Tru e str ess-strain curves obt ain ed in te nsion tests at temperatures ranging from -196 0 LO + 100 0 C wit h ingot iron as ann ealed , Jlorrnalized, quenched and tempered, hot-rolled and cold-drawn are presented . Numerous simultaneous load and diameter measurements were made during t he ent ire co urse of each test. The effects of prior thermal and mechanical t reat ment of the iron on the t rue stress-strain relatio ns are disc ussed.Graphs are prese nted showing t he influ ence of t he testing temperature, the ferrite grain size, and t he initial condition of t he iron on the work-hardening characteristics, namely, strain-hardening and strain-aging. The effects of the above factors on yield st ress and ultimate stress, and on true stress a nd tr ue strain at maximu m load and a t fracture, are presented. The twinning of iron in the tests at low te mperatures is briefly discussed .

A st ud y was made of t he action of boron in relation to the hardenability of high-purity alloys varying in carbon content. The effectiveness of boron in enhancing the harden ability of t hese alloys and certain steels is believed to be due to its action in retarding the rate of nucleation of ferri te and carbide while in soli d solution in austenite. The hardenabi li ty of t he boron-treated a ll oys, as determined in terms of the cri tical coolin g rate of small specimens a usteniti zed at a ,vide range of temperatures, varied with t he prior history and with the carbon content. The hardenabili ty of a commer cial boron-treated steel, as determined by the end-quench test, was also sensitive to prior thermal t reatments. Boron was lost in t he decarburized zone of commercial steels, and i ts rate of diffusion apparently is of t he same order of magni tude as that of car bon. The heat t reatment of specim en s of t he alloys and tcel s to produce a boron const it uent and the microstructures of t h e alloys as cast and as h o mo~e ni ze d are described .

A reduction-of-area gage for measuring the chan ge in diameter of cylindrical or notched tension specimens during tests at controll ed temperatures is described. The gage was d esigned especially for use in tests of specimens completely submerge d in a temperature-co ntro ll ed bath at temperatures ranging f rom -196° to + 100° C. The calibration of t his gage showed t hat meas urements can be mad e with a n accuracy of 0.0001 inch . Some res ul ts obtained with t he use of th is gage are illustrated by true stress-tru e stra in cur ves for a nn ealed in got iron, cold-worked n ickel and cold-worked 18:8 ch romium nicke l s t.eel tested in tension at. -188° and -196° C.

Notch~d a nd unnotch e~ teJ.lsile speci mens of annealed commercially pure titanium were slowly stramed to fract ure m smgle-stage tests at -196° to + 100° C. Unnotched tensile sp ecill1 e~s a lso wer e strained in t wo-stage test~ (strained at one temperature unt il just after the maXlmu m load w!1s reacl;ed and t hen stra.llled to fracture at a different temperat ure) to r eveal t he effect of pnor-stram-temper at ure history on t he tensile proper ties of t he titanium . Impact tests were made on Charpy V-notch specimens at -U)6° to + 200° C for a determination of t he impact notch-toughness of the metal. T rue-stress-true-strain relations were determined for t~e t.itan. ium in tension, and a stu d y was r;l ade of the effects of test temperature and the stress cl1strlbutlOn on the rates of work-hardenmg of t he metal.

Unnotchcd and notched specime ns (60° notch angle, 0.05-inch root r adius and various notch dept hs) of an annealed commercially pure t it anium were slowly straine d t o fract ure in te nsion at + 150° or + 100° to -196° C, to reveal the combi ned e ffects of te mperat ure and notc h geomctry o n the te nsile be havior of the metal. Impact tests were made o n Charp y V-notch s pecimens at + 300° to -196° C for a determination of the impact notch-toughness of the tita ni um. Tru e stress-true s train relations were determined for t he t itanium in tensio n and a s tud y was made of the effec ts of test tc m perature, stress systcm, and intersti tial con t e nt o n t he mec hanism of defor mation and work-hardeni ng characteristics of the m etal.