement and wear tests. The microstructures of the SD alloy were composed of refined and uniformly distributed primary silicon (Si) and the formation a fine eutectic phase at the inter particle boundaries of an equiaxed grain morphology of the aluminum (Al) matrix. The decrease in the porosity level and further refinement of primary Si and eutectic Si phases in the hot pressed alloy. The wear tests indicate that the hot pressed spray formed alloy showed good wear resistance compared to both the SD and as-cast alloys. The improvement in the wear behavior is discussed in the light of microstructure evolution by the spray-deposition process. The worn surfaces were characterized by SEM-energy dispersive X-ray spectroscopy (EDS).

In the present study, the effect of Sn on the dry sliding wear behavior of spray formed and hot pressed Al–17Si alloy as a function of applied load and sliding speed has been investigated and compared with that of as-cast alloy. The microstructure of spray formed Al–17Si alloy consists of fine and uniformly distributed Si particles and that of Al–17Si–10Sn alloy consists of fine and uniform dispersion of Si particles and ultra-fine Sn particles in α-Al matrix. Coarse and segregated microstructures were observed in as-cast alloys. The wear resistance of spray formed alloys is higher than that of as-cast alloys. The wear resistance of as-cast Al–17Si–10Sn alloy is higher than that of as-cast Al–17Si alloy. The high wear resistance of spray formed Al–17Si–10Sn alloy is discussed in the light of its microstructural features and the nature of worn-out surfaces.

In the present study, the effect of Cu and Mg on the wear behavior of spray formed Al-22Si alloy has been investigated and the same has been compared with that of its counterpart as-cast alloy. Al-22Si and Al–22Si–4Cu–1.7Mg alloys prepared by spray deposition process were hot pressed to reduce the porosity. The microstructures were examined by optical and scanning electron microscopes. The microstructure of spray formed Al-22Si alloy is fine and homogeneous and primary silicon phase distributed in the aluminum matrix evenly are fine and faceted having a mean size of 12 µm. The microstructure of spray formed Al–22Si–4Cu–1.7Mg alloy exhibited equiaxed grain morphology with fine and uniform distribution of both primary and eutectic Si with fine Q-Al-Si-Mg-Cu phase and θ-Al2Cu precipitates dispersed evenly in α-Al matrix. In contrast the microstructure of as-cast Al–22Si alloy consisted of coarse plates of primary Si of size 350 µm and eutectic Si needles. The as-cast Al–22Si–4Cu–1.7Mg ...