Influence of ECAP-Back Pressure on the Porosity Distribution

This work was devoted to the description of the effect of alloying by transition metals (Cr, Cu, Fe) on the structure and properties of TiAl15Si15 alloy. Alloying elements does not form separate phases, being dissolved in titanium silicide or aluminide. Cu was found predominantly in aluminide phase, while iron was found to bethe silicide-former. Chromium dissolved in both aluminide and silicide in almost comparable amounts. All applied alloying elements increased the wear resistance, but reduced the room-temperature compression strength. The addition of iron and chromium strongly increase the thermal stability at 1000°C by stabilizing the silicide phase.Keywords: reactive sintering; mechanical properties testing; intermetallic compounds; oxidation 1 Introduction Alloys based on titanium aluminides (Ti 3 Al and TiAl) are modern materials for hightemperature applications. Due to low density, good mechanical properties and oxidation resistance at high temperatures, these alloys already found its application in the aerospace industry. The application limits of Ti 3 Al phase are 760°C in inert atmosphere (creep limit) and approx. 600°C in air (oxidation limit) [1]. Application range of TiAl phase is 750°C in air and approx. 900°C in inert atmosphere or vacuum [1]. It shows that the temperature range of application of all Ti-Al phases is strongly limited by their high-temperature oxidation. To improve the high-temperature oxidation behaviour of these materials, additions of various alloying elements are applied. Previously, it was reported that niobium and tantalum increase the high-temperature oxidation resistance [2] and creep behaviour [3] of Ti-Al alloys. It led to the development of new generation of Ti-Al alloys [4]. However these heavy and expensive elements undesirably increase the density and cost. Other possibility how to improve hightemperature behaviour is alloying with silicon. When Ti-Al-Si alloys are produced by conventional melting metallurgy techniques, coarse sharp-edged particles of Ti 5 Si 3 silicide are formed, having negative impact on mechanical properties such as ductility or fracture toughness. Simple production route leading to the fine structure is a reactive sintering powder metallurgy. In our previous works [5], [6], production route for Ti-Al-Si alloys with aluminium content between 8 and 20 wt. % and silicon in the range of 10-20 wt. % was developed and roomtemperature properties were described [5]. There are many papers dealing with the influence of various alloying elements on the structure and selected properties of Ti-Al and Ti-Si binary alloys. In addition to the effect of Nb and Ta,

“…This behaviour is completely different from the formation of porosity during annealing in e.g. ECAP process [14,15]. The hardness of the ternary TiAl15Si15 is 1180 HV 10 (Fig.3).…”

Section: Experimental Materials and Conditionsmentioning

confidence: 87%

EFFECT OF ALLOYING ELEMENTS ON PROPERTIES OF PM Ti-Al-Si ALLOYS

Novák¹,

Kříž²,

Michalcová³

et al. 2013

“…Also the role of porosity represent the problem related to the mechanical properties. The investigation of the porosity behavior of aluminum alloys is reported in [24][25][26][27].…”

Section: Microstructure and Mechanical Propertiesmentioning

confidence: 99%

Laser Powder Bed Fusion of Aluminum Alloys

Manfredi¹,

Bidulský²

2017

The aim of this study is to analyze and to summarize the results of the processing of aluminum alloys, and in particular of the Al-Si-Mg alloys, by means of the Additive Manufacturing (AM) technique defined as Laser Powder Bed Fusion (L-PBF). This process is gaining interest worldwide thanks to the possibility of obtaining a freeform fabrication coupled with high mechanical strength and hardness related to a very fine microstructure. L-PBF is very complex from a physical point of view, due to the extremely rapid interaction between a concentrated laser source and micrometric metallic powders. This generate very fast melting and subsequent solidification on each layer and on the previously consolidated substrate. The effects of the main process variables on the microstructure and mechanical properties of the final parts are analyzed: from the starting powder properties, such as shape and powder size distribution, to the main process parameters, such as laser power, scanning speed and scanning strategy. Furthermore, some examples of applications for the AlSi10Mg alloy are illustrated.

“…The Equal Channel Angular Pressing (ECAP) method is based on the dislocation activities and is configuration during increased deformation degree [3][4][5][15][16][17][18][19]. In Fig.…”

Section: The Principle Of Equal Channel Angular Pressingmentioning

confidence: 99%

Structure and Properties of Az31 Magnesium Alloy After Combination of Hot Extrusion and Ecap

Hilšer

Rusz

Maziarz

et al. 2017

Equal channel angular pressing (ECAP) method was used for achieving very fine-grained structure and increased mechanical properties of AZ31 magnesium alloy. The experiments were focused on the, in the initial state, hot extruded alloy. ECAP process was realized at the temperature 250°C and following route Bc. It was found that combination of hot extrusion and ECAP leads to producing of material with significantly fine-grained structure and improves mechanical properties. Alloy structure after the fourth pass of ECAP tool with helix matrix 30° shows a fine-grained structure with average grain size of 2 µm to 3 µm and high disorientation between the grains. More experimental results are discussed in this article.