| 1. |
- Akhtar, Farid, et al.
(author)
-
A new kind of age hardenable martensitic stainless steel with high strength and toughness
- 2007
-
In: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 34:4, s. 285-289
-
Journal article (peer-reviewed)abstract
- Following analysis of typical age hardenable martensitic stainless steels, a new kind of maragingstainless was developed. The new maraging stainless steel showed high strength, ultimate tensilestrength (UTS) 5 1670 MPa, high toughness, K IC 5 83·9 MPa m1/2 and hardness as high as 478 HVin the age hardened condition. Microstructural study with an optical and transmission electron microscope revealed the typical microstructure of age hardenable stainless steel containing lathmartensite and precipitates. TixNi precipitates were identified by transmission electron microscopy, which were responsible for the increase in mechanical properties after age hardening. The results of natural salt spray test showed that the corrosion resistance of new maraging stainless steel approached to the corrosion resistance of 304L stainless steel.
|
|
| 2. |
- Akhtar, Farid
(author)
-
A new method to process high strength TiCN stainless steel matrix composites
- 2007
-
In: Powder Metallurgy. - 0032-5899 .- 1743-2901. ; 50:3, s. 250-254
-
Journal article (peer-reviewed)abstract
- Layered composites of Ti(C, N) reinforcements and stainless steel have been prepared successfully by powder technology. The layer composite consisted of two layers. The upper layer consisted of TiCN reinforcements and stainless steel as binder material. The lower layer was entirely of binder material (stainless steel). The micro structural study revealed that the upper layer (TiCN/465 stainless steel) showed core–rim microstructure of conventional cermets and the lower layer showed the structure of sintered steel. An intermediate layer was formed due to diffusion reaction of upper and lower layers. This intermediate layer showed a gradient microstructure. The bending strength of the layered material measured was remarkably higher. Ninety per cent increase in the bending strength in the case of 50 wt-% reinforcement in the upper layer was found. The fracture morphologies of upper, lower and intermediate layers are also reported
|
|
| 3. |
|
|
| 4. |
- Akhtar, Farid
(author)
-
An investigation on the solid state sintering of mechanically alloyed nano-structured 90W--Ni--Fe tungsten heavy alloy
- 2008
-
In: International journal of refractory metals & hard materials. - : Elsevier BV. - 0263-4368. ; 26:3, s. 145-151
-
Journal article (peer-reviewed)abstract
- In this study, 90W–7Ni–3Fe heavy alloy was investigated for its microstructure development, mechanical properties and fracture behavior after solid state sintering. The nano-sized powders were synthesized by mechanical alloying (MA). The microstructure of solid state sintered heavy alloys consisted of tungsten matrix. The average tungsten grain size in the range of 1.7–3.0 μm was obtained. It was found that the grain size largely affected the mechanical properties. Tensile strength more than 1200 MPa was achieved at a sintering temperature of 1350 °C. Fracture mechanisms based on microscopical observations on the fracture surfaces were studied. Matrix failure, tungsten-intergranular cleavage and tungsten–matrix interfacial separation were found to be the possible failure mechanisms.
|
|
| 5. |
|
|
| 6. |
- Akhtar, Farid, et al.
(author)
-
Development of Si3N4/ Al composite by pressureless melt infiltration
- 2006
-
In: European PM 2005 conference proceedings. - Shrewsbury : European powder metallurgy association. - 9781899072187 ; 16:3, s. 629-632
-
Conference paper (peer-reviewed)abstract
- Pressureless infiltration process to synthesize Si3N4/ Al composite was investigated. Al- 2%Mg alloy was infiltrated into the Si3N4 and Si3N4 containing 10% Al2O3 preforms in the atmosphere of nitrogen. It is possible to infiltrate Al- 2%Mg alloy in Si3N4 and Si3N4 containing 10% Al2O3 preforms. The growth of the dense composite of useful thickness was facilitated by the presence of magnesium powder at the interface and by flowing nitrogen. During infiltration Si3N4 reacted with Aluminium to form Si and AlN. The growth of composite was found to proceed in two ways, depending on the Al2O3 content in the initial preform. First, preform without Al2O3 content gave rise to AlN, Al3.27Si0.47 and Al type phases after infiltration. Second, perform with 10% Al2O3 content gave rise to AlN-Al2O3 solid solution phase (AlON), MgAl2O4, Al and Si type phases. AlON phase was only present in composite, containing 10% Al2O3 in the Si3N4 preforms before infiltration.
|
|
| 7. |
- Akhtar, Farid, et al.
(author)
-
Effect of adding a type of binder phase on the microstructure, properties and heat treatment of steel bonded TiC cermets
- 2007
-
In: Progress in powder metallurgy. - Uetikon-Zürich : Trans Tech Publications Inc.. ; , s. 1161-1164
-
Conference paper (peer-reviewed)abstract
- Particulate TiC reinforced 465 maraging stainless steel matrix Cermets were processed by conventional P/M. The binder phase was added in the form of elemental powders and master alloy powders. The microstructures, binder phase variation with TiC content and mechanical properties were evaluated. The addition of a type of binder phase largely effects the microstructure and mechanical properties. When a master alloy binder phase was used the microstructure showed interphase debondings, microcracks and large growths of TiC particles. Where as, elemental powders in the composition of binder phases showed defect free microstructure of steel bonded cermets. The binder phase variation from starting composition was observed with increase in wt% TiC content and this variation was higher when the master alloy powders were used as a binder. After heat treatment and aging, an increase in hardness was observed. The increase in hardness was attributed to the aging reaction in maraging stainless steel. The response to heat treatment was decreased with an increase in TiC content due to the shift of binder phase from the starting composition.
|
|
| 8. |
- Akhtar, Farid
(author)
-
Effect of additive Cu-10Sn alloy on sintering Behavior of elemental powders in composition of 465 stainless steel
- 2007
-
In: Journal of Iron and Steel Research International. - 1006-706X .- 2210-3988. ; 14:4, s. 61-74
-
Journal article (peer-reviewed)abstract
- The addition of Cu-10Sn alloy for developing the high strength 465 maraging stainless steel from elemental powders was studied. The sintering parameters investigated include the sintering temperature, the sintering time, and the mass percent of Cu-10Sn. For vacuum sintering, effective sintering occurs at temperature between 1250°C and 1300°C. The maximum sintered density was achieved at 1300°C for 60 min with 3% (in mass percent) Cu-10Sn alloy. More than 3% (in mass percent) Cu-10Sn content and temperature above 1300°C caused slumping of the samples. A maximum density of 7.4 g/cm3 was achieved with 3% (in mass percent) Cu-10Sn content at a sintering temperature of 1300°C for 60 min. A maximum ultimate tensile strength (UTS) of 517 MPa was achieved with 3% (in mass percent) Cu-10Sn content. With content higher than 2% (in mass percent) Cu-10Sn, a maximum increase in the density was observed. The fracture morphologies of the sintered samples are also reported.
|
|
| 9. |
- Akhtar, Farid, et al.
(author)
-
Effect of Cu3P addition on sintering behaviour of elemental powders in the composition of 465 stainless steel
- 2006
-
In: Powder Metallurgy. - 0032-5899 .- 1743-2901. ; 49:1, s. 28-33
-
Journal article (peer-reviewed)abstract
- The addition of Cu3P for developing the high strength 465 maraging stainless steel from elemental powders was studied. The sintering parameters investigated were sintering temperature, sintering time and wt-%Cu3P. In vacuum sintering, effective sintering took place between 1300 and 1350°C. The maximum sintered density of 7·44 g cm−3 was achieved at 1350°C for 60 min with 4–6 wt-%Cu3P. More than 6 wt-%Cu3P content and temperature >1350°C caused slumping of the specimens. The sintered specimens were heat treated and a maximum ultimate tensile strength (UTS) of 767 MPa was achieved with 4 wt-%Cu3P content. The maximum hardness of 45·5 HRC was achieved in heat treated condition with 4 wt-%Cu3P content. Above 4 wt-%Cu3P content increase in density was observed whereas the response to heat treatment decreased. Fracture morphologies of the sintered specimens were also reported. A comparison of sintering behaviour and mechanical properties of elemental powders with prealloyed powders was also given in the present study
|
|
| 10. |
|
|
