scholarly journals Sinter Hardening PM Steels Prepared through Hybrid Alloying

2021 ◽  
Vol 76 (2) ◽  
pp. 105-119
Author(s):  
S. Geroldinger ◽  
R. de Oro Calderon ◽  
C. Gierl-Mayer ◽  
H. Danninger
Keyword(s):  
Cross Sections ◽  
Master Alloy ◽  
Alloying Elements ◽  
Sintering Process ◽  
Alloying Element ◽  
Cooling Rates ◽  
Advantages And Disadvantages ◽  
Master Alloys ◽  
Oxygen Sensitive ◽  
Cct Diagrams

Abstract In powder metallurgy (PM), there are several ways of introducing alloying elements into a PM material in order to adjust a certain alloying element content. Each alloying route has its advantages and disadvantages. Master alloys (MA), powders with a high content of typically several alloying elements, can be added in small amounts to a base powder, especially to introduce oxygen sensitive elements such as Cr, Mn, and Si. In addition, the master alloy can be designed in such a way that a liquid phase is formed intermediately during the sintering process to improve the distribution of alloying elements in the material and to accelerate homogenization. In this study, such master alloys were combined with pre-alloyed base powders to form hybrid alloyed mixtures with the aim of improving the material‘s sinter hardenability. The hybrid alloys were compared with mixtures of master alloy and plain Fe as reference material. The sinter hardenability of all materials was determined by generating CCT diagrams recorded with 13 different cooling rates. These were verified by metallographic cross-sections of specimens treated at common cooling rates of 3 and 1.5 K/s and subsequent hardness measurements of the microhardness (HV 0.1) of the microstructural constituents and the apparent hardness (HV 30). ◼

scholarly journals Effect of cooling rates of production process of Al-3%B-3%Sr master alloy on grain refinement and eutectic modification efficiency in cast A356 alloy

2018 ◽  
Vol 192 ◽  
pp. 01036
Author(s):  
Krittee eidhed ◽  
Phisith muangnoy
Keyword(s):  
Grain Size ◽  
Grain Refinement ◽  
Master Alloy ◽  
Eutectic Silicon ◽  
A356 Alloy ◽  
Holding Time ◽  
Experimental Result ◽  
Cooling Rates ◽  
Eutectic Modification ◽  
Master Alloys

In this paper, size and morphology of the grain refiner and modifier particles in the Al-3%B-3%Sr master alloy production by using different cooling rates were investigated. Two Al-3%B-3%Sr master alloys were produced with 0.2 and 10°C/s, respectively. The grain refinement and eutectic modification efficiency of the Al-3%B-3%Sr master alloy were tested in casting process of A356 alloy by addition of 4wt.% and holding times for 10-120 min. The experimental result showed that microstructure of the M1 alloy (Slow cooling) consisted of larger solidified particles of AlB2, SrB6 and Al4Sr in the matrix of α-Al compared to the M2 alloy (Rapid cooling). The addition of the M1 alloy in cast A356 alloy, it was found that small grain size and fully modify eutectic silicon were obtained from the holding time in a range of 10-60 min. While the addition of M2 alloy, a small grain size was achieved in shorter holding time in a range of 10-30 min but the eutectic silicon was partly modify. From the thermal analyzed result, solidification of un-modified A356 alloy was changed after addition of Al-3%B-3%Sr master alloy. It was clearly observed that both the undercooling of nucleation and eutectic reaction was reduced and the solidification time was shifted to longer.

INFLUENCE OF METHODS FOR ALTI MASTER ALLOY PRODUCTION ON ITS STRUCTURE AND EFFICIENCY IN ALUMINUM ALLOY MODIFICATION

2018 ◽  
pp. 45-52
Author(s):  
K. V. Nikitin ◽  
I. Yu. Timoshkin ◽  
V. I. Nikitin
Keyword(s):  
Electrical Conductivity ◽  
Cast Iron ◽  
Master Alloy ◽  
Alloy Structure ◽  
Cooling Rates ◽  
Master Alloys ◽  
Chill Mold ◽  
Modifying Effect ◽  
Determination Methods ◽  
Iron Mold

A comparative study on the effect of methods for obtaining AlTi4 modifying master alloys on the sizes of Al3Ti intermetallics is made. It is found that increasing cooling rates at solidification from 10–15 °C/s (crystallization in a hot cast iron mold, a plate 30 mm in thickness) to 60–65 °C/s (crystallization in a cold cast iron chill mold, a rod 20 mm in diameter, 170 mm in length) reduces the length and thickness of needle-shaped intermetallics almost twice (397×23 to 215×13 μm). At the same time, lower electrical conductivity and higher alloy density in a solid state are observed. Melt modification with 0,5 wt.% magnesium addition causes the formation of homogeneous 98×3 μm fine-needle intermetallics. The addition of magnesium slightly reduces electrical conductivity and density compared with the AlTi4 master alloy crystallized at the same cooling rate (60–65 °C/s). Modification of A97 grade aluminum and AK9ch alloy (Al–Si–Mg system) with the specified master alloys at the same amount of titanium added (0,01 wt.%) exerts hereditary influence on the density and electrical conductivity, and macrograin (A97) and dendrites of aluminium (AK9ch). The maximum modifying effect is provided by the AlTi4 master alloy containing 0,5 wt.% magnesium. When introduced into the alloy, it contributes to the formation of 10 μm aluminum dendrites 1427 pcs/mm2 in total in the alloy structure. When the AK9ch alloy is modified with the master alloy crystallized at cooling rates of 10–15 °C/s, 28 μm dendrites 672 pcs/mm2 in total are formed in the alloy structure. It is suggested to use density and electrical conductivity determination methods for express evaluation of master alloy modifying effectiveness.

The influence of gadolinium on Al–Ti–C master alloy and its refining effect on AZ31 magnesium alloy

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Wenxue Fan ◽  
Hai Hao
Keyword(s):  
Mechanical Properties ◽  
Magnesium Alloy ◽  
Grain Refinement ◽  
Magnesium Alloys ◽  
Master Alloy ◽  
Cast Alloy ◽  
Az31 Magnesium Alloy ◽  
Synthesis Mechanism ◽  
Refining Effect ◽  
Master Alloys

Abstract Grain refinement has a significant influence on the improvement of mechanical properties of magnesium alloys. In this study, a series of Al–Ti–C-xGd (x = 0, 1, 2, 3) master alloys as grain refiners were prepared by self-propagating high-temperature synthesis. The synthesis mechanism of the Al–Ti–C-xGd master alloy was analyzed. The effects of Al–Ti–C-xGd master alloys on the grain refinement and mechanical properties of AZ31 (Mg-3Al-1Zn-0.4Mn) magnesium alloys were investigated. The results show that the microstructure of the Al–Ti–C-xGd alloy contains α-Al, TiAl3, TiC and the core–shell structure TiAl3/Ti2Al20Gd. The refining effect of the prepared Al–Ti–C–Gd master alloy is obviously better than that of Al–Ti–C master alloy. The grain size of AZ31 magnesium alloy was reduced from 323 μm to 72 μm when adding 1 wt.% Al–Ti–C-2Gd master alloy. In the same condition, the ultimate tensile strength and elongation of as-cast alloy were increased from 130 MPa, 7.9% to 207 MPa, 16.6% respectively.

scholarly journals Microstructures and Macrosegregation of Al–Zn–Mg–Cu Alloy Billet Prepared by Uniform Direct Chill Casting

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 708
Author(s):  
Li Zhou ◽  
Yajun Luo ◽  
Zhenlin Zhang ◽  
Min He ◽  
Yinao Xu ◽  
...  
Keyword(s):  
Mold Wall ◽  
Direct Chill ◽  
Element Distribution ◽  
Direct Chill Casting ◽  
Electromagnetic Stirring ◽  
Alloying Elements ◽  
Alloying Element ◽  
Casting Method ◽  
Chill Casting ◽  
Cu Alloy

In this study, large-sized Al–Zn–Mg–Cu alloy billets were prepared by direct chill casting imposed with annular electromagnetic stirring and intercooling; a process named uniform direct chill casting. The effects of uniform direct chill casting on grain size and the alloying element distribution of the billets were investigated and compared with those of the normal direct chill casting method. The results show that the microstructures were refined and the homogeneity of the alloying elements distribution was greatly improved by imposing the annular electromagnetic stirring and intercooling. In uniform direct chill casting, explosive nucleation can be triggered, originating from the mold wall and dendrite fragments for grain refinement. The effects of electromagnetic stirring on macrosegregation are discussed with consideration of the centrifugal force that drives the movement of melt from the central part towards the upper-periphery part, which could suppress the macrosegregation of alloying elements. The refined grain can reduce the permeability of the melt in the mushy zone that can restrain macrosegregation.

Hardenability of Medium Carbon Cr-Mn-Mo Alloyed Steels

2019 ◽  
Vol 946 ◽  
pp. 341-345
Author(s):  
Mikhail V. Maisuradze ◽  
Maksim A. Ryzhkov
Keyword(s):  
Cooling Rate ◽  
Structural Steels ◽  
Alloying Elements ◽  
Metallographic Analysis ◽  
Medium Carbon ◽  
Austenite Transformation ◽  
Continuous Cooling ◽  
Different Content ◽  
Cct Diagrams

Three medium carbon Cr-Mn-Mo structural steels with different content of alloying elements were studied. The austenite transformation during continuous cooling was investigated using dilatometer and metallographic analysis. The CCT diagrams were plotted showing the effect of the increased alloying elements content and B and Nb micro-alloying on the hardenability of the studied steels. The hardness dependences on the cooling rate were obtained.

Self-propagating high-temperature synthesis microalloying of MoSi2 with Nb and V

2003 ◽  
Vol 18 (8) ◽  
pp. 1842-1848 ◽  
Author(s):  
F. Maglia ◽  
C. Milanese ◽  
U. Anselmi-Tamburini ◽  
Z. A. Munir
Keyword(s):  
Solid Solution ◽  
High Temperature ◽  
Tetragonal Phase ◽  
Synthesis Method ◽  
The Self ◽  
Alloying Elements ◽  
Alloying Element ◽  
Temperature Synthesis ◽  
Starting Mixture ◽  
High Temperature Synthesis

Microalloying of MoSi2 to form Mo(1−x)MexSi2 (Me = Nb or V) was investigated by the self-propagating high-temperature synthesis method. With alloying element contents up to 5 at.%, a homogeneous C11b solid solution was obtained. For higher contents of alloying elements, the product contained both the C11b and the hexagonal C40 phases. The relative amount of the C40 phase increases with an increase in the content of alloying metals in the starting mixture. The alloying element content in the hexagonal C40 Mo(1−x)MexSi2 phase was nearly constant at a level of about 12 at.% for all starting compositions. In contrast, the content of the alloying elements in the tetragonal phase is considerably lower (around 4 at.%) and increases slightly as the Me content in the starting mixture is increased.

scholarly journals Is ink heating a relevant concern in the High Speed Sintering process?

2021 ◽  
Author(s):  
Rhys J. Williams ◽  
Patrick J. Smith ◽  
Candice Majewski
Keyword(s):  
Cross Sections ◽  
Inkjet Printing ◽  
High Speed ◽  
Sintering Process ◽  
Significant Drop ◽  
Powder Bed ◽  
Consistent Manner ◽  
Fluid Properties ◽  
Different Temperatures ◽  
Accuracy And Repeatability

AbstractHigh Speed Sintering (HSS) is a novel polymer additive manufacturing process which utilises inkjet printing of an infrared-absorbing pigment onto a heated polymer powder bed to create 2D cross-sections which can be selectively sintered using an infrared lamp. Understanding and improving the accuracy and repeatability of part manufacture by HSS are important, ongoing areas of research. In particular, the role of the ink is poorly understood; the inks typically used in HSS have not been optimised for it, and it is unknown whether they perform in a consistent manner in the process. Notably, the ambient temperature inside a HSS machine increases as a side effect of the sintering process, and the unintentional heating to which the ink is exposed is expected to cause changes in its fluid properties. However, neither the extent of ink heating during the HSS process nor the subsequent changes in its fluid properties have ever been investigated. Such investigation is important, since significant changes in ink properties at different temperatures would be expected to lead to inconsistent printing and subsequently variations in part accuracy and even the degree of sintering during a single build. For the first time, we have quantified the ink temperature rise caused by unintentional, ambient heating during the HSS process, and subsequently measured several of the ink’s fluid properties across the ink temperature range which is expected to be encountered in normal machine operation (25 to 45 ∘C). We observed only small changes in the ink’s density and surface tension due to this heating, but a significant drop (36%) in its viscosity was seen. By inspection of the ink’s Z number throughout printing, it is concluded that these changes would not be expected to change the manner in which droplets are delivered to the powder bed surface. In contrast, the viscosity decrease during printing is such that it is expected that the printed droplet sizes do change in a single build, which may indeed be a cause for concern with regard to the accuracy and repeatability of the inkjet printing used in HSS, and subsequently to the properties of the polymer parts obtained from the process.

A High Effective and Low-Cost Modifier for Hypereutectic Al-Si Alloys

2013 ◽  
Vol 721 ◽  
pp. 282-286
Author(s):  
Guang Hui Qi
Keyword(s):  
Grain Size ◽  
Master Alloy ◽  
Low Cost ◽  
Environment Pollution ◽  
Casting Method ◽  
Good Future ◽  
Primary Si ◽  
Average Grain Size ◽  
Master Alloys

In order to settle environment pollution and provide a high effective and low-cost modifier for refining the primary Si in hypereutectic Al-Si alloys, Al-Fe-P master alloys containing 2.0~5.0% phosphorus have been invented by casting method. The Al-Fe-P master alloys can be conveniently produced and an excellent modification can be obtained by adding 0.3~0.8wt% Al-Fe-P master alloy in Al-Si alloys containing 12%-25% Si at a relatively lower modifying temperature. The number of primary Si increases obviously and the average grain size of primary Si decreases largely, less than 50μm. Furthermore Al-Fe-P master alloys have many advantages, such as low cost, convenient operation technology, no pollution, stable and long-term modification effect, easy storage and etc. Al-Fe-P master alloys have overcome the shortages of current modifier and have a good future for hypereutectic Al-Si alloy modification.

Effect of boron on the continuous cooling transformation kinetics in a low carbon advanced ultra-high strength steel (A-UHSS)

2012 ◽  
Vol 1485 ◽  
pp. 83-88 ◽  
Author(s):  
G. Altamirano ◽  
I. Mejía ◽  
A. Hernández-Expósito ◽  
J. M. Cabrera
Keyword(s):  
Research Work ◽  
High Strength Steels ◽  
High Strength ◽  
Microstructural Characterization ◽  
Low Carbon ◽  
Transformation Kinetics ◽  
Cooling Rates ◽  
Continuous Cooling Transformation ◽  
Continuous Cooling ◽  
Cct Diagrams

ABSTRACTThe aim of the present research work is to investigate the influence of B addition on the phase transformation kinetics under continuous cooling conditions. In order to perform this study, the behavior of two low carbon advanced ultra-high strength steels (A-UHSS) is analyzed during dilatometry tests over the cooling rate range of 0.1-200°C/s. The start and finish points of the austenite transformation are identified from the dilatation curves and then the continuous cooling transformation (CCT) diagrams are constructed. These diagrams are verified by microstructural characterization and Vickers micro-hardness. In general, results revealed that for slower cooling rates (0.1-0.5 °C/s) the present phases are mainly ferritic-pearlitic (F+P) structures. By contrast, a mixture of bainitic-martensitic structures predominates at higher cooling rates (50-200°C/s). On the other hand, CCT diagrams show that B addition delays the decomposition kinetics of austenite to ferrite, thereby promoting the formation of bainitic-martensitic structures. In the case of B microalloyed steel, the CCT curve is displaced to the right, increasing the hardenability. These results are associated with the ability of B atoms to segregate towards austenitic grain boundaries, which reduce the preferential sites for nucleation and development of F+P structures.

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