Semisolid Sinter-Forging of Hyper-Eutectic Al-Si Alloy Using Rapid Resistance Heating

2010 ◽  
Vol 654-656 ◽  
pp. 1408-1411
Author(s):  
Seijiro Maki ◽  
Masayuki Noda ◽  
Eitoku Nakanishi
Keyword(s):  
Mechanical Properties ◽  
Alloy Powder ◽  
Green Compact ◽  
Resistance Heating ◽  
Heating Condition ◽  
Semisolid State ◽  
Sinter Forging ◽  
Primary Si

In casting of hyper-eutectic Al-Si alloys, primary Si grains often grow, which deteriorates mechanical properties of the castings. In this study, an attempt was made to obtain hyper-eutectic Al-Si alloy parts without coarse primary Si grains by taking another route of sinter-forging. The sinter-forging taken up here is semisolid one. In this sinter-forging, a green compact billet of hyper-eutectic Al-25mass% Si alloy powder is rapidly resistance-heated into a semisolid state to promote the sintering and then upset-forged into a disc shape, and the performance was examined by paying special attention to the behavior of primary Si grains in the relation to the resistance heating condition.

Porosity Development and Modification in Al-Si Alloys: Effect of P and Sr

2019 ◽  
Author(s):  
J. Campbell ◽  
Murat Tiryakioğlu
Keyword(s):  
Mechanical Properties ◽  
Liquid Metal ◽  
Crack Size ◽  
Primary Si ◽  
Interdendritic Flow ◽  
Oxide Bifilms ◽  
Lower Temperature ◽  
Porosity Development ◽  
Silicon Particles ◽  
Crystalline Growth

The benefits of Sr additions to Al–Si alloys to modify the eutectic are often impaired by the development of porosity, sometimes to the degree that benefits are negated. Experimental reports are reviewed in this paper, suggesting an explanation in terms of the oxide population in the melt. The unmodified silicon particles are nucleated by AlP, which has in turn nucleated on oxide bifilms. The oxide bifilms, which are essentially cracks, are straightened by the crystalline growth of Si particles, leading to increased crack size and consequently reduced mechanical properties. The addition of Sr improves properties by suppressing the formation of Si on bifilms and thereby preventing the straightening of the pre-existing cracks. Si is now forced to precipitate at a lower temperature as a coral-like eutectic. Unfortunately, the bifilms are now freed (the primary Si particles no longer exist to grow around and sequester the bifilms), remaining in suspension in the liquid metal, allowing them to act to block interdendritic flow and aid the initiation of the formation of pores, countering the benefits of the improved structure.

scholarly journals Enhancement of the Mechanical Properties in Al–Si–Cu–Fe–Mg Alloys with Various Processing Parameters

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2150 ◽  
Author(s):  
Su-Seong Ahn ◽  
Sharief Pathan ◽  
Jar-Myung Koo ◽  
Chang-Hyun Baeg ◽  
Chan-Uk Jeong ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Electron Microscope ◽  
Silicon Content ◽  
Compositional Analysis ◽  
Processing Parameters ◽  
Silicon Phase ◽  
X Ray ◽  
Primary Si ◽  
Transmission Electron ◽  
Eutectic Si

In this research, various processing conditions were implemented to enhance the mechanical properties of Al-Si alloys. The silicon content was varied from hypoeutectic (Si-10 wt.%) to eutectic (Si-12.6 wt.%) and hypereutectic (Si-14 wt.%) for the preparation of Al-XSi-3Cu-0.5Fe-0.6 Mg (X = 10–14%) alloys using die casting. Subsequently, these alloys were hot-extruded with an optimum extrusion ratio (17:1) at 400 °C to match the output extruded bar to the compressor size. An analysis of the microstructural features along with a chemical compositional analysis were carried out using scanning electron microscope along with energy dispersive X-ray spectroscopy and transmission electron microscope. The SEM micrographs of the extruded samples displayed cracks in primary Si, and the intermetallic (β-Al5FeSi) phase was fragmented accordingly. In addition, the silicon phase was homogenously distributed, and the size remained constant. The mechanical properties of the extruded samples were enhanced by the increase of silicon content, and consequently the ductility decreased. By implementing proper T6 heat treatment parameters, coherent Al2Cu phases were formed in the Al matrix, and the Si phase was gradually increased along with the silicon content. Therefore, high tensile strength was achieved, reaching values for the Al-XSi-3Cu-0.5Fe-0.6Mg (X = 10–14%) alloys of 366 MPa, 388 MPa, and 420 MPa, respectively.

Selective laser melting of magnesium AZ31B alloy powder

2019 ◽  
Vol 26 (2) ◽  
pp. 249-258 ◽  
Author(s):  
Andrzej Pawlak ◽  
Patrycja E. Szymczyk ◽  
Tomasz Kurzynowski ◽  
Edward Chlebus
Keyword(s):  
Mechanical Properties ◽  
Selective Laser Melting ◽  
Alloy Powder ◽  
Az31 Alloy ◽  
Optimum Process ◽  
Laser Melting ◽  
Content Type ◽  
Fine Grained ◽  
Az31b Alloy ◽  
Hot Rolled

Purpose This paper aims to discuss the results of material tests conducted on specimens manufactured from AZ31 alloy powder by selective laser melting (SLM) technology. The manufactured specimens were then subjected to porosity assessment, microstructure analysis as well as to mechanical and corrosion tests. Design/methodology/approach SLM process was optimized using the design of experiments tools. Experiments aimed at selecting optimum process parameters were carried out in accordance with a five-level rotatable central composite design. Findings The porosity results showed very low values of <1 per cent, whereas mechanical properties were close to the values reported for the reference wrought AZ31 alloy in hot-rolled state. A fine-grained microstructure was observed with a large range of grain size, which enhanced the material’s mechanical properties. Corrosion characteristics of the SLM-manufactured material exceed those determined for the wrought material. Originality/value The results presented in this paper drive interest in magnesium alloys used in additive manufacturing processes. Low porosity, good mechanical properties, form of the microstructure and, most importantly, improved corrosion characteristics suggest that SLM provides great potential for the manufacture of ultralight structures, including resorbable metallic implants.

scholarly journals Effects of Compaction Velocity on the Sinterability of Al-Fe-Cr-Ti PM Alloy

Materials ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 3005 ◽  
Author(s):  
Xianjie Yuan ◽  
Xuanhui Qu ◽  
Haiqing Yin ◽  
Zhenwei Yan ◽  
Zhaojun Tan
Keyword(s):  
Mechanical Properties ◽  
High Velocity ◽  
Alloy Powder ◽  
Sintered Density ◽  
Ti Alloy ◽  
Maximum Elongation ◽  
Nitrogen Gas ◽  
High Velocity Compaction ◽  
Ti Powder ◽  
Particle Boundary

In this research, the effects of the compaction velocity on the sinterability of the Al–Fe–Cr–Ti powder metallurgy (PM) alloy by high velocity compaction were investigated. The Al–Fe–Cr–Ti alloy powder was compacted with different velocities by high velocity compaction and then sintered under a flow of high pure (99.999 wt%) nitrogen gas. Results indicated that both the sintered density and mechanical properties increased with increasing compaction velocity. By increasing the compaction velocity, the shrinkage of the sintered samples decreased. A maximum sintered density of 2.85 gcm−3 (relative density is 98%) was obtained when the compaction velocity was 9.4 ms−1. The radial and axial shrinkage were controlled to less than 1% at a compaction velocity of 9.4 ms−1. At a compaction velocity of 9.4 ms−1, sintered compacts with an ultimate tensile strength of 222 MPa and a yield strength of 160 MPa were achieved. The maximum elongation was observed to be 2.6%. The enhanced tensile properties of the Al–Fe–Cr–Ti alloy were mainly due to particle boundary strengthening.

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