Question
Asked 29th Jun, 2016

What is the most ideal metal material?

We are trying to make a metal material more strong and more toughness, but they often act as relation of opposition. Now if there are two kinds of material whose yield strength is the same, but one with a high UTS and a low elongation, the other with a low UTS which is approximately the value with the YS and a high elongation.     Which material is more useful do you think?

Most recent answer

26th Jul, 2016
Lauro Romeiro
Universidade Federal do Rio Grande do Sul
It's difficult to say because depends on what you need mainly between strength and toughness. If strength is more important the metal with higher UTS is more appropriate. If toughness is more more important the metal with higher elongation probably will be better. Nowadays some HSSA (advanced steels) are produced with good strength and good elongation and toughness as TRIP steel and Q&P steels.

Popular answers (1)

29th Jun, 2016
Libor Trško
Research Centre of the University of Žilina
It all depends on the application, mainly loading conditions when you consider mechanical proprties. In case of static loading you should always load the material under the yield point. If you consider cyclic loading higher UTS can be also very tricky. There are no ideal, good or bad materials it all depend on the application.
7 Recommendations

All Answers (20)

29th Jun, 2016
Robert A Hafley
NASA
Your question is too general to be answered without knowing the application, i.e., there is no "ideal" material. 
29th Jun, 2016
P. Van Mourik
Delft University of Technology
Dear Han Tielong,
Suppose that the YS in the cases you mentioned corresponds to the elastic limit. Then the respective values of the Young's modulus determine the magnitude of the elastic deformation, thereby influencing the stiffness of the construction under design (note that stiffness is determined by the Young's modulus as well as by the design). Whether or not a large plastic elongation  is desired, is largely linked to the processing of your metal alloy. I agree with Robert A. Hafley, there are no ideal materials, at least no ideal metal alloys. 
1 Recommendation
29th Jun, 2016
Libor Trško
Research Centre of the University of Žilina
It all depends on the application, mainly loading conditions when you consider mechanical proprties. In case of static loading you should always load the material under the yield point. If you consider cyclic loading higher UTS can be also very tricky. There are no ideal, good or bad materials it all depend on the application.
7 Recommendations
30th Jun, 2016
Tielong Han
Beijing University of Technology
I know that there is no ideal metal materials, I'm just curious about which is more useful of the two materials I mentioned. Thank you for all your answers anyway.
1st Jul, 2016
Dusan Arsic
University of Kragujevac
You can not define absolutely "ideal" material. You should choose metal depending on desired application and exploitation properties you want to achieve.
1 Recommendation
1st Jul, 2016
John Longwell
Corning Community College
Often the plane strain fracture toughness KIc, can be an indicator of usefullness.
2nd Jul, 2016
Liang Lan
Shanghai University of Engineering Science
I feel that there is no evdience of the most ideal metal materials, denpending how to improve to make it more and more excellent.
2nd Jul, 2016
P. Van Mourik
Delft University of Technology
Dear Han Tielong,
It seems to me that some of the participants in the above discussion are a little misled by the rather general character of the bold part of your question. However, the second part thereof regards a rather specific comparison between metal alloys having corresponding values of YS, but different values of plastic elongation: high UTS and small plastic elongation and low UTS and large plastic elongation. Clearly the second metal alloy is much more suited for plastic deformation than the first one. Again, which metal alloy to select depends on subsequent processing and final application.
1 Recommendation
3rd Jul, 2016
Djebli Abdelkader
University of Mustapha Stambouli Mascara / Faculty of Sciences and Technology
Hi dear Han,
Why, not looking for other proprties, that may make différence between your two materials, For example Kc for strong or HV for hard. Try to make a deal among different properties and look what it gives.
1 Recommendation
4th Jul, 2016
M. E. H. Shalabi
Central Metallurgical Research and Development Institute
This  depends on the application. . In case of static loading you should always load rhe material under the yield point. If you consider cyclic loading higher UTS can be also very tricky. That is You must  choose metal depending on desired application and exploitation properties you want to achieve.
2 Recommendations
4th Jul, 2016
Lucas Castro
Universidad a Distancia de Madrid
As everybody has said, it depends on the application.
You can read more about it in Ashby maps.
2 Recommendations
4th Jul, 2016
Mikio Fukuhara
Tohoku University
I favor titanium. Ti has large specific strength, large corrosion proof, small Bauschinger effect and etc. Titanium oxide has also photocatalysis effect in crystal state, and large electric storage with largest work function (5.5 eV) in amorphous state for inorganic materials, and show many kinds of color in its Magneli phases.
1 Recommendation
4th Jul, 2016
Michael Parvin
California State University, Los Angeles
To select a material for a given application the choice should be made with considering cost, weight, strength, etc. This leads to a systematic approach to materials selection that has been developed by F. Crane (Selection and use of Engineering Materials) and M. Ashby (Materials Selection in Mechanical Design). Carne describes an approach that allows you to pick the best materials for any application from a range of the materials for which data are available. Ashby uses a material database and a computerized approach to select the best material from the database.
You need to first develop the material selection index (the lightest, strongest, ...) for the type of loading involved such as stiffness A =( ), fracture toughness B=( ) , tensile strength C=( ), D=Cost, ... etc. You should then tabulate these indices along cost for materials with available data and find an overall rating. 
Overall rating = [A+B+C+...+(1-D)]/n  where n is the number of criteria used.
The material with the highest overall rating is the best for this application. This is well described in Chapter 14 of Cran's book.
The computer software developed by Ashby (CES by GRANTA) has a large database and uses a graphic method that considers all the materials in database when a material is selected.
4 Recommendations
4th Jul, 2016
P. Van Mourik
Delft University of Technology
Dear Han Tielong,
It seems to me that the increasing number of participants broadens the scope of this discussion, thereby passing by your specific question 'Now if there are two kinds of metal alloys whose yield strength are the same, but one with a high UTS and a low elongation, the other with a low UTS which is approximately the value with the YS and a high elongation. Which metal alloy is more useful?' According to me, the answer remains: that depends on the subsequent processing and final application. However, a large plastic elongation hints strongly at a metal alloy suited for processing via cold deformation.
1 Recommendation
5th Jul, 2016
Charles Edward Rowe
Newcastle University
Dear Han Tielong,
As others have answered, it all depends on the temperature of operation, method of loading and the atmosphere you are using.  ASM handbook Vol 20 is a useful source of information as is the GRANTA software mentioned by a previous respondent.
6th Jul, 2016
Hemant Nautiyal
Indian Institute of Technology (Banaras Hindu University) Varanasi
It depends on application,and i agree with michael parvin, however i suggest you can compare the UTS and fracture toughness(i.e J1c and K1c known as plain stress fracture toughness and plain strain fracture toughness respectively whatever is applicable of these two) for various metals and select your metal according to application.However the application is in dynamic loading condition then compare the fatigue crack growth results for toughness.
1 Recommendation
6th Jul, 2016
Joël Saverna
Saint-Brieuc Fonderie , France
Not exactly a high quality answer:
If you ask a Metallurgist, the answer is often "It depends"... This is in the "definition of a Metallurgist": A pseudo scientist, who uses undetermined suppositions, indefinite theories, and inexpressible hypotheses; which are based on unreliable information, uncertain quantities, and incomplete data; derived from non-reproducible experiments and incomplete investigations; using equipment and instruments of questionable accuracy, insufficient resolution, and inadequate sensitivity, to arrive at timid, tentative cloudy, abstruse, and non-committed conclusions prefaced by the phrase, "IT DEPENDS".  
1 Recommendation
9th Jul, 2016
Rijesh Malayathodi
VIT University
There is no ideal metal but metals can be tailor made into your needs by alloying and strengthening.
26th Jul, 2016
Lauro Romeiro
Universidade Federal do Rio Grande do Sul
It's difficult to say because depends on what you need mainly between strength and toughness. If strength is more important the metal with higher UTS is more appropriate. If toughness is more more important the metal with higher elongation probably will be better. Nowadays some HSSA (advanced steels) are produced with good strength and good elongation and toughness as TRIP steel and Q&P steels.

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