Mechanical Properties & Effects Of Alloying Element Prepared by : Patel Karan Patel krunal Patel Mihir Patel Narendra Submitted to: Dhaval Darji

Mechanical properties material  The mechanical properties of the metals are those which are associated with the ability of the material to resist mechanical forces and load. These mechanical properties of the metal include strength, stiffness, elasticity, plasticity, ductility, brittleness, malleability, toughness, resilience, creep and hardness. We shall now discuss these properties as follows : 1. Strength: It is the ability of a material to resist the externally applied forces without breaking or yielding. The internal resistance offered by a part to an externally applied force is called *stress. 2. Stiffness: It is the ability of a material to resist deformation under stress. The modulus of elasticity is the measure of stiffness.

3. Elasticity: It is the property of a material to regain its original shape after deformation when the external forces are removed. This property is desirable for materials used in tools and machines. It may be noted that steel is more elastic than rubber. 4. Plasticity: It is property of a material which retains the deformation produced under load permanently. This property of the material is necessary for forgings, in stamping images on coins and in ornamental work. 5. Ductility: It is the property of a material enabling it to be drawn into wire with the application of a tensile force. A ductile material must be both strong and plastic. 6. Brittleness: It is the property of a material opposite to ductility. It is the property of breaking of a material with little permanent distortion. Brittle materials when subjected to tensile loads, snap off without giving any sensible elongation. Cast iron is a brittle material.

7. Malleability: It is a special case of ductility which permits materials to be rolled or hammered into thin sheets. A malleable material should be plastic but it is not essential to be so strong. The malleable materials commonly used in engineering practice are lead, soft steel, wrought iron, copper and aluminium. 8. Toughness: It is the property of a material to resist fracture due to high impact loads like hammer blows. The toughness of the material decreases when it is heated. It is measured by the amount of energy that a unit volume of the material has absorbed after being stressed upto the point of fracture. This property is desirable in parts subjected to shock and impact loads. 9. Hardness: It is a very important property of the metals and has a wide variety of meanings. It embraces many different properties such as resistance to wear, scratching, deformation and machinability etc. It also means the ability of a metal to cut another metal.

Measurement of properties  We can measure the properties by different method using suitable instrument.  Here are the list of some methods which are commonly used to measure the different properties.  Hardness measurement: Brinell Hardness Instrumented Indentation Knoop Hardness Rockwell Hardness Rubber Hardness Vickers Hardness

 The Rockwell hardness test method is the most commonly used hardness test method. The Rockwell test is generally easier to perform, and more accurate than other types of hardness testing methods. The Rockwell test method is used on all metals, except in condition where the test metal structure or surface conditions would introduce too much variations; where the indentations would be too large for the application; or where the sample size or sample shape prohibits its use.  The Rockwell method measures the permanent depth of indentation produced by a force/load on an indenter. First, a preliminary test force (commonly referred to as preload or minor load) is applied to a sample using a diamond indenter. This force is held for a predetermined amount of time (dwell time) to allow for elastic recovery. This major load is then released and the final position is measured against the position derived from the preload, the indentation depth variance between the preload value and major load value. This distance is converted to a hardness number

Tensile test  Tensile testing, also known as tension testing, is a fundamental materials science test in which a sample is subjected to a controlled tension until failure. The results from the test are commonly used to select a material for an application, for quality control, and to predict how a material will react under other types of forces. Properties that are directly measured via a tensile test are ultimate tensile strength, maximum elongation and reduction in area. From these measurements the following properties can also be determined: Young's modulus, Poisson's ratio, yield strength, and strain-hardening characteristics. Uniaxial tensile testing is the most commonly used for obtaining the mechanical characteristics of isotropic materials. For anisotropic materials, such as composite materials and textiles, biaxial tensile testing is required.

What is alloying element  Metallic or non-metallic elements such as chromium, cobalt, copper, manganese, nickel, silicon, titanium, tungsten, vanadium, zirconium etc. added in specified or standard amounts to a base-metal to make an alloy and to get some desire properties like hardness, strength, brittleness, ductility etc.  We can get desire property or combination of different properties by adding one material into another which is called alloying element.  Some alloying element are listed below with their effect on the other material after alloying it.

Effects of Alloying Element: 1. Chromium:  It improves hardness, hardenability, wear and corrosion resistant.  It also improve elevated temperature behaviour of steel. 2. Nickel:  It improves toughness, ductility and strength.  It reduce distortion during heat treatment.

3. Manganese:  It improves strength of steel in both hot rolled and heat treated conditions. 4. Silicon:  It is used as deoxidizing agent for steels improving elastic limit and resilience. 5.Molybdenum:  It improves hardenability, hardness, toughness, high temperature strength.

6. Tungsten:  It improves hardness and toughness.  It maintains hardness even at red heat, and hence it is widely used in tool steels.  Its effect is similar to that of molybdenum, except that it must be added in greater quantities.

Case study  Recent research and development in titanium alloys for biomedical applications and healthcare goods regarding healing process in bone.  Titanium alloys for biomedical titanium alloys : Since the population ratio of the aged people is rapidly growing, the number of the aged people demanding replacing failed tissue with artificial instruments made of biomaterials is increasing. In particular, the amount of usage of instruments for replacing failed hard tissues such as artificial hip joints, dental implants, etc. is increasing among the aged people. Metallic biomaterials are the most suitable for replacing failed hard tissue up to now. Main metallic biomaterials are stainless steels, Co based alloys, titanium and its alloys. Recently, titanium alloys are getting much attention for biomaterials because they have excellent specific strength and corrosion resistance, no allergic problems and the best biocompatibility among metallic biomaterials. Pure titanium and Ti–6Al–4V are still the most widely used ones for biomedical applications among the titanium alloys. They occupy almost of the market of titanium biomaterials. However, these are basically developed as structural materials mainly for aerospace structures.

 Research and development of titanium alloys fo biomedical applications from the beginning were started fairly recently. In that case, the elements, which are judged to be non-toxic and non-allergic through the reported data of cell viability for pure metals, polarization resistance (corrosion resistance) and tissue compatibility of pure metals and representative metallic biomaterials, and allergic properties of pure metals, are selected as alloying elements for titanium. As a result, Nb, Ta and Zr are selected as the safest alloying elements to titanium. In addition to these elements, Mo and Sn are selected as safer elements for living body.

 Mechanical biocompatibility of low rigidity titanium alloys for biomedical applications : In order to confirm the advantage of low rigidity for bone healing and remodeling, using rabbits, experimental tibial fracture was induced in tibia by oscillating saw at just below the tibial tuberosity. Intramedullary rod made of low rigidity Ti–29Nb–13Ta–4.6Zr, Ti–6Al–4V ELI or SUS 316L stainless steel was inserted into the intramedullary canal to fix the fracture. Bone healing, remodeling and atrophy was observed by X-ray transmission image every 2 weeks up to 24 weeks. The outline of fracture callus was very smooth with bone remodeling in Ti–29Nb– 13Ta–4.6Zr. Similar phenomenon was observed at 8 weeks in Ti–6Al–4V ELI and SUS 316L. In Ti–29Nb–13Ta–4.6Zr, the amount of the fracture callus was relatively small, and gradually decreased from 6 weeks, and then there were no traces of fracture at 10 weeks after the fixation. After 10 weeks, no changes could be observed up twas observed at the posterior tibial bone after 20 weeks. In Ti–6Al–4V ELI, the callus formation and the bone remodeling were almost similar to those in Ti–29Nb–13Ta–4.6Zr, but slower as compared with Ti–29Nb–13Ta– 4.6Zr. A little atrophic change was seemed to be observed at 18 weeks. In SUS 316L stainless steel, a large amount of the fracture callus was observed, and remains up to the end of the succeeding period. Bone atrophy seemed to be occurring at the posterior proximal tibial bone at 10 weeks, and became obvious every 2 weeks. The posterior tibial bone became to be very thin at 24 weeks. Therefore, low rigidity titanium alloy, Ti–29Nb–13Ta–4.6Zr, is found to improve the load transmission issue of the current metal implants with the high rigidity.o 18 weeks. However, a little atrophic change

conclusion the amount of the fracture callus was relatively small, and gradually decreased from 6 weeks, and then there were no traces of fracture at 10 weeks after the fixation. After 10 weeks, no changes could be observed up to 18 weeks. However, a little atrophic change was observed at the posterior tibial bone after 20 weeks bone atrophy seemed to be occurring at the posterior proximal tibial bone at 10 weeks, and became obvious every 2 weeks. The posterior tibial bone became to be very thin at 24 weeks. Therefore, low rigidity titanium alloy, is found to improve the load transmission issue of the current metal implants with the high rigidity.